CHEM 103: Ch. 1 & 2
The volume of water in a graduated cylinder is an example of what type of property? (Select all that apply.)
extensive physical Volume is an example of both a physical property and an extensive property because it is dependent on the amount of water in the cylinder (extensive) and it is not associated with a change in chemical composition (physical).
When we measure a mass on a laboratory scale, we are working in the ___________ domain.
macroscopic In the laboratory, when we are doing chemistry in quantities we can see, using tools and instruments we can see, we are working in the macroscopic domain.
Which of the following is an example of a homogenous mixture?
maple syrup Maple syrup is an example of a homogenous mixture.
What would 0.038851 be rounded to if it needed to retain 3 significant figures?
0.0389 The dropped digit is 5 so the number is rounded up to 0.0389 to have 3 significant digits.
How many moles are in 2.3 g of phosphorus?
0.074 mol To calculate the number of moles in 2.3g of phosphorus, divide this mass by the molar mass as follows. 2.3 (1/30.974) = 0.0743 mol
Leading zeros are only significant if they are:
leading zeros are never significant Leading zeros serve to display the magnitude of a value, but they never imply precision, so they are never significant.
Which phase of water has the highest density?
liquid For water, the liquid phase is more dense than the solid, which is why ice floats. A gas is far less dense, as the particles are very far apart.
Which of the following CANNOT be classified as a compound?
lithium Lithium is an element. The rest are made of multiple elements.
Mass
m = density*volume = d*v
A student performs an experiment to determine the molar mass of magnesium oxide. The student repeats the experiment five times and collects the following data: 40.220gmol, 40.654gmol, 40.314gmol, 40.165gmol, and 40.554gmol. What is the sample standard deviation for this set of data? Give the answer with two significant figures.
0.21 To find the sample standard deviation, use the formula sx=sqrt[(1/N-1)∑(Xi-X¯)^2], where N is the number of measurements, xi is the ith measurement, and x¯ is the mean, or average of the measurements. First find the mean. x¯=[40.220+40.654+40.314+40.165+40.554]/5 = 40.3814 Next, subtract the mean from each measurement and square the result to find the values of (xi−x¯)2. i xi (xi-x¯)^2 1 40.220 0.02605 2 40.654 0.07431 3 40.314 0.004543 4 40.165 0.04683 5 40.554 0.02971 Find the sum of the squared differences by adding the numbers in the second column. ∑(xi−x¯)^2 = 0.1815 Divide the sum by N−1, or 4, since there are 5 measurements. 0.1815/4 = 0.04538 Finally, find the standard deviation by taking the square root. sx = 0.21
How many moles of CuSO4 are present in a 45.0 g sample?
0.282 moles 45 (1/159.6 g CuSO4) = 0.282 moles
How many moles of PCl5 are present in a 100.0 g sample?
0.4802 mol To determine the amount of PCl5 in a 100.0g sample, first determine the molar mass of this compound. molar mass of PCl5 = 30.974amu + 5×35.453 amu = 208.239amu Now, divide the mass by the molar mass to to determine the amount of PCl5 in moles. moles of PCl5 = 100.0 g PCl5 × 1 mol PCl5 / 208.239 g PCl5 = 0.48022 mol PCl5 There are 0.4802 mol of PCl5 in a 100.0 g sample.
How many moles are in 22 grams of argon?
0.55 moles 22 g = x moles * 39.948 g/mol x = 0.55 moles
How many total atoms are present in 400. grams of Na2SO4?
1.19*10^25 atoms 400.0 g (1/142.042)(6.022*10^23) = 1.696*10^24 1.696*10^24 (7 atoms) = 1.187*10^25 atoms
110 grams of baking soda (NaHCO3) is equal to how many moles?
1.3 moles grams = moles * molar mass 100 g = x moles * 84.01 g/mol x= 1.31 moles
How many moles of carbon atoms are in 18 g?
1.5 moles 18 (1/12 g) = 1.5 moles
How many moles of LiF are present in a 42.0 g sample?
1.62 moles 42 (1/25.9) = 1.62 moles
The fundamental charge discovered by Millikan has a specific value of:
1.6×10^−19 C The fundamental charge, discovered by Millikan, has a specific value of 1.6×10−19 C.
What is the mass, in grams, of 0.2270 moles Au2O3?
100.3 g Recall that the formula mass of a compound gives the mass of one mole of the compound. Convert the moles of Au2O3 into grams by multiplying by the formula mass, found with the periodic table: 0.2270 (441.931) = 100.318 g
What will be the mass of one mole of carbon atoms?
12 g By definition, one atom of carbon has a mass of 12 amu. One mole of carbon atoms has a mass of 12 g. This is the difference in molar mass and atomic mass. Though they have the same value(in this case, 12) these terms represent different things. Molar mass refers to the mass per mole of substance, and will always have units of g/mol, whereas the atomic mass refers mass of one molecule, or formula unit, and will have units of atm.
of oxygen gas. What mass of water (in grams), if it reacted completely, was initially present? (The electrolysis of water is the use of an electric current to decompose it into its component elements.)
120.0 g Since both the hydrogen and oxygen came from water, the original mass of water must be equal to their sum.
Which of the following has 3 significant figures? Select all that apply.
123 12.3 1.23×10^4 All of the answer choices have 3 significant figures except for 123000. The decimal point at the end of the number means that the trailing zeros are also significant, so it has 6 total.
What is the chemical formula for an atom with 58 protons and 82 neutrons? Include the mass number and the atomic number.
140/57 Ce It is given that the atom has 58 protons and 82 neutrons. The atomic number is equal to the number of protons, so the atomic number is 58, which corresponds to cerium (Ce) on the periodic table. The mass number is equal to the number of protons and neutrons in the nucleus, so the mass number is 58+82=140. The chemical formula for a specific isotope of an element is written as A/Z X, where A is the mass number, Z is the atomic number, and X is the chemical symbol. Therefore, the chemical formula for this isotope of cerium is 140/57 Ce.
Write the formula for an isotope of gold (Au) with 118 neutrons. Include the mass number and the atomic number.
197/79 Au Gold has an atomic number of 79, so there are 79 protons. The mass number is equal to the total number of protons and neutrons in the nucleus, so an isotope of gold with 118 neutrons has a mass number of 79+118=197. The chemical formula for a specific isotope of an element is written as A/Z X, where A is the mass number, Z is the atomic number, and X is the chemical symbol. Therefore, the chemical formula for this isotope of gold is 197/79 Au.
