AP Chem Final

1.2 atm

2 H₂O₂(aq) → 2 H₂O(l) + O₂(g) ∆H° = -196 kJ/mol The decomposition of H₂O₂(aq) os represented by the equation above. A student monitored the decomposition of a 1.0 L sample of H₂O₂(aq) at a constant temperature of 300°K and recorded the concentration of H₂O₂ as a function of time. The results are given in the table below. Time (s) [H₂O₂] 0 2.7 200 2.1 400 1.7 600 1.4 The O₂(g) produced from the decomposition of the 1.0 L sample of H₂O₂(aq) is collected om a previously evacuated 10.0 L flask at 300°K. What is the approximate pressure in the flask after 400 s? (For estimation purposes, assume that 1.0 mole of gas in 1.0 L exerts a pressure of 24 atm at 300°K).

∆G°: Negative ∆S°: Positive

2 H₂O₂(aq) → 2 H₂O(l) + O₂(g) ∆H° = -196 kJ/mol The decomposition of H₂O₂(aq) os represented by the equation above. A student monitored the decomposition of a 1.0 L sample of H₂O₂(aq) at a constant temperature of 300°K and recorded the concentration of H₂O₂ as a function of time. The results are given in the table below. Time (s) [H₂O₂] 0 2.7 200 2.1 400 1.7 600 1.4 The reaction is thermodynamically favorable. The signs of ∆G° and ∆S° for the reaction are which of the following?

Oxygen is both oxidized and reduced.

2 H₂O₂(aq) → 2 H₂O(l) + O₂(g) ∆H° = -196 kJ/mol The decomposition of H₂O₂(aq) os represented by the equation above. A student monitored the decomposition of a 1.0 L sample of H₂O₂(aq) at a constant temperature of 300°K and recorded the concentration of H₂O₂ as a function of time. The results are given in the table below. Time (s) [H₂O₂] 0 2.7 200 2.1 400 1.7 600 1.4 Which of the following identified the element(s) being oxidized and reduced in the reaction?

The reaction is first order if the plot of ln [H₂O₂] versus time is a straight line.

2 H₂O₂(aq) → 2 H₂O(l) + O₂(g) ∆H° = -196 kJ/mol The decomposition of H₂O₂(aq) os represented by the equation above. A student monitored the decomposition of a 1.0 L sample of H₂O₂(aq) at a constant temperature of 300°K and recorded the concentration of H₂O₂ as a function of time. The results are given in the table below. Time (s) [H₂O₂] 0 2.7 200 2.1 400 1.7 600 1.4 Which of the following statements is a correct interpretation of the data regarding how the order of the reaction can be determined?

+ 0.68 V

2 H₂O₂(aq) → 2H₂O(l) + O₂(g) E° = o.55 V The equation and standard cell potential for the decomposition of H₂O₂(aq) in acidic solution at 25°C is given above. The reduction had reactions for the process are listed below. O₂(g) + 4 H⁺(aq) + 4 e⁻ → 2 H₂O(l) E° = 1.23 V O₂(g) + 2 H⁺(aq) + 2 e⁻ → H₂O₂(aq) E° = ? O₂(g) + 2 H⁺(aq) + 2 e⁻ → H₂O₂(aq) What is the standard reduction potential for the half reaction represented above?

∆G° < 0 and Keq < 1

2 H₂O₂(aq) → 2H₂O(l) + O₂(g) E° = o.55 V The equation and standard cell potential for the decomposition of H₂O₂(aq) in acidic solution at 25°C is given above. The reduction had reactions for the process are listed below. O₂(g) + 4 H⁺(aq) + 4 e⁻ → 2 H₂O(l) E° = 1.23 V O₂(g) + 2 H⁺(aq) + 2 e⁻ → H₂O₂(aq) E° = ? Which of the following is true for the decomposition of H₂O₂(aq)?

