Chemistry Answers
Consider the numbers 23.68, and 4.12. The sum of these numbers has ___ significant figures, and the product of these numbers has ___ significant figures.
4, 3
Which of the following diagrams best illustrates how a displacement in an ionic crystal results in cleavage and brittleness?
Before Displacement After Displacement
Which of the following is a nonpolar molecule that contains polar bonds?
CO2
Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits each statement. A choice may be used once, more than once, or not at all in each set. The following questions refer to the reactions represented below. (A) H2SeO4(aq) + 2 Cl-(aq) + 2 H+(aq) → H2SeO3(aq) + Cl2(g) + H2O(l)(B) S8(s) + 8 O2(g) → 8 SO2(g)(C) 3 Br2(aq) + 6 OH-(aq) → 5 Br-(aq) + BrO3-(aq) + 3 H2O(l)(D) Ca2+(aq) + SO42-(aq) → CaSO4(s)(E) PtCl4(s) + 2 Cl-(aq) → PtCl62-(aq) A precipitation reaction
Ca2+(aq) + SO42-(aq) → CaSO4(s)
Which of the following lists Mg, P, and Cl in order of increasing atomic radius?
Cl < P < Mg
Two pure elements react to form a compound. One element is an alkali metal, XX, and the other element is a halogen, ZZ. Which of the following is the most valid scientific claim that can be made about the compound?
It contains ionic bonds.
The mass spectrum of element X is presented in the diagram above. Based on the spectrum, which of the following can be concluded about element X?
The atomic mass of X is between 90 and 92.
At standard temperature and pressure, a 0.50 mol sample of H2 gas and a separate 1.0 mol sample of O2 gas have the same
average molecular kinetic energy
For spring break you and some friends plan a road trip to a sunny destination that is 2105 miles away. If you drive a car that gets 33 miles per galloon and gas costs $3.199/gal, about how much will it cost to get to your destination?
$200
The particle-level diagram above represents the structure of solid KF. Although the molar mass of KCl is greater than that of KF, the density of KCl is actually less than that of KF. Which of the following representations of the structure of KCl best helps to explain this phenomenon?
+-+ -+- The - is larger +-+
If 50. mL of 1.0 M NaOH is diluted with distilled water to a volume of 2.0 L, the concentration of the resulting solution is
0.025 M
A scientist obtains the number 0.045006700 on a calculator. If this number actually has four significant figures, how should it be written
0.04501
You measure water in two containers: a 10-mL graduated cylinder with marks at every mL, and a 1-mL, pipet marked at every 0.1 mL. If you have some water in each of the containers and add them together to what decimal place could report the total volume of water?
0.1 mL
What is the subscript of barium in the formula barium sulfate
1 (BaSO4)
How many mL of 10.0 M HCl are needed to prepare 500. mL of 2.00 M HCl ?
100. mL
Which of the following represents the ground state electron configuration for the Mn3+ ion? (Atomic number Mn = 25)
1s2 2s22p63s23p63d4
Al(s)→Al3+(aq)+3e− Zn2+(aq)+2e−→Zn(s) The half-reactions for the oxidation-reduction reaction between Al(s)Al(s) and Zn2+(aq)Zn2+(aq) are represented above. Based on the half-reactions, what is the coefficient for Al(s)Al(s) if the equation for the oxidation-reduction reaction is balanced with the smallest whole-number coefficients?
2
The diagram above represents H2(g) and N2(g) in a closed container. Which of the following diagrams would represent the results if the reaction shown below were to proceed as far as possible? N2(g) + 3 H2(g) → 2 NH3(g)
2 NH3 ions and 2N2 ions
The distance of 21 km equals
2.1 x 10^4 m
Based on periodic trends and the data in the table above, which of the following are the most probable values of the atomic radius and the first ionization energy for potassium, respectively?
242 pm, 419 kJ/mol
Ni(s)→Ni2+(aq)+2e− Ag+(aq)+e−→Ag(s) Which of the following is the balanced net ionic equation for an oxidation-reduction reaction between Ag+(aq)Ag+(aq) and Ni(s)Ni(s) based on the half-reactions represented above?
