Chapter 3 - Chemical Reactions & Reaction Stoichiometry, Chapter 2: Atoms, Molecules, and Ions, Chapter 1: Introduction: Matter, Energy, and Measurement
What are extensive properties
Extensive properties depend on the amount of the substance present. -Examples include mass, volume, or energy
What are the equations of conversion for Fahrenheit and celsius
F = 9/5(degree C)+32 C = 5/9 (degree -32)
Hydrocarbon Combustion Reactions
Hydrocarbons + O2 form CO2 & H2O. Major energy-producing process on Earth. Example- Propane
What does filtration do
In filtration, solid substances are separated from liquids and solutions.
what are inexact (measured) numbers?
Inexact (or measured) numbers depend on how they were determined. Scientific instruments have limitations (equipment errors) and individuals can read some instrumentation differently (human errors).
What are other types of properties
Intensive and extensive properties
Combustion Reaction
A rapid reaction that produces a flame, generally involving O2 from the air.
Write the balanced equation for the reaction that occurs when methanol, CH3OH (l), is burned in air.
2 CH3OH (l) + 3 O2 (g) --> 2 CO2 (g) + 4 H2O (g)
Percent Yield
(Actual Yield / Theoretical Yield) x 100%
(unbalanced) Na (s) + H2O (l) --> NaOH (aq) + H2 (g)
(balanced) 2 Na (s) + 2 H2O (l) --> 2 NaOH (aq) + H2 (g)
(unbalanced) CH4 + O2 --> CO2 + H20
(balanced) CH4 + 2 O2 --> CO2 + 2 H2O
Indicating Physical State
(g) gas (l) liquid (s) solid (aq) aqueous solution
What is a Calorie
- 1cal=4.184 J - This calorie is NOT the nutrition Calorie, which is kcal - 1 nutritional Calorie = 1 Cal= 1000 cal
What are significant figures?
-All digits of a measured quantity, including the uncertain ones, are called significant figures. -When rounding calculated numbers, we pay attention to significant figures so we do not overstate the accuracy of our answers.
What is density
-Density is a physical property of a substance. -It has units that are derived from the units for mass and volume.
What is the uncertainty in measurements
-Different measuring devices have different uses and different degrees of accuracy. -All measured numbers have some degree of inaccuracy. -The last digit measured is considered reliable, but NOT exact.
What are significant figure rules in calculations
-The least certain measurement limits the number of significant figures in the answer. -When addition or subtraction is performed, answers are rounded to the least significant decimal place. -When multiplication or division is performed, answers are rounded to the same number of digits as the measurement with the fewest number of significant figures. -Know the number of appropriate digits throughout, but round off at the end only!
How does conversion factors work
-We apply conversion factors (e.g., 1 in = 2.54 cm), which are equalities. -We can set up a ratio of comparison for the equality: 1 in./2.54 cm or 2.54 cm/1 in. -We use the ratio which allows us to change units (puts the units we have in the denominator to cancel). -We can use multiple conversions, as long as each one is an equality.
stoichiometric coefficients
-numbers placed in front of each compound -used to indicate the relative # of moles of a given species involved in the reaction
Ascorbic acid (vitamin C) contains 40.92% C, 4.58% H, and 54.50% O by mass. What is the empirical formula of ascorbic acid?
1) Assume 100g sample. - C = 49.92 g - H = 4.58 g - O = 54.50 g 2) Divide by molar mass. - C = (49.92g)/(12.01g/mol) = 3.407 mol - H = (4.58g)/(1.008g/mol) = 4.54 mol - O = (54.50g)/(16.00g/mol) = 3.406 mol 3) Calculate mole ratio, using smallest # of moles in sample - O. - C = (3.407) / (3.406) = 1.00 - H = (4.54) / (3.406) = 1.33 - O = (3.406) / (3.406) = 1.00 4) Multiple ratio by 3 to obtain whole numbers (as 1.33 = 1 1/3) Empirical Formula = C3H4O3
Dalton's Atomic Theory
1) elements are composed of atoms. 2) atoms of same element are identical, but differ from other elements. 3) atoms are neither created nor destroyed in chemical reactions; atoms of one element cannot be changed into atoms of a different element by chemical reactions 4) atoms only change when mixed with other elements
What are the rules of significant figures
1. All nonzero digits are significant. 2. Zeroes between nonzero digits are significant. 3. Zeroes at the beginning of a number are never significant. 4. Zeroes at the end of a number are significant if it contains a decimal point.