When 5.0 grams of calcium are burned in oxygen, 7.0 grams of calcium oxide result. What mass of oxygen reacted?
2.0 grams The material gained 2.0 grams of mass which must have come from the oxygen.
How many moles of sulfur atoms are there in 64 g of S8?
2.0 moles of S atoms
The isotopes of hydrogen are often referred to by their common names. Write the chemical formula for the isotope deuterium. Include the mass number and the atomic number.
2/1 H Deuterium refers to the isotope of hydrogen with a mass number of 2. The atomic number of hydrogen is 1. So in addition to one proton, deuterium also has one neutron. The chemical formula for a specific isotope of an element is written as A/Z X, where A is the mass number, Z is the atomic number, and X is the chemical symbol. Therefore, the chemical formula for deuterium is 1/2 H.
A train is traveling at 200.kmhr. What is that in ms? Report your answer with the correct number of significant figures.
200 * 1000 * 1/60 * 1/60 = 55.6 m/s
Give the result of the following expression with the correct number of significant figures: 84 m/s * 32.533 s = ?
2732.772 m = 2700 m
How many atoms are present in a water molecule?
3 There are three atoms present in a water molecule: two hydrogen atoms and one oxygen atom.
Complete this calculation to the correct number of significant figures: 5.4589−2.33
3.13 When adding and subtracting, round your answer so it has the same number of decimal places as the value with the least number of decimal places.
What is the mass in grams of 1.00×106 sodium atoms?
3.82*10^-17 grams To determine the mass of 1.00×106 sodium atoms, divide by Avogadro's number and multiply by the molar mass of sodium. 1.00×10^6 (1/6.022×10^23)(22.990) = 3.818×10^−17 g Therefore, after rounding to three significant figures, we find that the mass of 1.00×10^6 sodium atoms is about 3.82×10^−17g.
A sample of sulfur trioxide (SO3) weighs 5100 g. How many molecules are contained in this sample? Use 80.063g/mol for the molar mass of SO3.
3.8×10^25 molecules. 5100g (1/80.063) = 63.70 mol 63.70 (6.022*10^22) = 3.836*10^25 molecules
What is the average mass in grams of one uranium atom (U)?
3.953*10^-22 g 1 atom (1/6.022*10^23)(238.029) = 3.953*10^-22 g
How many grams of helium are in a balloon with 8.40 mol of helium atoms?
33.6 g 8.4 mol (4.003 g) = 33.625 g
Which of the following measurements would be a reasonable guess for the diameter of a gold atom?
3×10^-10 m Atoms are microscopic particles that require specialized microscopes to visualize. Of the four lengths presented, only 3×10−10 m fits this description. The next shortest length, 3×10−3 m, is equal to 3 millimetres and can be seen by the naked eye.
How many significant figures are in the the value 0.00004050? Report your answer as a whole number without decimal places.
4 Non-zero digits, zeros in between non-zero digits, and all trailing zeros to the right of decimal point are significant. However, leading zeros are not significant.
What is the mass in grams of 1.900×1024 iodine atoms?
400.4 1.9*10^24 (1/6.022*10^23) = 3.1551 mol 3.1551 (126.904 g) = 400.39 g
What is the formula mass in atomic mass units for NaF?
41.988 amu Use the periodic table to get the atomic mass of each element. Multiply the atomic mass of the element by the number of atoms of that element in the compound. mass of Na: 22.990×1=22.990 mass of F: 18.998×1=18.998 Add the mass of each element to find the total. 22.990+18.998=41.988 Notice that subscripts in formulas (indicating numbers of atoms) are exact, so they do not constrain the number of significant figures.
Complete this calculation to the correct number of significant figures: 2.33×18
42 When multiplying or dividing, round your answer so it has the same number of significant figures as the value with the least number of significant figures.
What is the mass of a sample of barium carbonate (BaCO3) that contains 21.30mol?
4203 g To calculate the mass of barium carbonate given the number of moles in the sample, multiply the number of moles by the molar mass as follows. 21.30 (197.336) = 4,203.3 g
If you are traveling at 49.00 miles per hour, what is your speed in feet per second? (1 mile=5280 ft) Report your answer with four significant figures.
49 * 1/60 * 1/60 * 5280 = 71.87 fps
How many carbon atoms are there in the empirical formula corresponding to C10H22O2?
5 The simplest formula for a compound is the empirical formula. The empirical formula for this compound is C5H11O. Therefore, there are 5 carbon atoms in the empirical formula for C10H22O2
Calculate the number of atoms in 37.1 grams of LiBr.
5.14 * 10^23 atoms 37.1*(1/86.844 g) (6.022*10^23) = 2.573*10^23 2.573*10^23 (2 atoms) = 5.145*10^23 atoms
Avogadro's number
6.022 x 10^23 mol^-1
Which of the following accurately represents Avogadro's number?
6.022 × 10^23 Avogadro's number is a constant, representing the number of items in a mole. It is equal to 6.022 × 10^23
There are ________ atoms of calcium in a 40.08 gram sample.
6.022×10^23 40.08 g(1 mol Ca40.08 g)(6.022×1023atoms) = 6.022×1023 atoms
Which of the following is equivalent to a mole of carbon atoms?
6.022×10^23 carbon atoms A mole of carbon atoms is equivalent to 6.022×10^23 carbon atoms. In fact, 1 mole of any substance will contain 6.022×10^23 items because that is the definition of a mole.
Calculate the number of total atoms in 195 grams of Ni(OH)2.
6.33*10^24 195g (1/92.707g)(6.022*10^23) = 1.27*10^24 1.27*10^24 (5 atoms) = 6.33*10^24
What is the mass of nitrogen gas (N2) in a sample that contains 21.5mol of nitrogen gas.
602 g To calculate the mass of a sample that contains 21.5mol of N2, multiply the number of moles by the molar mass of N2. 21.5 (28.014) = 602.3 g
What is the mass number of an isotope of copper with 34 neutrons?
63 The mass number is equal to the number of protons and neutrons in the nucleus. Copper has an atomic number of 29, so it must have 29 protons. It is given that there are 34 neutrons, so the mass number is 29+34=63.