2Ag+(aq)+Ni(s)→2Ag(s)+Ni2+(aq)
Express then number 0.000333 in scientific notation
3.33 x 10^-4
Using the rules of significant figures, calculate the following: 4.0021 - 0.179
3.823
A firefighter carrying a cargo of uranium hexafluoride sank in the English Channel in late August 1984. The cargo of uranium hexafluoride weighed 2.253 x 10^8 kg and was contained in 30 drums, each containing 1.47 x 10^6 L of UF6. What is the density (g/mL) of uranium hexafluoride
5.11 g/mL
Under which of the following conditions of temperature and pressure will H2 gas be expected to behave most like an ideal gas?
500 K and 0.10 atm
Which of the following particulate diagrams best shows the formation of water vapor from hydrogen gas and oxygen gas in a rigid container at 125oC?
6H2, 3O2 -> 6H2O
How many significant figures are there in the number 0.04560700
7
A piece of zinc with a mass of 12.14 g is submerged in 46.3 cm^3 of water in a graduated cylinder. The water level increases to 48.0 cm^3. The correct value for the density of zinc from these data is
7.1 g/cm^3
A sample of CaCO3 (molar mass 100. g) was reported as being 30. percent Ca. Assuming no calcium was present in any impurities, the percent of CaCO3 in the sample is
75%
8.1 kilogram(s) contains this many grams.
8.1 x 10^3
Which of the following molecules contains exactly three sigma (σ) bonds and two pi (π) bonds?
C2H2
A gas mixture at 0°C and 1.0atm1.0atm contains 0.010mol of H2, 0.015mol of O2O2, and 0.025 mol of N2. Assuming ideal behavior, what is the partial pressure of hydrogen gas (H2) in the mixture?
About 0.20atm, because H2 comprises 20% of the total number of moles of gas.
A student mixes 20.0 kg of white KCL crystals with distilled water in a beaker. After the mixture was stirred, no crystals are visible and the solution is clear. After several days, all of the water evaporates and white crystals are found in the beaker. Which of following pieces of experimental evidence would best help the student to confirm that a new compound had not been made and that only a physical change occurred?
After the water has evaporated, the white crystals in the beaker have a mass of 20.0 g.
The diagrams above represent solutes present in two different dilute aqueous solutions before they were mixed. Water molecules are not shown. When the solutions were combined, a precipitation reaction took place. Which of the diagrams below is the best particle representation of the mixture after the precipitation reaction occurred?
Answer D Correct. Salts of group 1 metals are always soluble. Therefore, the sodium ion will always remain in solution. The same is true for salts containing NO−3NO3− ions. The only possible combination leading to the formation of a precipitate is Ag+(aq)+Cl−(aq)→AgCl(s)Ag+(aq)+Cl−(aq)→AgCl(s). AgCl on the bottom
Steel is an alloy consisting of Fe with a small amount of C. Elemental Cr can be added to steel to make the steel less likely to rust; Cr atoms react with oxygen in the air to form a nonreactive layer of chromium oxide on the surface of the steel, preventing the oxidation of underlying Fe atoms. A sample of steel-chromium alloy contains 15 percent Cr by mass. Which of the following diagrams best shows a particle-level view of a surface section and an interior section of the alloy represented below at the left? (The atomic radii of the atoms involved are given in the table below at the right.)
B The figure presents a particle diagram consisting of 12 large unshaded circles, which represent Fe atoms and 6 small shaded circles, which represent C atoms. The large Fe atoms are arranged in a 3 by 4 array. The small C atoms are located throughout this lattice, at every intersection of four large Fe atoms.
Atoms of Mg combine with atoms of F to form a compound. Atoms of which of the following elements combine with atoms of F in the same ratio?
Ba
Which of the following pairs is incorrect?
BaPO4, barium phosphate
The table above shows the structural formulas and molar masses for three different compounds. Which of the following is a list of the compounds in order of increasing boiling points?
Butane < acetone < 1-propanol
In which of the following processes are covalent bonds broken?
C(diamond) → C(g)
Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits the statement. A choice may be used once, more than once, or not at all. The following questions refer to the chemical reactions represented below. (A) 2 C6H6(l) + 15 O2(g) → 12 CO2(g) + 6 H2O(l) (B) C2H3O2-(aq) + H3O+(aq) → HC2H3O2(aq) + H2O(l) (C) 4 H+(aq) + 4 Co2+(aq) + O2(g) + 24 NH3(aq) → 4 Co(NH3)63+(aq) + 2 H2O(l) (D) CaCO3(s) → CaO(s) + CO2(g) (E) 2 H2O2(l) → O2(g) + 2 H2O(l) The reaction between a Brønsted-Lowry acid and a Brønsted-Lowry base
C2H3O2-(aq) + H3O+(aq) → HC2H3O2(aq) + H2O(l)
Which of the following molecules contains only single bonds?