Mass spectrometer steps
1. Vaporisation (make gas) 2.Ionisation (remove electrons to make ions) 3.Acceleration (move ions toward negative grid) 4.Ion drift (ions deflected on curved path depending on mass - more mass = less deflection 5.Detection (can determine ions because they are separated by their mass)
How many elements are named?
118
12/6 C
12 = Mass Number (6 protons/6 neutrons) 6 = atomic number
If the object is 2 kg, and it moves at 1 m/s, it will posses 1 J of kinetic energy:
1J = ½ (2 kg) (1 m/s)2 OR: 1 J ≡ 1 kg · m2 /s2
What is the limiting reactant in producing H2O, given 10mol H2 and 7mol O2?
2 H2 + O2 --> 2 H2O H : O = 2 : 1 ratio If 10mol H2, need 5mol O2. --> 2mol O2 remaining Therefore, H2 is the limiting reactant as it gets entirely consumed.
Write a balanced equation for the combination reaction between lithium metal and fluorine gas.
2 Li (s) + F2 (g) --> 2 LiF (s) 1) All metals are solid at room temp - Li = (s) 2) Fluorine occurs as a diatomic molecule - F2 3) Metal + nonmetal = ionic solid = (s)
When 1.57 mol O2 reacts with H2 to form H2O, how many moles of H2 are consumed in the process?
2:1 ratio - 2 mol of H2O per 1 mol of O2 Therefore, 1.57 mol O2 x 2 = 3.14 mol H2O 1:1 ratio - 2 mol of H2O per 2 mol of H2 Therefore, 3.14 mol H2O = 3.14 mol H2
Naturally occurring chlorine is 75.78% chlorine - 35 (atomic mass 34.969) and 24.22% chlorine - 37 (atomic mass - 36.966 amu). Calculate the atomic weight of chlorine.
35.45 amu
Avogadro's Number
6.022 x 10^23 = one mole.
electron mass
9.11 x 10^-31 kg
molecular formula
A chemical formula that shows the actual number and kinds of atoms in a molecule, but not the arrangement of the atoms.
alpha particle
A cluster of 2 protons and 2 neutrons emitted from a nucleus in one type of radioactivity bent by an electric field positive charge large, stopped by paper 2+ charge Mass of about 7400 times that of an electron
Oxidation Reaction
A combustion reaction that occurs at body temperature over a series of intermediate steps.
What is a compound?
A compound is a substance which can be decomposed to simpler substances because it is made up of more than one element
What is a compound made of?
A compound is made of atoms from two or more different elements
What is an example of a chemical change?
A copper penny reacts with nitric acid; it gives a blue solution of copper (II) nitrate and a brown gas called nitrogen dioxide
gamma particle
A form of radiation; it's a type of electromagnetic radiation at a high frequency. not bent by electric field no particles; no charge similar to X rays
Law of Constant Composition
A given compound always contains elements in exactly the same proportion by mass (based on 4)
periods on periodic table
A horizontal row of elements in the periodic table
Limiting Reactant
A reactant that is totally consumed during a chemical reaction, limits the extent of the reaction, and determines the amount of product.
Angstrom
A unit of length equal to one ten-thousandth 10^-10 of a meter. Used to measure atoms
What is accuracy?
Accuracy refers to how closely individual measurements agree with the correct, or "true," value (accepted value).
What is an element
An element is a substance which can not be decomposed to simpler substances
What are atoms
Atoms are the building blocks of matter and is the smallest unit of matter
Isotopes
Atoms of the same element that have different numbers of neutrons; all alike chemically - behave similarly
Write a balanced equation for the decomposition reaction that occurs when solid barium carbonate is heated.
BaCO3 (s) --> BaO (s) + CO2 (g) 1) Many metals decompose to metal oxides + carbon dioxide when heated
Why are empirical formulas used?