Copper exists in two naturally occurring isotopes. The average atomic weight of copper is 63.546 amu. If 69.15% exists as 63Cu with an atomic mass of 62.92, then what is the atomic mass of the second isotope?
64.95 amu An average atomic mass is found by taking a weighted average; the mass of each isotope multiplied by its own abundance toward the total. Knowing that one isotope is responsible for 69.15% of the mass, the remaining isotope must account for the other 30.85%. The average atomic mass will be the sum of the weights of the two isotopes. Let x represent the unknown mass of the second isotope. 63.546 = (0.6915*62.92)+(0.3085x) x=20.0368/0.3085=64.949 amu
A set of measurements was taken 3 times. Determine which of the following sets is both accurate and precise if the accepted value is 68.1 mL.
68.1 mL, 68.0 mL, 68.2 mL The true value is 68.1 mL so the answer choice that has values that are close to the true value and close to each other is the one that can be considered a set that is both accurate and precise.
Which of the following statements about atoms and molecules are true? Select all that apply.
Atoms in a molecule are held together by chemical bonds. All molecules are composed of atoms. A molecule is defined as two or more atoms joined by strong forces called chemical bonds.
Lithium occurs naturally as 6/1 Li and 7/1 Li. Given that lithium's average atomic mass is 6.94 amu, determine which isotope is more abundant.
7/1 Li The atomic mass of each isotope is close to the mass number (a whole number by definition) because each proton and neutron in a nucleus adds about 1 amu to the mass. For elements with many stable isotopes, there is not enough information to determine the most abundant isotope from just the average atomic mass, but if we know that there are only two naturally occurring isotopes that contribute to the average atomic mass, then the more abundant isotope must be the one closer in mass to the average. This is because the average atomic mass is a weighted average. If the isotopes were present in equal amounts, the average atomic mass would be the simple average of each isotope's mass, or about 6.5 amu. Because the weighted average is actually about 6.94 amu, which is much closer to 7 than to 6, there must be more lithium-7 than lithium-6.
How many grams of oxygen are needed to combust 20.0 grams of propane (C3H8)? (use the reaction below to answer the question) C3H8+5O2⟶3CO2+4H2O
72.6 g O2 20 (1/44.10 g C3H8)(5 mole O2)(32 g O2) = 72.6 g O2
How many moles of hydrogen atoms are there in 120 g of C6H12O6
8.0 moles Total Molar Mass = Molar Mass * # Atoms Htot = 1.006 * 12 = 12.096 Ctot = 12.011 * 6 = 72.066 Otot = 15.999 * 6 = 95.994 Total = 180.156 120 g C6H12O6 (1/180.156) = 0.6661 moles 0.6661 (12 H) = 8.0 moles H
How many moles are in 2141 grams of magnesium?
88.09 moles 2141g = x moles * 24.305 g/mol x = 88.09 moles
Which of the following factors used in a dimensional analysis calculation have a finite number of significant figures (in other words, they are not exact numbers) that might limit the precision of the calculated value?
A measurement of speed equaling (27.7 km/hour) Unit conversion factors are almost always exact numbers. For example, there are exactly 1000 m in 1 km because that is how the kilometer is defined. There is no uncertainty involved in the conversion factor, so it will not affect the number of significant figures in our answer. But when using actual measurements, the number of significant figures will have an impact on our calculation.
Which of the following is true regarding significant figures?
All nonzero digits are considered significant.
Which of the following does not change if the sample size changes?
An intensive property An intensive property does not change if the sample size changes.
Whose view that matter is infinitely divisible was considered correct for most of the last two millennia?
Aristotle Aristotle believed that everything was comprised of earth, air, water, and fire, which were infinitely divisible.
Which of the following is true according to Dalton's atomic theory?
Atoms cannot be created or destroyed. As far as Dalton was concerned, atoms cannot be created or destroyed.
Joey has written out the following reaction: 2H2+O2→H2O. Which of Dalton's atomic theory postulates is violated in this incorrect formula?
Atoms cannot be created or destroyed. This formula violates the postulate that atoms cannot be created or destroyed because on the left there are four hydrogen atoms and on the right there are only two.
Which is a possible molecular formula for a molecule with the empirical formula CH2O?
C12H24O12 This is the only option that maintains the precise ratios in the empirical formula.
If compound's formula mass was experimentally determined to be 58, the chemical formula could be:
C3H6O Use the periodic table to get the atomic masses of each element. Then you can calculate the formula mass as such: H=1.008×6=6.048 C=12.011×3=36.033 O=15.999×1=15.999 Adding these together we get 58.080, which rounds to 58 if the mass of the compound is only known to two significant figures.
If the empirical formula for a compound is C3H8, which of the following are possible molecular formulas? Select all that apply.
C3H8 C6H16 If the empirical formula for a compound is C3H8 then the molecular formula can be a compound with multiples of these numbers of atoms. C3H8 and C6H16 are possible molecular formulas.
A molecule of butene consists of 4 carbon atoms and 8 hydrogen atoms. What is butene's empirical formula?
CH2 Butene's empirical formula is CH2, as it has the lowest whole number ratio that is in proportion with C4H8.
Cyclobutane consists of 4 atoms of carbon and 8 atoms of hydrogen. What is cyclobutane's empirical formula?
CH2 The empirical formula must feature the simplest whole-number ratio of the constituent elements. The simplest form of the carbon: hydrogen ratio, given as 4:8, is 1:2. Therefore, the empirical formula is CH2.
A molecule of pentene consists of 5 carbon atoms and 10 hydrogen atoms. What is pentene's empirical formula?
CH2 The empirical formula must feature the simplest whole-number ratio of the constituent elements. The simplest form of the carbon: hydrogen ratio, given as 5:10, is 1:2. Therefore, the empirical formula is CH2.
The molecular formula for glucose is C6H12O6. What is the empirical formula?
CH2O
The molecular formula of glucose is C6H12O6. What is the empirical formula for glucose?
CH2O The empirical formula is the lowest whole number ratio of atoms in a molecule. The molecule glucose has 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms. Since all numbers are divisible by 6, the formula can be simplified to CH2O, which is in the same ratio as C6H12O6.
How could Antoine Lavoisier, the French scientist credited with proposing the law of conservation of matter, have demonstrated this law?