C2H6
C2H6 - 30 C4H10 - 58 The molecular formula and molar mass of two straight-chain hydrocarbons are listed in the table above. Based on the information in the table, which compound has the higher boiling point, and why is that compound's boiling point higher?
C4H10 , because it has more electrons, resulting in greater polarizability and stronger dispersion forces
Which of the following molecules is least soluble in water?
CCl4
Which of the following molecules is nonpolar but has polar covalent bonds?
CCl4
______ are substances with constant composition that can be broken down into elements by chemical processes
Compounds
Which of the following statements is false?
Compounds can exist as atoms or molecules
Thymine and adenine form a base pair in the DNA molecule. These two bases can form a connection between two strands of DNA via two hydrogen bonds. Which of the following diagrams shows the correct representation of the hydrogen bonding (denoted by dashed lines) between thymine and adenine base pairs?
D, https://assets.learnosity.com/organisations/537/media.academicmerit.com/ebfe77193df029f9cd473abc360c1d71/original.png
The particle diagram above represents an aqueous solution of a weak monoprotic acid. The white circles represent HH atoms. Which of the following shows the species that act as a Brønsted-Lowry base and its conjugate acid, in that order, in the solution?
D. Black circle with two white dots and black circle with three white dots
Which of the following arranges the molecules N2, O2, and F2 in order of their bond enthalpies, from least to greatest?
F2 < O2 < N2
Which of the following statements concerning these figures is correct?
Figure I represents random error and figure II represents systematic error.
Which of the following figure(s) represent a result having high precision?
Figure II and Figure III
Which of the following is the net ionic equation for the reaction between aqueous sodium fluoride and hydrochloric acid?
F−(aq)+H+(aq)→HF(aq)
Consider atoms of the following elements. Assume that the atoms are in the ground state. The atom that contains only one electron in the highest occupied energy sublevel
Ga
Which of the following represents a pair of isotopes? Atomic Number | Mass Number
I. 7 | 13 II. 7 | 14
All of the following are in aqueous solution. Which is incorrectly named?
HBr, bromic acid
A 0.5 mol sample of He(g) and a 0.5 mol sample of Ne(g) are placed separately in two 10.0 L rigid containers at 25°C. Each container has a pinhole opening. Which of the gases, He(g) or Ne(g), will escape faster through the pinhole and why?
He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms.
When hafnium metal is heated in an atmosphere of chlorine gas, the product of the reaction is found to contain 62.2 percent Hf by mass and 37.4 percent Cl by mass. What is the empirical formula for this compound?
HfCl3
The graph above shows the speed distribution of molecules in a sample of a gas at a certain temperature. Which of the following graphs shows the speed distribution of the same molecules at a lower temperature (as a dashed curve) ?
Higher Peak, less speed
Which of the following describes the changes in forces of attraction that occur as H2O changes phase from a liquid to a vapor?
Hydrogen bonds between H2O molecules are broken.
The elements I and Te have similar average atomic masses. A sample that was believed to be a mixture of I and Te was run through a mass spectrometer, resulting in the data above. All of the following statements are true. Which one would be the best basis for concluding that the sample was pure Te?
I consists of only one naturally occurring isotope with 74 neutrons, whereas Te has more than one isotope.
Which of the following correctly indicates whether the solid represented by the particulate model shown above conducts electricity and explains why or why not?
It does not conduct electricity because its ions cannot move freely within the solid.
A compound contains 1.10 mol of K, 0.55 mol of Te, and 1.65 mol of O. What is the simplest formula of this compound?
K2TeO3
In solid methane, the forces between neighboring CH4 molecules are best characterized as
London (dispersion) forces
1s2 2s2 2p6 3s2 3p3 Atoms of an element, X, have the electronic configuration shown above. The compound most likely formed with magnesium, Mg, is
Mg3X2
According to the information in the table above, a 1.00 g sample of which of the following contains the greatest mass of oxygen? Compound Molar Mass(grams) Na2O 62.0 MgO 40.3 K2O 94.2 CaO 56.1
MgO
A 0.10 M aqueous solution of sodium sulfate, Na2SO4 , is a better conductor of electricity than a 0.10 M aqueous solution of sodium chloride, NaCl. Which of the following best explains this observation?
More moles of ions are present in a given volume of 0.10 M Na2SO4 than in the same volume of 0.10 M NaCl.
