AP Chemistry Test Thermodynamics multiple choice

1 calorie

4.184 joules

Which of the letters on the graph best describes the flow of heat into the surroundings when 1 mol of XY2 decomposes?

A

Which of the following processes involves the greatest increase in entropy?

A- MgSO3(s) > MgO(s) + SO2(g)

Mg(OH)2 <> Mg2+ (aq) + 2OH-(aq) the exothermic dissolution of Mg(OH)2(s) in water is represented by the equation above. the Ksp of Mg(OH)2 is 1.8x10-11. which of the following changes will increase the solubility of Mg(OH)2 in an aqueous solution?

A- decreasing the pH

Potassium hydrogen phthalae, KHP, is used as a primary standard for determining the concentration of a solution of NaOH by titration. if the KHP has not been dried before weighing, the calculated molarity of the NaOH would be

A- higher than the actual value, since water is included in the apparent mass of KHP

The enthalpy of vaporization of water is 40.7kJ/mol. which of the following best explains why the enthalpy of vaporization of methane is less than that of water?

A- methane does not exhibit hydrogen bonding, but water does

N2(g) + 3H2(g) <> 2NH3(g) delta H=-92kJ/mol; delta G=-33kJ/mol. consider the reaction represented above at 298K. when equal volumes of N2(g) and H2(g), each at 1atm, are mixed in a closed container at 298K, no formation of NH3(g) is observed. which of the following best explains the observation?

A- the N2(g) and the H2(g) must mix in a 1:3 ratio for a reaction to occur

the heating curve for a sample of pure water is provided. the temperature was recorded as a 50g sample of solid water was heated at a constant rate. which of the following explains why the slope of the segment of steam is greater than the slope of segment liquid water?

A- the specific heat capacity of gaseous ethanol is less than the specific heat capacity of liquid ethonol

a 20g cube of copper at a temperature T1, is placed in an insulated cup containing 10g of water at a temperature T2. if T1>T2, which of the following is true of the system when it has attained thermal equilibrium?

A- the temperature of the copper changed more than the temperature of the water

NaOH(aq) + HCl(aq)> H2O(l) + NaCl(aq) a student is trying to determine the heat of reaction for the acid base neutralization reaction represented above. the student uses .5M NaOH and .5M HCl solutions. Which of the following situations, by itself, would most likely result in the least error in the calculated value of the heat of reaction?

A- thermometer incorrectly calibrated 5C too high

Which of the following best explains why more energy is required for the process occurring at 110K than for the process occurring at 90K?

A-intermolecular attractions are completely overcome during vaporization

A 1 mol sample of CO(g) and 1 mol sample of H2(g) are pumped into a rigid, previously evacuated 2L reaction vessel at 483K. Which of the following is true at equilibrium?

B- [H2]<[CO]

A 1 mol sample of CO(g) and H2(g) is pumped into a preciously evacuated 2L reaction vessel. the total pressure of the reaction system is 1.2 atm at equilibrium. What will be the total pressure of the system if the volume of the reaction vessel is reduced to 1L at constant temperature?

B- greater than 1.2 but less than 2.4 atm

Based on the data, which of the following are the approximate pKa of the acid and the molar concentration of the NaOH?

B- pKa 4.7 [NaOH] .1M

The date in the table above were obtained for the reaction X+Y>Z. which of the following is the rate law for the reaction?

B- rate= [Y]2

On the basis on the information above, the dissolution of FeF2(s) in an acidic solution is

B- thermodynamically favorable because K3>1

Which of the following equations represents a reaction for which the standard entropy change is positive?

C- CaCO3(s)> CaO(s) + CO2(g)

A solution containing HCl and the weak acid HClO4 has a pH of 2.4. enough KOH(aq) is added to the solution to increase the pH to 10.5. the amount of which of the following species increases as the KOH(aq) is added?

C- ClO2-

A solution is prepared by adding 100mL of 1M HC2H3O2(g) to 100mL of 1 M NaC2H3O2(aq). the solution is stirred and its pH is measured to be 4.73. after 3 drops of 1 m HCl are added to the solution, the pH of the solution is measured and is still 4.73. which of the following equations represents the chemical reaction that accounts for the fact that acid was added but there was no detectable change in pH?

C- H3O+(aq) + C2H3O2- > HC2H3O2(aq) + H2O(l)

Which of the following explains the effect on the equilibrium constant Kc, when the temperature of the reaction system is increased to 650K?

C- Kc will decrease because the reaction is exothermic

The reaction is thermodynamically favorable under standard conditions at 298K. therefore, the value of delta S for the reaction must be

C- greater than delta H/ 293K

a 1g sample of a cashew was burned in a calorimeter containing 1000g of water, and the temperature of the water changed from 20C to 25C. in another experiment, a 3g sample of a marshmallow was burned in a calorimeter containing 2000g of water, and the temperature of the water changed from 25C to 30C. based on the data, which of the following can be concluded about the energy fontent for 1g of the two substances?

C- the combustion of 1g of cashew releases more energy than the combustion of 1g of marshmallow

Which of the following statements is true about bond energies in this reaction?

C- the energy absorbed as the bonds in the reactants are broken is less than the energy released as the bonds in the product are formed

Which of the following best helps to explain why the value of delta H for the dissolving of CaF2 in water is positive?

Ca 2+ ions have a very strong ion-ion interactions with F- ions in the crystal lattice

write the ionic formula: iron(III) acetate

Fe(C2H3O2)3

write the ionic formula: iron(II) acetate

Fe(C3H3O2)2

For which of following reaction mixtures at equilibrium would reducing the volume of the container at a constant temperature cause the equilibrium to shift toward the products?

D- 2NO2(g)<>N2O4(g)

2H2(g) + O2(g) > 2H2O(g) for the reaction above at 25C, what are the signs of delata H, S, and G

D- all negative

based on the information above, which of the following statements is true?

D- as the temperature increases, the pH of pure water decreases

Which of the following most likely accounts for the difference between reaction path one and reaction path two?

D- the presence of a catalyst in path two

write the ionic formula: potassium phosphate

K3PO4

write the ionic formula: sodium sulfate

Na2SO4

Atoms of Mg combine with atoms of F to form a compound. Atoms of which of the element families combine with the atom F to form the same ratio?

alkaline earth metals

What makes a substance a strong electrolyte when dissolved in water?

sodium nitrate