Because you cannot always determine the exact components of a compound when analyzing substances
Calculate the formula weight of sucrose, C12H22O11
C = (12.0 amu) x 12 = 144.0 amu H = (1.0 amu) x 22 = 22.0 amu O = (16.0 amu) x 11) = 176.0 amu == 342.0 amu
Calculate the percentage of carbon, hydrogen, and oxygen (by mass) in C12H22O11.
C = (12.0 amu) x 12 = 144.0 amu H = (1.0 amu) x 22 = 22.0 amu O = (16.0 amu) x 11) = 176.0 amu == 342.0 amu C = (144.0/342.0) * 100% = 42.1% H = (22.0/342.0) * 100% = 6.4% O = (176.0/342.0) * 100% = 51.5%
What is the molar mass of glucose, C6H12O6?
C = (12.0g/mol) x 6 = 72.0 g/mol H = (1.0g/mol) x 12 = 12.0 g/mol O = (16.0g/mol) x 6 = 96.0 g/mol == 180 g/mol
Determine the Molecular Formula given the Empirical Formula for Ascorbic Acid (C3H4O3), molecular weight = 176 amu
C3H4O3 Empirical FW = C (12.01) x 3 = 36.03 amu H (1.008) x 4 = 4.032 amu O (16.00) x 3 = 48 amu == 88.0 amu Molecular Weight / Empirical FW = (176 amu) / (88 amu) = 2 So, multiply subscripts by 2 to determine molecular formula. = C6H8O6
Calculate the mass, in grams, of 0.433 mol of calcium nitrate, Ca(NO3)2.
Ca = (40.1 g/mol) N = (14.0 g/mol) x 2 = 28 g/mol O = (16.0 g/mol) x 6 = 96.0 g/mol == 164.1 g/mol Ca(NO3)2 Sample = 0.433 mol Mass (g) = (0.433 mol) x (164.1g/mol) == 71.1 g Ca(NO3)2
What units are temperature measuremented
Celsius and Kelvin
What are chemical properties?
Chemical properties can only be observed when a substance is changed into another substance. -One common chemical property is flammability, or the ability to burn in oxygen
What is chemistry?
Chemistry is the study of matter, its properties, and the changes it undergoes. It is central to our fundamental understanding of many science-related fields.
What is the law of constant composition (or the law of definite proportions)?
Compounds have a definite composition. That means that the relative number of atoms of each element in the compound is the same in any sample.
Halogens
Contains nonmetals, 7 valence electrons in it's outermost energy level. Very reactive
What is an example of physical change?
Converting between the three states of matter is a physical change
What is the formula for density?
D=m/v
What is dimensional analysis used for?
Dimensional analysis is used to change units.
What is distillation
Distillation uses differences in the boiling points of substances to separate a homogeneous mixture into its components.
distillation
Distillation uses differences in the boiling points of substances to separate a homogeneous mixture into its components.
What are elements made of?
Each element is made of a unique kind of atom, but can be made of more than one atom of the kind.
What is Coulomb's Law?
Eel = kQ1Q2/ d
Which subatomic particle was discovered 1st? Last?
Electron 1st (cathode ray experiments) Neutron last
noble gases
Elements in group 8A of the periodic table. Have no charge and are gases under normal conditions. (Helium, Neon, Argon, Krypton, Xenon, Radon) odorless, not reactions because they have 8 valence electrons
metallic elements
Elements that are usually solids at room temperature, exhibit high electrical and heat conductivity, and appear lustrous. Most of the elements in the periodic table are metals. all elements on left and middle (except hydrogen)
Metalloids
Elements that may accept or donate electrons readily and possess a mixture of metallic and nonmetallic properties B, Si, As, Te, Ge, Sb
What is energy
Energy is the capacity to do work or transfer heat
Balanced Chemical Equation
Equal number of atoms of each element on either side of the arrow. Atoms are neither created nor destroyed in a reaction.
What are exact numbers
Exact numbers are counted or given by definition. For example, there are 12 eggs in 1 dozen.