Carefully measuring the mass of reactants before a reaction and the mass of the products after a reaction in a sealed system. Antoine Lavoisier is credited with proposing the law of conservation of matter. He performed experiments where he meticulously measured the masses of reaction reactants and products in a sealed system, so that no gas could escape. His demonstration that the mass of the reactants was equal to the mass of products supported the law of conservation of matter.
The boiling point of water in Celsius is?
Celsius is based around the melting point and boiling point of water, at 0∘C and 100∘C, respectively.
A compound is a chemical substance composed of two or more kinds of elements in a fixed ratio. By what means can the components of a compound be separated?
Chemical means A compound cannot be separated into its component elements by physical means, but it can be separated into its component elements by chemical means.
Which of the following could be considered a chemical change?
Coal burning. Phase changes and mixing of substances are physical processes. When coal burns, carbon atoms form new chemical bonds to oxygen atoms, which is a chemical process.
Density
D = mass/volume = m/v
Who was the first person to propose the existence of the atom?
Democritus Democritus was the first to suggest that everything is made of "atomos", which are the smallest indivisible unit of matter.
Who was the first to propose the idea of atoms?
Democritus The idea of Democritus was actually criticized by others of his time.
Which is an intensive property? Mass Shape Length Density
Density No matter how much of a substance is present, it will have the same density. The other characteristics will change according to the quantity.
Intensive properties can be: Physical properties Chemical properties Either physical OR chemical properties None of the above
Either physical or chemical properties Intensive properties can be either physical, like color, or chemical, like combustibility.
Who determined the structure of the atomic nucleus?
Ernest Rutherford Rutherford elucidated the structure of the atomic nucleus in his gold foil experiment.
Which of the following properties is dependent on the amount of matter present? Intensive Extensive Chemical Physical
Extensive Extensive properties depend on the amount of matter present
_______ properties depend on the amount of matter that is being measured.
Extensive Extensive properties depend on the amount of matter that is being measured.
Which of the following is an example of a chemical property? Flammability Toxicity Acidity Density
Flammability Toxicity Acidity The change of one type of matter into another type (or the inability to change) is a chemical property. Examples of chemical properties include flammability, toxicity, acidity, reactivity (many types), and heat of combustion.
The word "atom" is derived from which language?
Greek Atom is derived from the Greek word "atomos" meaning "uncuttable".
James drops a wooden block into a tank of water and notices that it floats. He then cuts the block in half, drops the block into the same tank and once again the block floats. James realizes that cutting the block in half does not change its density. What type of property does James observe in his demonstration?
Intensive property James is observing an intensive property which is density. Density is intensive because it does not depend on the amount of substance present. James cut the block in half but the density did not change, this is because density is a ratio.
Which of the following observations about a basketball is NOT an example of an intensive property?
It has a mass of 600 grams The mass of the basketball would change if it were smaller, so it is an extensive property. The other examples would not change with changing size.
Choose the best explanation below for why dimensional analysis is also sometimes referred to as the factor label approach.
It is sometimes called the factor label approach because units are treated as a factor (along with a numeric factor) in a quantity like 25g, allowing us to subject the unit to algebraic operations as if they were variables. It is sometimes called the factor label approach because we can treat a quantity like 25g as a product of a numerical factor and a unit factor, allowing us to subject the unit to arithmetic operations as if they were variables. Dimensional analysis can be most helpful when helping to set up a problem involving multiplication or division, but it is not limited to multiplication and division: Adding or subtracting quantities, for example, requires they have the same unit, just like adding algebraic terms 5x and 6x, and this rule can be used to help set up or check a calculation.
Millikan utilized specific numerical data gathered by:
J.J. Thomson Millikan used J.J. Thomson's charge-to-mass ratio for the electron to determine the mass of the electron.
Which is an extensive property?
Length. The length of a substance does depend on the quantity present, the other examples do not.
The image below was captured over a hot mug of coffee on a cold morning. Which state(s) of matter are present in the image?
Liquid & Gas The image shows steam condensing as it hits the cool air. Pure steam, which is in gas phase, is completely invisible. The cloudy appearance comes from droplets of liquid water that form when the steam cools upon mixing with the cold air.
A 100 g sample of substance A is composed of 57.1 g of oxygen and 42.9 g of carbon. Another 100 g sample of substance B is made up of 72.7 g oxygen and 27.3 g carbon. What can be determined about substances A and B?
MR-A = 57.1/42.9 = 1.331 MR-B = 72.7/27.3 = 2.663 MR-B/MR-A = 2.663/1.331 ~=~ 2
Which of the following is an example of an extensive property? Density Color Odor Mass
Mass An extensive property is dependent on the amount of matter present. Mass is an extensive property
Which is an intensive property? Volume Melting point Weight Heat
Melting point Recall that an intensive property is a property of matter that is independent of the amount of substance in a sample. The melting point of a substance is an intensive property because it does not depend on the amount of substance present. Heat, volume, and weight are extensive properties because they depend on the amount of substance in a sample.
Which of the following statements is true about the relationship between atoms and molecules? Select all that apply.
Molecules are made of two or more atoms that are bonded together. Molecules may consist of one type of atom, or multiple types of atoms. Atoms are smaller units than molecules, since two or more atoms make a molecule. These chemically bonded atoms may be the same type (from the same element) or different types (different elements). Several pure elements exist in diatomic form, which is a molecule consisting of 2 atoms of the same element (for example, fluorine, or F2.
Which would you expect there to be more of, elements or compounds? Explain your answer.
More compounds is most likely since compounds are made by combining elements, so there are more possible combinations. There are only a little over a hundred elements, but these come together to form an unlimited number of possible compounds. It is true that nobody even knows how many compounds are present on the Earth, but that is partly because there are so many.
If a compound's formula mass was experimentally determined to be 76 amu, the chemical formula could be:
N2O3 The formula mass of N2O3 is calculated by 2(14.007)+3(15.999)=76.011 amu which is approximately 76 amu.
If a compound's formula mass was experimentally determined to be 71, the chemical formula could be:
NF3 Use the periodic table to get the atomic masses of each element. Then you can calculate the formula mass as such: N=14.007×1=14.007 F=18.998×3=56.994 Adding these together we get 71.001, which is approximately 71.