Which of the following Lewis electron-dot diagrams represents the molecule that contains the smallest bond angle?
NF3 .. .. .. :F- N - F: .. l .. :F: "
Which statement best helps to explain the observation that NH3(l)NH3(l) boils at −28°C−28°C, whereas PH3(l)PH3(l) boils at −126°C−126°C?
NH3 has hydrogen bonding that is stronger than the dipole-dipole forces in PH3.
Which of the following is incorrectly named
NO3-, nitrite ion
Which of the following could be the identity of a white crystalline solid that exhibits the following properties? It melts at 320°C. It does not conduct electricity as a solid. It conducts electricity in an aqueous solution.
NaOH(s)
Resonance is most commonly used to describe the bonding in molecules of which of the following?
O3
5 H2O2(aq) + 2 MnO4-(aq) + 6 H+(aq) → 2 Mn2+(aq) + 8 H2O(l) + 5 O2(g) In a titration experiment, H2O2(aq) reacts with aqueous MnO4-(aq) as represented by the equation above. The dark purple KMnO4 solution is added from a buret to a colorless, acidified solution of H2O2(aq) in an Erlenmeyer flask. (Note: At the end point of the titration, the solution is a pale pink color.) Which element is being oxidized during the titration, and what is the element's change in oxidation number?
Oxygen, which changes from -1 to 0
Of the following single bonds, which is the LEAST polar? N-H H-F O-F I-F O-H
O—F
A precipitation reaction
Pb2+(aq) + CrO42-(aq) → PbCrO4(s)
Equal volumes of 0.2M solutions of lead(II) nitrate and potassium bromide are combined to form lead(II) bromide as a yellow precipitate. Which of the following is the correct net ionic equation for the reaction?
Pb2+(aq)+2Br-(aq)→PbBr2(s)
As part of the calibration of a new laboratory balance, a 1.000-g mass is weighed with the following results: Trial Mass 1 1.201 +- 0.001 2 1.202 +- 0.001 3 1.200 +- 0.001
Precise but inaccurate
How many protons, neutrons, and electrons are in an 56 26 Fe atom?
Protons - 26 Neutrons - 30 Electrons - 26
Based on the information above and periodic trends, which of the following is the best hypothesis regarding the oxide(s) formed by Rb?
Rb will form Rb2O, Rb2O2, and RbO2.
To determine the percentage of water in a hydrated salt, a student heated a 1.2346 g sample of the salt for 30 minutes; when cooled to room temperature, the sample weighed 1.1857 g. After the sample was heated for an additional 10 minutes and again cooled to room temperature, the sample weighed 1.1632 g. Which of the following should the student do next?
Reheat the sample until its mass is constant.
A compound contains 30. percent sulfur and 70. percent fluorine by mass. The empirical formula of the compound is
SF4
The reaction between aqueous strontium chloride (SrCl2) and aqueous potassium sulfate (K2SO4) forms a precipitate of strontium sulfate (SrSO4)(SrSO4). Which of the following represents the net ionic equation for the reaction?
Sr2+(aq)+SO42−(aq)→SrSO4(s)
2F2(g)+2NaOH(aq)→OF2(g)+2NaF(aq)+H2O(l) A 2mol sample of F2(g) reacts with excess NaOH(aq) according to the equation above. If the reaction is repeated with excess NaOH(aq) but with 1 mol of F2(g), which of the following is correct?
The amount of OF2(g)OF2(g) produced is halved.
The potential energy of a system of two atoms as a function of their internuclear distance is shown in the diagram above. Which of the following is true regarding the forces between the atoms when their internuclear distance is x?
The attractive and repulsive forces are balanced, so the atoms will maintain an average internuclear distance x.
A 1L sample of helium gas at 25°C and 1atm is combined with a 1L sample of neon gas at 25°C and 1atm. The temperature is kept constant. Which of the following statements about combining the gases is correct?
The average kinetic energy of the helium atoms and neon atoms do not change when the gases are combined.
The elements CC and Se have the same electronegativity value, 2.55. Which of the following claims about the compound that forms from CC and SeSe is most likely to be true?
The carbon-to-selenium bond is nonpolar covalent.
A vessel contains Ar(g) at a high pressure. Which of the following statements best helps to explain why the measured pressure is significantly greater than the pressure calculated using the ideal gas law?
The combined volume of the Ar atoms is too large to be negligible compared with the total volume of the container.