Ionic Solid
Formed by a combination reaction between a metal and a non-metal.
alkali metals
Group 1, 1 electron in outer level, very reactive, soft, silver, shiny, low density; Lithium, Sodium, Potassium, Rubidium, Cesium, Francium
Chalcogens
Group 6A O, S, Se, Te, Po
diatomic elements
H2, N2, O2, F2, Cl2, Br2, I2 usually occur as diatomic molecules
What are intensive properties
Intensive properties are independent of the amount of the substance that is present. -Examples include density, boiling point, or color -these are important for identifying a substance
Plum Pudding Model
J.J Thomsons model of an atom, in which he thought electrons were randomly distributed within a positively charged cloud
What is the unit of energy
Joule (J) it is derived unit of KE = 1/2m v2
When carbon and oxygen react, two different compounds can form depending on the conditions. Compound A contains 1.333 g of oxygen per gram of carbon, whereas compound B contains 2.666 g of oxygen per gram of carbon. Does this observation illustrate the law of conservation of mass or the law of multiple proportions? If compound A has an equal number of oxygen and carbon atoms, what can we conclude about the composition of compound B?
Law of multiple proportions second compound has two oxygen atoms for each carbon
What is length
Length is a measure of distance. The meter is the base unit
Combination Reaction Example
Magnesium + Oxygen --> Magnesium Oxide 2 Mg (s) + O2 (g) --> 2 MgO (s)
What is mass?
Mass is a measure of the amount of material in an object. SI uses the kilogram as the base unit. The metric system uses the gram as the base unit.
Which two of these elements would you expect to show the greatest similarity in chemical and physical properties? B, Ca, F, He, Mg, P
Mg and Ca both alkaline earth metals
How many atoms of Mg, O, and H are represented by the notation 3Mg(OH)2?
Mg: 3 O: 6 H: 6
How can mixtures be separated
Mixtures can be separated based on physical properties of the components of the mixture.
What are mixtures made of
Mixtures can vary in composition throughout a sample (heterogeneous) or can have the same composition throughout the sample (homogeneous)
What properties does a mixture exhibit
Mixtures exhibit the properties of the substances that make them.
What are molecules made of
Molecules are made of more than one compound
When Na and S undergo a combination reaction, what is the chemical formula of the product?
Na2 + S --> Na2S Sodium Sulfide
Cathode
Negative electrode
What are the only five elements make up 90% of the Earth's crust by mass?
Oxygen 49.5% Silicon 25.7% Calcium 3.4% Iron 4.7% Aluminum 7.5% Other 9.2%
What are physical changes
Physical changes are changes in matter that do not change the composition of a substance -Examples include changes of state, temperature, and volume.
What helps us SEE that chemical change has occurred?
Physical properties
What are physical properties?
Physical properties can be observed without changing a substance into another substance. - Some examples include color, odor, density, melting point, boiling point, and hardness.
Anode
Positive electrode
Decomposition Reaction Example
Potassium Chlorate --> Potassium Chloride + Oxygen 2 KClO3 (s) --> 2 KCl (s) + 3 O2 (g)
What is potential energy
Potential energy of an object depends on its relative position compared to other objects. - PE= mgh
What is precision?
Precision is a measure of how closely individual measurements agree with one another.
Combustion Reaction Example
Propane Combustion C3H8 (g) + 5 O2 (g) --> 3 CO2 (g) + 4 H2O (g)
atomic weight
Protons and neutrons Average of the mass numbers of all isotopes Mass of isotopes added then multiplied by relative abundance
Calculate the number of moles of glucose (C6H12O6) in a 5.380 g sample.
Sample = 5.380 g Molar Mass of Glucose = 180 g/mol # moles = (5.380 g) / (180 g/mol) == 0.029 mol C6H12O6
What is the difference between scientific theory and scientific law?
Scientific theory explains why phenomena occur. Scientific Law describes what phenomena happen. They both repeated successful predictions
atomic weight equation
Sigma(isotope mass x fractional isotope abundance)
Reactant
Starting substance in a chemical reaction.
Product
Substance produced in a chemical reaction.
What is temperature
Temperature is considered the "hotness and coldness" of an object that determines the direction of heat flow. -Heat flows spontaneously from an object with a higher temperature to an object with a lower temperature
Mole
The amount of matter that contains as many objects (atoms, molecules, or whatever other objects we are considering) as the number of atoms in exactly 12 g of isotopically pure Carbon-12. OR, Avogadro's number.