A molecule of dinitrogen tetroxide consists of 2 nitrogen atoms and 4 oxygen atoms. What is dinitrogen tetroxide's empirical formula?
NO2 The empirical formula must feature the simplest whole-number ratio of the constituent elements. The simplest form of the nitrogen: oxygen ratio, given as 2:4, is 1:2. Therefore, the empirical formula is NO2.
If a compound's formula mass is experimentally determined to be 40, the chemical formula could be:
NaOH Use the periodic table to get the atomic masses of each element. Then you can calculate the formula mass as such: H=1.008×1=1.008 Na=22.990×1=22.990 O=15.999×1=15.999 Adding these together we get 39.997, which is approximately 40.
Which of the following correctly describes the relationship between a nitrogen molecule and a nitrogen atom?
Nitrogen molecules are made of nitrogen atoms. Nitrogen molecules are made of two nitrogen atoms.
Which of the following events fail to follow the law of conservation of matter?
None of these All of these events follow the law of conservation of matter.
A strong magnet placed under a piece of paper makes a three-dimensional pattern in iron filings that are placed on top of the paper. This is an example of which of the following?
Physical Change. A physical change is a change in the state or properties of matter without any accompanying change in chemical composition. In the organization of the filings into a 3D form by the magnet, there is no chemical change. Also, none of the extensive or intensive properties of the magnet or filings change.
A strong magnet placed under a piece of paper makes a three-dimensional pattern in iron filings that are placed on top of the paper. This is an example of which of the following?
Physical change. A physical change is a change in the state or properties of matter without any accompanying change in chemical composition. In the organization of the filings into a three-dimensional form by the magnet, there is no chemical change. Also, none of the extensive or intensive properties of the magnet or filings change.
Whose experiment measured the charge of the electron, allowing the mass of the electron to also be determined when combined with earlier results on the charge to mass ratio of the electron?
Robert Millikan Robert Millikan discovered the charge of the electron in his oil drop experiment. Using the existing charge-to-mass ratio for the electron, he was able to then calculate the mass of the electron.
Which of the following is a rule for determining significant figures in calculations involving addition and subtraction?
Round the result to the same number of decimal places as the starting term with the lowest number of decimal places. The result should be rounded to the same number of decimal places as the starting term with the lowest number of decimal places.
0.738×0.28 is 0.20664 but is rounded to 0.21. Which rule or rules are applied to this calculation?
Round the result to the same number of significant figures as the value with the least number of significant figures. Round up if the digit to be dropped is 5 or greater. For multiplication and division, we round the result to the same number of significant figures as the value with the least number of significant figures. In this calculation, this means rounding to two significant figures by dropping all of the digits after and including the 6 in the thousandths place and rounding up to 0.21.
The ice and ocean in the image are both forms of H2O, in its solid and liquid states, respectively. This representation of water written as "H2O" aligns with which domain in chemistry?
Symbolic The representation of water using H2O is an aspect of the symbolic domain.
Which of the following is/are example(s) of an intensive property of a substance? Mass Temperature Color Volume
Temperature & Color If the property of a sample of matter does not depend on the amount of matter present, it is an intensive property.
Compare one mole of hydrogen gas with one mole of oxygen gas. They will have:
The same number of atoms and different masses. Consistent with its definition as an amount unit, 1 mole of any element contains the same number of atoms as 1 mole of any other element. However, the masses of 1 mole of different elements will differ since the masses of the individual atoms are drastically different.
Which of the following was Robert A. Millikan able to determine, either from his own work, or by building on the work of J. J. Thomson? Select all that apply.
The charge of an electron. The mass of an electron Millikan was able to measure the charge of individual electrons, and was also able to determine the mass by combining his result with Thomson's measurement of the charge to mass ratio of the electron.
convert from Celsius to Fahrenheit
The equation relating celsius and Fahrenheit is T∘F=(9/5×T∘C)+32.
There are two methods for determining the magnetic moment of a compound. Using the first method, a student produces a set of data with a standard deviation of 0.5μB. Using the second method, the student produces another set of data with a standard deviation of 0.02μB. Which of the following statements is true?
The first method is less precise than the second. The standard deviation from the first method is larger than the standard deviation from the second method, so the second method is more precise. No value is given for the true value, so no statements about the trueness of the measurements can be made.
In Ernest Rutherford's gold foil experiment, why did alpha particles sometimes (1 in 8,000) fly violently in a random direction?
The positive alpha particles were perfectly aligned to strike a nucleus Positively charged alpha particles typically pass right through, but if they are just perfectly aligned to strike a nucleus the huge repulsion between the positive charges makes them fly violently in a random direction.
The structural formula for a molecule is different from its molecular formula in that:
The structural formula shows how the atoms are connected. The structural formula for a molecule is different from its molecular formula in that the structural formula shows how the atoms are connected.
Elements are made of atoms that all have the same properties. How many individual atoms (all with the same properties) can a pure substance contain and still be considered an element?
There is no limit as to how many atoms an element can consist of. Elements are pure substances made of atoms that all have the same properties. A substance can contain any number of atoms and be considered an element, so long as every atom in the substance has the same properties and the substance can not be broken down by chemical changes.
Why are intensive properties used to characterize a particular substance?
They do not change as the amount of substance changes. Since intensive properties do not change with the amount of substance present, they are inherent to that substance and adequately describe that substance.
A thermometer reads 25∘C. If the temperature in the room is then increased by 16 K, what temperature will the thermometer read, in degrees Celsius?
Tk = Tc + 273.15 = 25 + 273.15 = 298.15 K Tktot = 298.15 + 16 = 314.15 K Tctot = Tktot - 273.15 = 314.15 - 273.15 = 41 C
The mass of a compound is taken 5 times with the following results: 26.6mg, 26.3mg, 26.2mg, 26.4mg, and 26.1mg. If the true mass is 25.6mg, what is the percent relative error for this set of data? Round to the nearest hundredth of a percent.
To find the percent relative error, first determine the mean of the data set. x¯= [26.6+26.3+26.2+26.4+26.1]/5 = 26.32 The percent relative error is given by the following formula. %e = |x¯−xtrue|/|xtrue| × 100% Substitute in the values to find the percent relative error. %e=|26.32−25.6|/|25.6|×100%=2.81% 2.81%
What is the formula mass in atomic mass units, for Al2(SO4)3?