After completing an experiment to determine gravimetrically the percentage of water in a hydrate, a student reported a value of 38 percent. The correct value for the percentage of water in the hydrate is 51 percent. Which of the following is the most likely explanation for this difference?
The dehydrated sample absorbed moisture after heating.
For element X represented above, which of the following is the most likely explanation for the large difference between the second and third ionization energies?
The electron removed during the third ionization is, on average, much closer to the nucleus than the first two electrons removed were.
The diagrams above represent two samples of Xe gas in containers of equal volume at 280K. Which of the following correctly compares the two samples in terms of their deviation from ideal gas behavior and explains why?
The gas in sample 2 would deviate more from ideal behavior because the Xe atoms are closer together, leading to an increase in intermolecular attractions.
C6H12O6+6O2→6CO2+6H2O The reaction between C6H12O6 and O2 is represented by the balanced equation above. In an experiment, 0.30mol of CO2 was produced from the reaction of 0.05mol of C6H12O6 with excess O2. The reaction was repeated at the same temperature and in the same container, but this time 0.60mol of CO2 was produced. Which of the following must be true?
The initial amount of C6H12O6 in the container must have been 0.10mol .
A student places a sample of a pure metal in a crucible and heats it strongly in air. Data from the experiment are given in the table above. The final mass was determined after the sample was cooled to room temperature. Which of the following statements related to the experiment is correct?
The mass of the sample increased, so a chemical change occurred when bonds formed between the metal and another substance.
Which of the following is an example of quantitative observation?
The temperature of the liquid is 60°C.
HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l)HCl(aq)+NaOH(aq)→NaCl(aq)+H2O(l) A student had two dilute, colorless solutions, HCl(aq) and NaOH(aq), which were at the same temperature. The student combined the solutions, and the reaction represented above occurred. Which of the following results would be evidence that a chemical reaction took place?
The temperature of the reaction mixture increases.
The table above shows the first ionization energy and atomic radius of several elements. Which of the following best helps to explain the deviation of the first ionization energy of oxygen from the overall trend?
There is repulsion between paired electrons in oxygen's 2p orbitals.
The BF3 molecule is nonpolar, whereas the NF3 molecule is polar. Which of the following statements accounts for the difference in polarity of the two molecules?
Unlike BF3, NF3 has a nonplanar geometry due to an unshared pair of electrons on the N atom.
MgCl2(aq)+2NaOH(aq)→2NaCl(aq)+Mg(OH)2(s) A 100mL sample of 0.1M MgCl2(aq) and a 100mL sample of 0.2MNaOH(aq) were combined, and Mg(OH)2(s) precipitated, as shown by the equation above. If the experiment is repeated using solutions of the same molarity, which of the following changes in volume will double the amount of Mg(OH)2(s) produced?
Using twice the volume of MgCl2(aq)MgCl2(aq) and twice the volume of NaOH(aq)
The potential energy as a function of internuclear distance for three diatomic molecules, X2, Y2, and Z2, is shown in the graph above. Based on the data in the graph, which of the following correctly identifies the diatomic molecules, X2, Y2, and Z2?
X2 Y2 Z2 H2 N2 O2
Zn2+ - 74 Ca2+ - 100 Ba2+ - 135 Based on the data in the table above, which of the following correctly predicts the relative strength of the attraction of Zn2+, Ca2+, and Ba2+ ions to water molecules in a solution, from strongest to weakest, and provides the correct reason?
Zn2+ > Ca2+ > Ba2+ because the smaller ions have a stronger coulombic attraction to water
Which of the following names is incorrect?
aluminum (III) oxide
A solution is also called a
homogenous mixture
According to the VSEPR model, the progressive decrease in the bond angles in the series of molecules CH4, NH3, and H2O is best accounted for by the
increasing number of unshared pairs of electrons
Classify the following molecule: O II H3C-C-CH2CH3
ketone
The state of matter for an object that has a definite volume but not a definite shape is
liquid state
The correct name for LiCl is
lithium chloride
Order the four metric prefixes from smaller to largest
nano- < milli- < centi- < centi- < kilo-
Name the following: Ch3-(CH2)6-CH3
octane
Which best represents a solid element?
option b(aligned, no gaps)
Which best represents a gaseous compound?
option c, (tow circle attached to eachother, floating)
Which represents a heterogenous mixture of two elements
option d (two colors of circles)
Which best represents a homogenous mixture of an element and a compound?
option e (squares, and two circles)
The state of matter for an object that has both definite volume and definite shape is
solid state