Actual Yield
The amount of product actually obtained when all of a limiting reactant is consumed. It is almost always less than (never greater than) the theoretical yield. -Some of the reactants may not react, or may react differently.
Stoichiometry
The area of study that examines the quantities of substances consumed and produced in chemical reactions.
What changes when balancing a chemical equation?
The coefficient. NOT the subscript.
What does SI units mean?
The international system of units
What is Kelvin based on
The kelvin is the SI unit of temperature -it is based on the properties of gases -there are no negative Kelvin temperatures -the lowest possible temperature is call absolute zero (0 K) - K= Degree C +273.15
Molar Mass
The mass (in grams) of one mole of a substance. The atomic weight of an element (amu) is numerically equal to the mass (gram) of 1 mol of that element. Example: Cl = 35.5 amu = 1 mol Cl = 35.5g
What is the most common units in density
The most common units are g/mL or g/cm3
Percentage Composition
The percentage by mass of each element in a compound.
Radioactivity
The process in which some substances spontaneously emit radiation
Theoretical Yield
The quantity of product calculated to form when all of a limiting reactant is consumed.
Formula Weight (FW) / Molecular Weight (MW)
The sum of the atomic weight (AW) of atoms in the chemical formula of a substance. Example: FW of H2SO4 = 2 (1.0 amu (H)) + (32.1 amu (S)) + 4 (16.0 amu (O)) FW = 98.1 amu
what happens in chromatography
This technique separates substances on the basis of differences in the ability of substances to adhere to the solid surface, in this case, dyes to paper.
What is work
Work is the energy transferred when a force exerted on an object causes a displacement of that object
Aspirin is composed of 60.0% carbon, 4.5% hydrogen, and 35.5% oxygen by mass, regardless of its source. Use the flow chart to classify aspirin
compound
empirical formula
a chemical formula showing the ratio of elements in a compound rather than the total number of atoms H2O2 becomes HO No formula can be only empirical; can be molecular or molecular and/or empirical cannot determine molecular formula from empirical formal without more information
molecular compound
a compound that is composed of molecules contain more than one type of atom usually non-metals
structural formula
a formula that shows the arrangement of atoms in the molecule of a compound. Cannot determine bond angles from structural formula
diatomic molecule
a molecule containing only two atoms
beta particles
a negatively charged particle (an electron) emitted from the nucleus of an atom during radioactive decay. bent by an electric field radioactive equivalent of a cathode ray 1- charge
Decomposition Reaction
a reaction in which a single compound breaks down to form two or more simpler substances
ball-and-stick molecular model
a representation of the arrangement of atoms in a molecule that shows how the atoms are bonded to each other and the overall shape of the molecule accurately represents angles
cathode ray
a stream of electrons produced at the negative electrode (cathode) of a tube containing a gas at low pressure radiation the was deflected by negative electric or magnetic fields; made of negative particles we now call electrons
What is a substance
a substance has distinct properties and a composition that does not vary from sample to sample
atomic mass unit (amu)
a unit of mass equal to one-twelfth the mass of a carbon-12 atom Used for mass of atom 1 amu = 1.66054 x 10^-24 g
groups on periodic table
a vertical row of elements in the periodic table
Magnesium has three isotopes with mass numbers 24, 25 and 26. a. Write the complete chemical symbol for each. b. How many neutrons are in an atom of each isotope?
a. 24/12 Mg, 25/12 Mg, 26/12 Mg b. 12, 13, 14
Write the empirical formula for a. glucose, C6H12O6, b. N2O
a. CH2O b. same
How many proton, neutrons and electrons are in an atom of a. 197 - Au b. strontium-90
a. P = 79, N = 118, E = 79 b. P = 38, N = 52, E = 38
Three types of radiation
alpha, beta, gamma
mass spectrometry
an experimental method of determining the precise mass and relative abundance of isotopes in a given sample using an instrument called a mass spectrometer identify chemical compounds and identify solutions separates ions according to mass by changing to strength of the magnetic field or the accelerating voltage ions of various masses can be selected to enter the detector
Space-filling models
atoms fill the space between each other to more closely represent our best idea for how a molecule might appear if we could scale it to a visible size
What are pure substances called
atoms of an element, molecules of an element, molecules of a compound
How to determine which isotope is the most common?
compare atomic weight with isotope amu/which ever is the most similar to average atomic weight is the most common
Nuclear Model of the Atom
created by Ernest Rutherford. Replaced the Plum Pudding Model. Atom is like a miniature solar system with the positive particles in the middle and the negative particles orbiting as the planets do around the center.