Use the periodic table to get the atomic mass of each element. Multiply the atomic mass of the element by the number of atoms of that element in the compound. mass of Al: 26.982×2=53.964 mass of S: 32.066×3=96.198 mass of O: 15.999×4×3=191.988 Add the mass of each element to find the total. 53.964+96.198+191.988=342.15 amu Notice that subscripts in formulas (indicating numbers of atoms) are exact, so they do not constrain the number of significant figures.
How many moles of sulfur atoms are there in 64 g of S8?
We are asked to calculate the number of moles of sulfur atoms in 64g of S8. Use the molar mass of S8 to calculate the number of moles of S8 molecules. 64 (1/256.528) = 0.2495 mol Now, since there are 8 sulfur atoms for every molecule of S8, we will multiply the number of moles of S8 by 8 to calculate the moles of sulfur atoms. 0.2495 (8) = 1.995 mol S atoms Therefore, after rounding to two significant figures, we find that there are about 2.0mol of sulfur atoms in the sample.
Explain when trailing zeros should be considered significant.
When the number includes a decimal point. If the number has a decimal point, then all trailing zeros are significant. For example 3200., 320.0 and 0.03200 are all numbers that have two non-zero digits and two significant trailing zeros, for a total of four significant digits. If there is no decimal point, as in 3200, then the trailing zeros are considered either ambiguous or not-significant (opinions vary), but never considered to be significant.
Percent Error
[|x¯-xtrue| / |xtrue|] × 100%
Which of the following is NOT a substance made of one type of molecule.
a cell within the human body A cell is a collection of many different types of molecules.
A large change in temperature (not resulting from external heating) with the appearance of gas bubbles is most likely an indication of:
a chemical change A large change in temperature with the appearance of gas bubbles indicates that a chemical change has most likely occurred.
A compound can be split into elements by what kind of process?
a chemical process The only way to split a compound into elements is by a chemical process where chemical bonds break to give individual atoms.
Which of the following can be broken down into elements by chemical means?
a compound A compound can be broken down into its components by chemical means.
A pure substance that can be broken down by chemical changes is known as:
a compound A pure substance that can be broken down by chemical changes is known as a compound.
A molecule that is made up of more than one type of atom is known as
a compound Molecules containing more than one element are known as compounds. Elements and isotopes contain only one type of atom. Subatomic particles are the components that make up an atom.
Which of these is a part of the macroscopic domain of chemistry, as opposed the microscopic or symbolic domains?
a gust of wind A gust of wind, though comprised of tiny moving molecules, can be perceived by an individual in the natural world. Hydrogen atoms and bacteria can not be seen by the naked eye and are therefore microscopic. And finally, a graph is symbolic.
What is the result of two or more atoms forming chemical bonds with each other?
a molecule A molecule is formed as a result of two or more atoms forming chemical bonds with each other.
Which of the following terms describes the smallest particle of a substance that still retains the chemical properties of that substance? (Select all that apply.)
a molecule an atom Depending on whether the substance in question is an element or a compound, either an atom or a molecule is the smallest particle of that substance that retains its chemical properties. A substance cannot decompose into protons, neutrons and electrons without changing its very nature.
If something is a compound, it is also
a pure substance Pure substances are either elements or compounds. A compound is a pure substance composed of more than one element.
Which operation is performed to convert a temperature given in degrees Celsius to a temperature in kelvin?
add 273.15 Kelvin and Celsius have a linear relationship, but not a proportional relationship. They do not have the same starting point, but they increase at the same rate. 0 K is absolute zero, which is about −273.15∘C, so to get Kelvin from Celsius, add 273.15.
Molecules with similar properties might have the same:
all of the above All of these possibilities could lead to molecules having similar properties.
Which of the following states of matter can exert pressure?
all of the above All the phases of matter can exert pressure.
Chemical properties include the way a compound reacts with:
all of the above Any description of a compound's capacity to do a certain kind of chemistry would be characterized as a chemical property.
Which of the following is an example of a physical property?
all of the above Boiling point, metling point, and color are all considered physical properties.
Molecules that have the same structural formula will have the same:
all of the above If they have the same number of the same type of atoms, all of the above must be identical.
Which of the following represent the macroscopic domain in this image?
all of the above The moisture in the air, the icebergs, and the ocean are all part of the macroscopic domain.
Which of the following is a molecule?
all of the above Water, ozone, and glucose are all molecules, as they are all comprised of more than one atom.
Which of the following can only consist of only one kind of atom?
an element Elements consist of only one kind of atom. Compounds and mixtures consist of more than one type of atom. A pure substance is either an element or a compound, so it could consist of one type of atom, but it does not have to.
Which of the following are considered a pure substance? Select all that apply.
an element a compound An element and a compound are both considered to be pure substances. Elemental iron, for example, contains only iron atoms. Pure water, which is a compound, contains only water molecules, and nothing else.
What did Ernest Rutherford's work uncover?
an improved model of the atom Rutherford's work helped improve the model of the atom. He discovered that atoms consist of a small charged nucleus surrounded by tiny electrons, and are mostly empty space.
A mixture can be made up of two or more:
any of the above A mixture is made up of a combination of two or more pure substances, which could be elements, compounds, or both. A compound is also made up of two or more elements, but only in a specific ratio, while a mixture of two or more elements is not.
What is the smallest particle that an element can be divided into?
atom An atom is the smallest particle that an element can be divided into.
The smallest particle of an element that has the properties of that element is called a(n):
atom The atom is the smallest unit of an element. A proton and electron are subatomic, and a molecule is a combination of atoms.
The mass of an individual atom is most often described in:
atomic mass units (amu) The mass of an atom is most readily described in atomic mass units, because this unit was created specifically to discuss mass on the order of individual atoms. Grams and kilograms would require tedious scientific notation.
Choose the answer below that best completes this sentence: According to Dalton, compounds consist of different types of __________ in specific whole number ___________.
atoms, ratios Dalton showed that compounds are made up of fundamental units called atoms and that the atoms of each element in a compound are present in a fixed ratio.
Which of the following examples is considered a physical change? Select all that apply.
boiling water slicing potatoes into fries freezing juice to make ice pops Boiling water, slicing potatoes, and freezing juice are all examples of physical changes because these actions do not alter the chemical composition of the original substance. Conversely, when food is exposed to things like excessive air, temperature, moisture, light, or microorganisms, rotting (also known as decomposition) can occur. When this happens, the food is altered as it is chemically broken down into other, smaller substances. Because the chemical composition of the food changes, we consider this a chemical change.
Using a newer, or more sophisticated, measuring apparatus can increase:
both accuracy and precision For example, using a sophisticated digital balance instead of an old mechanical one enables us to take masses of objects that are both more accurate (closer to the true value) and precise (having more digits in them), largely because of how it reduces human error.
Sugar and water, with appropriate heat, can create caramel. In this example, sugar is undergoing a ___________.
chemical change Sugar and water, when forming caramel, are undergoing a chemical change as the product is different than the reactants.
Which of the following could be considered a physical change?
chopping firewood Chopping firewood simply breaks it into smaller pieces, it does not alter its chemical identity as the other options do. Grass growing seems like it could be a physical change, but it is actually the product of millions of chemical reactions on the cellular level.
Which of the following is a physical change? Select all that apply.
chopping wood bending metal cutting a cake Chopping wood, bending metal, and cutting a cake are all physical changes because the composition of the material isn't chemically changing. The changes that occur when frying an egg cannot be reversed and are therefore a chemical change.
Which of the following is NOT a physical property?
combustibility Combustibility is the measure of how readily something will burn in the presence of oxygen, which is a chemical reaction. Therefore combustibility is a chemical property.
A _______ is a substance with a fixed composition of atoms of two or more different elements that are bound together.
compound A compound is a substance with a fixed composition of atoms of two or more different elements that are bound together. For example, water is a substance composed of two different elements, hydrogen and oxygen, where there is a 2:1 ratio of hydrogen atoms to oxygen atoms. Therefore, water or H2O is a compound.
A molecule comprised of more than one type of atom is called a(n):
compound A mixture is composed of two or more types of matter and can be separated by physical changes. Elements are pure substances that cannot be broken down into simpler substances by chemical changes. And reactants are substances undergoing reaction.
The charges on the proton and electron are typically measured in:
coulombs These fundamental particles bear the fundamental unit of charge, which is either positive or negative 1.602×10^−19 coulombs.
A homogeneous mixture like salt and water can be separated by:
distillation A homogeneous mixture can be separated by physical means, such as causing one substance to boil away while the other remains, which is what distillation accomplishes.
A homogenous mixture varies from a heterogenous mixture in that a homogenous mixture has properties that:
do not vary in the mixture A homogenous mixture varies from a heterogenous mixture in that a homogenous mixture has a uniform composition.
Which particle contributes neither to the atomic number nor the mass number of an atom?
electron The electron does not have sufficient mass to be included in the mass number, and only the proton contributes to atomic number.
Suppose you have a drop of boiling water and a pot of boiling water. Even though the temperature is the same, the ramifications of spilling a drop versus dumping the whole pot on your skin are different.Heat is an example of an __________ property and temperature is an example of an __________ property.
extensive/intensive An intensive property is a property that does not depend on the amount of matter present. The temperature of the boiling drop and the temperature of the boiling water in the pot are the same; temperature does not depend on amount, so it is an intensive property. If dropped on your skin, a drop of boiling water would cause only minimal pain, while a pot of boiling water would cause burns or blisters. Thus, the heat transferred to the skin depends on the amount of boiling water, so it is an extensive property.
Moles
grams / molar mass
Molar mass
grams / mole
If object A and object B have the same density, but object A has greater mass, then object A must have:
greater volume If these objects have the same density, that means they have the same ratio of mass to volume, so a greater mass must also mean a greater volume.
Which sample has the greatest mass of hydrogen?
hese all have the same mass of hydrogen Since these all have the same number of hydrogen atoms, they will all contain the same mass of hydrogen.
Which element weighs, on average, approximately one atomic mass unit?
hydrogen Hydrogen, typically containing just one proton and one electron, will have an average mass of approximately one atomic mass unit.
Density is a(n):
intensive property Density is an intensive property, because a substance will have the same density no matter how much of it we are examining.
When a change in a physical property is observed,
it could be because of a physical change. An observed change to a physical property like phase, hardness, or density could be caused by a physical change like a phase transition or a heating. It cannot be both because a physical change is one that does not include any accompanying change in its chemical composition.
Which of the following is an example of an extensive property of a substance? Mass Temperature Length Volume
mass length volume Mass, volume, and length are extensive properties because they depend on the amount of a substance present in a sample. Temperature is an intensive property because it does not depend on the amount of substance. For example, imagine you have 1g of boiling water and 1kg of boiling water in identical containers. 1g of boiling water has the same temperature as 1kg of boiling water, but 1g of boiling water has less mass, less volume, and less depth (if we consider depth to be a length).
The observation that an atom has slightly less mass than the sum of the masses of its subatomic particles is called which of the following?
mass defect This observation, although it follows the conservation of energy, defies the conservation of matter, and is called the mass defect. For example, the nucleus of a helium atom is composed of two neutrons and two protons. The sum of the masses of two neutrons and two protons is 4.03298 amu, while the actual mass of a helium nucleus is found to be only 4.00260 amu. The difference (in this case, 0.03038 amu) is the mass defect for helium. The energy corresponding to the mass defect, using the equation E=mc^2, is referred to as the nuclear binding energy.
To find the number of neutrons in an atom, simply calculate:
mass number - atomic number The mass number gives the sum of the protons and neutrons, so if we subtract from that the atomic number, which is the number of protons, we will get the number of neutrons in an atom.
Grams
moles * molar mass
The characteristics of atoms are responsible for the following aspects of a type of matter, EXCEPT:
monetary value Monetary value is a man-made concept.
When considering precise mass, which particle has the greatest mass?
neutron The neutron has slightly more mass than the proton, and much more mass than the electron.
The nucleus of an atom can be split into smaller components by what kind of process?
none of the above The nucleus of an atom cannot be split into its components by either a physical or chemical change. Splitting an atom is a nuclear process.
We can always determine the precise structural formula from the:
none of the above We will not necessarily be able to determine the structural formula, even given all of the above data.
The mass number of an atom is equal to:
number of protons + number of neutrons The mass number of an atom is equal to the number of protons plus the number of neutrons found in the nucleus, each of which as an atomic mass of 1. For example, a typical carbon nucleus contains 6 protons and 6 neutrons and has a mass number of 12.
Which of the following is not a part of an atom?
photon An atom consists of protons, neutrons, and electrons.
When a pure substance undergoes a change from a solid state to a gaseous state, this is an example of a
physical change When a pure substance undergoes a change from a solid state to a gaseous state, this is an example of a physical change. This is because the chemical formula that describes a pure substance does not change during a change of state.
Which physical form(s) of matter have neither a definite volume nor definite shape?
plasma gas A physical form of matter that does not have a definite volume or shape is gas. Like a gas, plasma also lacks a definitive volume or shape.
Which of the following is a phase of matter? Select all that apply.
plasma solid liquid gas Plasma, solid, liquid, and gas are all phases of matter.
A measurement is ________ if it yields similar results when repeated.
precise A set of measurements are precise if they yield similar results as prior measurements.
What subatomic particle determines the element that an atom belongs to?
proton The number of protons in an atom determines its atomic number, which corresponds to a specific element.
______________ determine what element an atom belongs to, while ______________ allow atoms to do chemistry.
protons, electrons The number of protons determines an element's atomic number, while electrons participate in bonding to form molecules.
The digits in a measurement, including the uncertain last digit, are known as:
significant figures The digits in a measurement, including the uncertain last digit, are known as significant figures. Note that leading zeros are not included in the digits of a measurement, and are therefore not significant.
A homogeneous mixture is also known as a:
solution A homogeneous mixture is also known as a solution.
Which formula tells us the most about a molecule?
structural formula The structural formula tells us more than either the molecular formula or empirical formula, because a structural formula contains the information from a molecular and empirical formula in addition to showing the connections of atoms in the molecule.
Which of the following can be characterized as a physical change?
sweat evaporates from your skin Sweating is an example of a phase transition (from liquid to gas) which is a physical change. The rest of the options are examples of chemical changes.
Relative Standard Deviation
sx / |x¯| x¯ = mean sx = sqrt[(1/N-1)∑(Xi-X¯)^2]
Which of the following is NOT a physical property of a bronze medallion?
that it will slowly change color over many years The slow color change is due to chemistry that the material participates in over time, and is therefore not a physical property like the other options.
Which will have a greater mass of hydrogen, a 10.0 gram sample of water, or a 20.0 gram sample of water?
the 20.0 g sample Since any sample of water will have the same ratio of oxygen to hydrogen by mass, as a sample of water increases in mass, so will the masses of the individual elements. This must be true according to the law of definite proportions.
The prefix in subatomic tells us that subatomic particles are:
the basic building blocks of atoms The prefix "sub" can mean below, under, or imply that some smaller things are used to define a larger system. All of these contexts can apply here, to state that subatomic particles are less massive than atoms, take up less space than atoms, or more generally that they comprise atoms.
Which of the following is NOT a likely indicator of a chemical change?
the change in shape of a malleable metal The bending of a piece of metal, like a paper clip, is not a chemical change. Only when a new substance is formed, evidenced by a new material present or a change in color, can a chemical change be guaranteed.
The sum of the average atomic masses of all the atoms present in a substance's formula is known as:
the formula mass The sum of the average atomic masses of all the atoms present in a substance's formula is known as the formula mass.
A sample of an unknown substance contains 1.0 grams of copper and 0.558 grams of chlorine, while a different sample of that same substance contains 2.0 grams of copper and 1.116 grams of chlorine. Which law does this observation demonstrate?
the law of definite proportions That a particular substance has the same ratio of two elements by mass regardless of the sample size demonstrates the law of definite proportions, or the law of constant composition.
A 100 g sample comprised of molecule (A) is made up of 57.1 g of oxygen and 42.9 g of carbon. Another 100 g sample comprised of molecule (B) is made up of 72.7 g oxygen and 27.3 g carbon. The ratio of oxygen: carbon mass ratios between the two molecules is 2:1. Which law is demonstrated in this calculation?
the law of multiple proportions The law of multiple proportions states that when two elements react to form more than one compound, a fixed mass of one element will react with masses of the other element in a ratio of small, whole numbers.
What is exactly equal to the total number of protons and neutrons in an atom?
the mass number The number of protons and neutrons in an atom is equal to the atom's mass number. Atomic mass is the average mass of all the isotopes of a certain kind of atom.
What unit of measurement pertains to the number of microscopic molecules in a sample?
the mole The mole is the unit of measurement that allows for the unit conversion between atomic mass units (amu) and grams (g). The ability to convert units allows for us to calculate macroscopic amounts of matter, while at the same time respecting the stoichiometric ratios of a reaction.
Which of the following could be considered a microscopic observation about water?
the ratio of hydrogen to oxygen atoms in a water molecule Water's boiling point and transparency are macroscopic qualities, while its molecular formula is a symbolic representation. Only the number of atoms in the molecule is of microscopic concern.
A mole of one element contains _______ number of atoms as a mole of another element.
the same A mole of one element contains the same number of atoms as a mole of another element which is 6.022×10^23
If you boil a sample of water, the steam that results will have:
the same mass as the water The law of conservation of matter tells us that mass is conserved as matter changes forms. Therefore, all the water molecules in the steam will have the same mass as when they were in the liquid form.
Two molecules with the same structural formula must have:
the same type of atoms in precisely the same number The number and type of atoms must be identical for molecules with the same structural formula.
If we compare a mole of carbon atoms to a mole of oxygen atoms, which sample will contain more atoms?
they will contain the same number of atoms If they both contain a mole of atoms, they will both contain precisely avogadro's number of atoms.
What does 3CO2 mean?
three carbon dioxide molecules The molecule is CO2, and the 3 means that there are three of these molecules.
When computing using dimensional analysis:
unit conversions can be done either simultaneously or separately We can perform unit conversions one at a time or many at a time, just be sure to keep in mind that this could create a discrepancy in the number of significant figures in your result, depending on when you decide to round your value.
Volume
v = mass/density = m/d
Which is an example of a compound?
water Water is an example of a compound, as it is comprised of both hydrogen and oxygen.
Which of the following temperatures are equivalent to absolute zero (0 K)? Select all that apply.
−273.15∘C −459.67∘F −273.15∘C and −459.67∘F show absolute zero in the Celsius and Fahrenheit scales.