NO₂(g) + F₂(g) → NO₂F(g) + F(g)

2 NO₂(g) + F₂(g) → 2 NO₂F(g) The rate law for the reaction represented by the equation above is rate = k [NO₂] [F₂}. Which of the following could be the first elementary step of a two step mechanism for the reaction if the first step is flow and the second step is fast?

The reaction will form more reactant.

2XY(g) ⇌ X₂(g) + Y₂(g) Kp = 230 A certain gas, XY(g), decomposes as represented by the equation above. A sample of each of the three gases is put in a previously evacuated container. The initial partial pressure of the gases are shown in the table below. Gas Initial partial pressure (atm) XY 0.010 X₂. 0.20 Y₂ 2.0 The temperature of the reaction mixture is held constant. In which direction will the reaction proceed?

5

A 0.35g sample of Li(s) is placed in an Erlenmeyer flask containing 100 mL of water at 25°C. A balloon is placed over the mouth of the flask to collect the hydrogen gas that is generated. After all of the Li(s) has reacted with H₂O(l), the solution in the flask is added to a clean, dry buret and used to titrate an aqueous solution of a monophonic acid. The pH curve for this titration is shown in the diagram below. On the basis of the pH curve, the pKa value of the acid is closest to...

Some gas will be produced but less than the amount of gas produced with Li(s).

A 0.35g sample of Li(s) is placed in an Erlenmeyer flask containing 100 mL of water at 25°C. A balloon is placed over the mouth of the flask to collect the hydrogen gas that is generated. After all of the Li(s) has reacted with H₂O(l), the solution in the flask is added to a clean, dry buret and used to titrate an aqueous solution of a monophonic acid. The pH curve for this titration is shown in the diagram below. What will be the effect on the amount of gas produced if the experiment is repeated using 0.35g of K(s) instead of0.35g of Li(s)?

Using a 0.35 g sample of Li(s) cut into small pieces.

A 0.35g sample of Li(s) is placed in an Erlenmeyer flask containing 100 mL of water at 25°C. A balloon is placed over the mouth of the flask to collect the hydrogen gas that is generated. After all of the Li(s) has reacted with H₂O(l), the solution in the flask is added to a clean, dry buret and used to titrate an aqueous solution of a monophonic acid. The pH curve for this titration is shown in the diagram below. Which of the following changes will most likely increase the rate of reaction between Li(s) and water?

2 Li(s) + 2 H₂O(l) → 2 Li⁺(aq) + 2 OH⁻(aq) + H₂(g)

A 0.35g sample of Li(s) is placed in an Erlenmeyer flask containing 100 mL of water at 25°C. A balloon is placed over the mouth of the flask to collect the hydrogen gas that is generated. After all of the Li(s) has reacted with H₂O(l), the solution in the flask is added to a clean, dry buret and used to titrate an aqueous solution of a monophonic acid. The pH curve for this titration is shown in the diagram below. Which of the following is the balanced net ionic equation for the reaction between Li(s) and water?

He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms.

A 0.5 mole sample of Ne(g) are placed separately in two 10.0 L rigid containers at 25C. Each container has a pinhole opening. Which of the gases, He or Ne, escape faster through the pinhole and why?

The combustion of 1.0g of cashew releases more energy than the combustion of 1.0g of marshmallow.

A 1.0g sample of a cashew was burned in a calorimeter containing 1000g of water, and the temperature of the water changed from 20°C to 25°C. In another experiment, a 3.0g sample of a marshmallow was burned in a calorimeter containing 2000g of water, and the temperature of the water changed from 25°C to 30°C. Based on the data, which of the following can be concluded about the energy content of 1.0g of each of the two substances? (The specific heat of water is 4.2 J/(g°C).)

C₂H₆O

A 23 g sample of a compound contains 12 g of C, 3 g of H, and 8 g of O. Which of the following is the empirical formula of the compound?

60°C

A hot iron ball is dropped into a 200 g sample of water initially at 50°C. If 8.4 kJ of heat is transferred from the ball to the water, what is the final temperature of the water? (The specific heat of water is 4.2 J/(g°C).)

It is not a good conductor of electricity because it's valence electrons are located in bonding and nonbonding pairs.

A room temperature I₂(g) is a molecular solid. Which of the following provides a characteristic of I₂(s) with a correct explanation?

CH₅N

A sample compound that contains only the elements C, H, and N is completely burned in O₂ to produce 44.0g of CO₂, 45.0g of H₂O, and some NO₂. A possible empirical formula of the compound is

ionic bonds

A sample of hard, solid binary compound at room temperature did not conduct electricity as a pure solid but became conductive when dissolved in water. Which of the following types of interactions is most likely found between the particles in the substance?

The combined volume of the Ar atoms is too large to be negligible compared with the total volume of the container.

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?

solution C

Acid solution Volume of NaOH added (mL) A 40 B 75 C 115 D 200 To maximize the yield in a certain manufacturing process, a solution of a weak monophonic acid that has a concentration between 0.20 M and 0.30 M is required. Four 100 mL samples of the acid at different concentration are each titrated with a 0.20 M NaOH solution. The volume of NaOH needed to reach the end point for each sample is given in the table above. Which solution is the most suitable to maximize the yield?

The precipitate was not rinsed with deionized water before drying.

AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq) A student performed an analysis to determine the amount of AgNO₃(aq) in a solution. Excess NaCl(aq) was added to the solution, and the Ag⁺(aq) precipitated as AgCl(s). The precipitate was collected by gravity filtration and dried in an oven. Three trials were performed, and in each case, according to the instructor, the mass of precipitate recovered was 5 percent higher than the actual mass of AgCl(s) that should have formed. Which of the following could account for the error?

Only PbSO₄(s) will precipitate.

Ag₂SO₄ Ksp @ 298 K = 1x10⁻⁵ PbSO₄ Ksp @ 298 K = 1x10⁻⁸ A 1.0 L solution of AgNO₃(aq) and Pb(NO₃)₂ has a Ag⁺ concentration of 0.020 M and a Pb²⁺ concentration of 0.001 M. A 0.001 mol sample of K₂SO₄(s) iOS added to the solution. Based on the information in the table above, which of the following will occur? (Assume that the volume change of the solution is negligible.)

Acetate Species: C₂H₃O₂⁻ pH: > 4.7

An acetate buffer solution is prepared by combining 50 mL of a 0.20 M acetic acid, HC₂H₃O₂(aq), and 50 mL of 0.20 M sodium acetate, NaC₂H₃O₂(aq). A 5.0 mL sample of 0.10 M NaOH(aq) is added to the buffer solution. Which of the following is a correct pairing of the acetate species present in greater concentration and of the pH solution after the NaOH(aq) is added? (The pKa of scenic acid is 4.7).

[CO₂] > [CO]

CO(g) + H₂O(g) ⇌ CO₂(g) + H₂(g) Kc = 1.5x10³ A 2.0 mol sample of CO(g) and a 2.0 mol sample of H₂O(g) are introduced into a previously evacuated 100 L rigid container, and the temperature is held constant as the reaction represented above reaches equilibrium. Which of the following is true at equilibrium?

CS₂(l), because it has weaker LDF

CS₂(l) 76 g/mol BP: 46.5°C CCl₄(l) 154 g/mol BP: 76.7°C Based on the info in the table above, which liquid has the higher equilibrium vapor pressure at 25°C, and why?

lowering the temperature of the system

CaCO₃(s) ⇌ CaO(s) + CO₂(g) ∆H° = 178 kj/mol The reaction system represented above is at equilibrium. Which of the following will decrease the amount of CaO(s) in the system?

PbCl₂

Compound Ksp PbCl₂ 1.2 x 10⁻⁵ CuCl 1.6 x 10⁻⁷ AgCl 1.8 x 10⁻¹⁰ Hg₂Cl₂ 1.4 x 10⁻¹⁸ Based on the Ksp values in the table above, a saturated solution of which of the following compounds has the highest [Cl-]?

Adding a heterogenous catalyst to the reaction system

C₂H₄(g) + H₂(g) → C₂H₆(g) Which of the following will most likely increase the rate of the reaction represented above?

A mixture of 100 mL of 0.1 M HC₃H₅O₃ and 50 mL of 0.1 M NaOH

HC₃H₅O₃(aq) Ka: 8.3 x 10⁻⁴ CH₃NH₃⁺(aq) Ka: 2.3 x 10⁻¹¹ The acid dissociation constants of HC₃H₅O₃(aq) and CH₃NH₃⁺(aq) are given in the table above. Which of the following mixtures is a buffer with a pH of approximately 3?

distilled water

HF(aq) + H₂O(l) → C₂H₂(g) + Ca(OH)₂(s) The dissociation of the weak acid HF in water is represented by the equation above. Adding a 1.0 mL sample of which of the following would increase the percent ionization of HF(aq) in 10 mL of a solution of 1.0 M HF?

Y⁻(aq)

HX(aq) + Y⁻(aq) ⇌ HY(aq) + X⁻(aq) A solution of a salt of a weak acid HY is added to a solution of another weak acid HX. Based on the information given above, which of the following species is the strongest base?

HX(aq)

HX(aq) + Y⁻(aq) ⇌ HY(aq) + X⁻(aq) key > 1 Based on the information given above, which of the following is the strongest acid?

PO₄³⁻

H₃PO₄ ⇌ H⁺ + H₂PO₄⁻ Ka₁ = 7.2 x 10⁻³ H₂PO₄⁻ ⇌ H⁺ + HPO₄²⁻ Ka² = 6.3 x 10⁻⁸ HPO₄²⁻ ⇌ H⁺ + PO₄³⁻ Ka³ = 4.5 x 10⁻¹³ A solution is prepared by mixing 50 mL of 1 M NaH₂PO₄. On the basis of the information above, which of the following species is present in the solution at the lowest concentration?

Benzene, C₆H₆

If equal masses of the following compounds undergo complete combustion, which will yield the greatest mass of CO₂?

CH₂F₂(l)

In which of the following liquids do the intermolecular forces include dipole-dipole forces?

Decreasing the pH.

Mg(OH)₂(s) ⇌ 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 1.8 x 10⁻¹¹. Which of the following changes will increase the solubility go Mg(OH)₂ in aqueous solution.

Adding some N₂(g)

N₂(g) + 3 H₂(g) ⇌ 2 NH₃(g) ∆H < 0 NH₃(g) was synthesized at 200°C in the presence of a powdered Os(s) catalyst, leading to the equilibrium system represented above. Which of the following changes would result in more NH₃(g) in the mixture after equilibrium is reestablished?

Ca(OH)₂ will not precipitate because Q > Ksp

Reaction 1: CaC₂(s) + 2 H₂O(l) → C₂H₂(g) + Ca(OH)₂(s) Reaction 2: NaOCl(aq) + 2 HCl (aq) → Cl₂(g) + NaCl(aq) + H₂O(l) Reaction 3: C₂H₂(g) + Cl₂(g) → C₂H₂Cl₂(g) Ca(OH)₂(s) precipitate when a 1.0g sample of CaC₂(s) is added to 1.0 L of distilled water at room temperature. If a 0.064g sample of CaC₂(s) (molar mass 64g/mol) is used instead all of it reacts, which of the following will occur and why?

0.10 M

Reaction 1: CaC₂(s) + 2 H₂O(l) → C₂H₂(g) + Ca(OH)₂(s) Reaction 2: NaOCl(aq) + 2 HCl (aq) → Cl₂(g) + NaCl(aq) + H₂O(l) Reaction 3: C₂H₂(g) + Cl₂(g) → C₂H₂Cl₂(g) Reaction 2 occurs when an excess of 6 M HCl(aq) solution is added to 100 mL of NaOCl(aq) of unknown concentration. If the reaction goes to completion and 0.010 mol of Cl₂(g) is produced, then what was the molarity of the NaOCl(aq) solution?

Yes; it changes from sp to sp²

Reaction 1: CaC₂(s) + 2 H₂O(l) → C₂H₂(g) + Ca(OH)₂(s) Reaction 2: NaOCl(aq) + 2 HCl (aq) → Cl₂(g) + NaCl(aq) + H₂O(l) Reaction 3: C₂H₂(g) + Cl₂(g) → C₂H₂Cl₂(g) When reaction 3 occurs, does the hybridization of the carbon atoms change?

Solution 1 has a higher pH at the equivalence point because CH₃CO₂H has a stronger conjugate base.

Solution Acid Ka 1 CH₃CO₂H 1.75 x 10⁻⁵ 2 CF₃CO₂H 1.0 x 10⁰ Acid dissociation constants of two acids are listed in the table above. A 20 mL sample of a 0.10 M solution of each acid is titrated to the equivalence point with 20 mL of 0.10 M NaOH. Which of the following is a true statement about the pH of the solutions at the equivalence point?

Mg²⁺(g) and O²⁻(g)

The lattice energy of a salt is related to the energy required to separate the ions. For which of the following pairs of ions is the energy that is required to separate the ions largest? (Assume that the distance between the ions in each pair is equal to the sum of the ionic radii).

between 2 and 3

The pH of a 0.01 M HNO₂(aq) solution is in which of the following ranges? (For HNO₂(aq), Ka = 4x10⁻⁴)

Adding a solution containing an anion that forms an insoluble salt with only one of the metal ions.

To gravimetrically analyze the silver content of a piece of jewelry made from an alloy of Ag and Cu, a student dissolves a small pre weighted sample in HNO₃(aq), Ag⁺(aq) and Cu²⁺(aq) ions form in the solution. Which of the following should be the next step in the analytical process?

LR: Na₂O₂ q = 30kj

When water is added to a mixture of Na₂O₂(s) and S(s), a redox reaction occurs, as represented by the equation below. 2 Na₂O₂(s) + S(s) + 2 H₂O(l) → 4NaOH(aq) + SO₂(aq) ∆H₂₉₈° = -610 kJ/mol; ∆S₂₉₈° = -7.3 J/mol Two trials are run, using excess water. In the first trial, 7.8g of Na₂O₂(s) (molar mass 78g/mol) is mixed with 3.2g of S(s). In the second trial, 7.8g of Na₂O₂(s) is mixed with 6.4g of S(s). The Na₂O₂(s) and S(s) react as completely as possible. Both trials yield the same amount of SO₂(aq). Which of the following identifies the limiting reactant and the heat released, q, for the two trials at 298 K?

At 37°C the auto ionization constant for water, Kw, is larger than it is at 25°.

Which of the following accounts for the observation that the pH of pure water at 37°C is 6.8?

F₂ < O₂ < N₂

Which of the following arranges the molecules N₂, O₂, and F₂ in order of their bond enthalpies, from least to greatest?

At higher temperatures, high energy collisions happen more frequently.

Which of the following best help explain why an increase in temperature increases the rate of a chemical reaction?

[R] = [Z] > [Q]

X(g) + 2 Q(g) ⇌ R(g) + Z(g) Kc = 1.3 x 10⁵ at 50°C A 1.0 mole sample of X(g) and 1.0 mol sample of Q(g) are introduced into an evacuated, rigid 10.0 L container and allowed to reach equilibrium at 50°C according to the equation above. At equilibrium, which of the following is true about the concentrations of the gases?