What are two types of substances
elements and compounds
cathode ray tube
evacuated glass tube in which a stream of electrons emitted by a cathode strikes a fluorescent material, causing it to glow when high voltage was applied to electrodes in the tube, radiation was produced between the electrodes. The radiation originated at the negative electrode and traveled to the positive electrode. Cathode rays could be detected because they cause other materials to off light
Which scale is not used in scientific measurements
fahrenheit
What are some methods used to separate mixtures?
filtration, distillation, and chromatography
what is force
force is any push or pull on an object
What glassware used for measuring volume
graduated cylinder, syringe, burette, pipette, and volumetric flask
What are examples used in the metric system
gram, meter, second, celsius, kelvins, mole, centimeter, liter
Mass Spectrum Graph
graph of intensity of the detector signal versus ion atomic mass graph shows atomic mass and signal intensity or the relative abundance of the ions
What is heat
heat is the energy used to caused the temperature of an object to increase
What are the only three elements 90% of the human body by mass?
hydrogen, calcium, and oxygen
Would you expect the number of alpha particles scattered at large angles in Rutherford's experiment to increase, decrease or stay the same as the thickness of the gold foil increases?
increase higher probability of alpha particle hitting a nucleus and being deflected
What is celsius scale based on
it is based on properties of water. -0 degrees celsius is the freezing point of water -100 degrees celsius is the boiling point of water
What is commonly used for chemical change
kJ
What are the two fundamental forms of energy
kinetic and potential energy
What is kinetic energy
kinetic energy is the energy of motion. -Its magnitude depends on the object's mass and its velocity - KE= 1/2mv^2
What are the most commonly used metric units for volume
liter and milliliter
What is matter
matter is anything that has mass and takes up space
alkaline earth metals
metallic elements in group 2 of the periodic table which are harder than the alkali metals and are also less reactive
What are examples of units?
meter, kilogram, kelvin, second, mole, ampere, candad
Which subatomic particle has the largest mass?
neutron (neutron and proton similar in size)
atomic mass unit
one twelfth the mass of a carbon-12 atom
What are the two types of properties
physical and chemical
What are the types of changes
physical and chemical changes
What are chemical changes
result in new substances -Examples include combustion, oxidation, and decomposition.
periodic table staircase
separates metals from non-metals from B to At Metalloids on line
Perspective drawings
show crude the three-dimensional array of atoms in a compound
What are the three states of matter and examples of each
solid- ice liquid- liquid water gas- water vapor
What is a homogeneous mixture called
solution
What is the two methods of classification
state of matter and composition of matter
How do chemists represent elements?
symbols
What are symbols
symbols are one or two letters. the first is always capitalized. Some elements are based on latin, greek, or other foreign language names
Law of Conservation of Mass
the law that states that mass cannot be created or destroyed in ordinary chemical and physical changes; total mass of materials present after a chemical reaction is the same as the total mass present before the reaction
Which part of the atom has high density?
the nucleus
atomic number
the number of protons in the nucleus of an atom
Molecular form
two or more of the same type of atom bound together usually non-metals
Combination Reaction
two or more substances react to form one product
What are concepts of numbers in science
units of measurement, quantities that are measured and calculated, uncertainty in measurement, significant figures, and dimensional analysis
How to solve for relative abundance of an isotope?
use elimination method pick one of the isotopes amu and minus it from each part of equation. Allows you to solve for one isotope https://video.search.yahoo.com/yhs/search?fr=yhs-iba-1&hsimp=yhs-1&hspart=iba&p=how+to+calculate+relative+abundance+of+isotopes#id=1&vid=3934d62821b6536b4c99c2d16f6e4b16&action=click
Volume of an atom
volume of the space occupied by the electrons of an atom
Law of Multiple Proportions
whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers