CHM115 Practice Quiz 2

26. Calculate the pH of 0.208 M HNO3(aq). A) 0.682 B) 2.080 C) -1.140 D) 13.792 E) 1.570

A) 0.682

For the following reaction at equilibrium, which one of the changes below would cause the equilibrium to shift to the left? 2NOBr(g) → 2NO(g) + Br2(g), ∆Hºrxn = 30 kJ/mol A) Decrease the temperature. B) Increase the container volume. C) Remove some NO. D) Remove some Br2 . E) Add more NOBr.

A) Decrease the temperature.

Which of the following indicates the most basic solution? A) [H+ ] = 1 × 10-10 M B) pOH = 6.7 C) [OH- ] = 7 × 10-5 M D) pH = 4.2 E) At least two of the solutions are equally basic.

A) [H+ ] = 1 × 10-10 M

What concentration of HOCl (Ka = 3.5 × 10-8) has the same pH as that of 2.50 × 10-4 M HNO3? A). 1.79 M B). 6.80 × 10-8 M C). 3.50 × 10-2 M D). 3.93 M E). 0.560 M

A). 1.79 M

A 0.14 M HNO2 solution is 5.7% ionized. Calculate the H+ ion concentration. Ka (HNO2) = 4.5 × 10-4 A). 8.0 x 10-3 M B). 0.057 M C). 0.13 M D). 0.14 M E). 0.80 M

A). 8.0 x 10-3 M

The expression for Kp, for the reaction below is __________. 4CuO (s) + CH4 (g) CO2 (g) + 4Cu (s) + 2H2O (g) A. (PCO2)( PH2O)2 / (PCH4) B. (PCH4) / (PH2O)2 (PCO2) C. [Cu](PCO2)(PH2O)2 / [CuO]4 (PCH4) D. (PCH4) / (PCO2)(PH2) 2 E. (PCO2)(PH2O)2 / (PCuO)

A. (PCO2)( PH2O)2 / (PCH4)

The value of Keq for the equilibrium H2 (g) + I2 (g) 2 HI (g) is 794 at 25°C. At this temperature, what is the value of Keq for the equilibrium below? HI (g) 1/2 H2 (g) + 1/2 I2 (g) A. 0.035 B. 0.0013 C. 28 D. 397 E. 1588

A. 0.035

What is the Ka of the weak acid HClO2 if a 0.106 M solution of the acid has a pH = 2.22? (Note: Calculate % ionization to determine if change (x) is negligible) A. 3.6 × 10-4 B. 6.0 × 10-3 C. 1.6 × 10-3 D. 5.9 × 10-4 E. 1.3 × 10-2

A. 3.6 × 10-4

The effect of a catalyst on an equilibrium is to __________. A. increase the rate at which equilibrium is achieved without changing the composition of the equilibrium mixture B. increase the rate of the forward reaction only C. shift the equilibrium to the right D. increase the equilibrium constant so that products are favored E. slow the reverse reaction only 4

A. increase the rate at which equilibrium is achieved without changing the composition of the equilibrium mixture

What is the [H2PO4 -] of a solution labeled "0.10 M Phosphoric Acid (H3PO4)"? [Ka1 = 7.1 × 10-3 ; Ka2 = 6.3 × 10-8 ; Ka3 = 4.2 × 10-13] A) 4.2 × 10-13 M B) 2.7 × 10-2 M C) 7.1 × 10-3 M D) 1.6 × 10-9 M E) 1.6 × 10-16 M

B) 2.7 × 10-2 M

The pain killer morphine is a weak base when added to water. The Kb is 1.6 × 10-6. What is the pH of a 4.07 × 10-3 M solution of morphine? A) 4.09 B) 9.91 C) 5.81 D) 9.41 E) none of these

B) 9.91

Consider the reaction HOCl + F- HF + OCl- Given that Ka for HOCl is 3.5 × 10-8 and the Ka for HF is 7.2 × 10-4 (both at 25°C), which of the following is true concerning K for the above reaction at 25°C? A) K is greater than 1. B) K is less than 1. C) K is equal to 1. D) Cannot be determined with the above information. E) None of these (A-D).

B) K is less than 1

The OH- ion concentration of a blood sample is 2.3 × 10-7 M. What is the pH of the blood? A). 7.18 B). 7.4 C). 14.00 D). 7.00 E). 6.6

B). 7.4

What are the pH and pOH for a 0.025 M KOH solution? A). pH = +1.60 and pOH =+12.40 B). pH = +12.40 and pOH = +1.60 C). pH = -12.40 and pOH = -1.60 D). pH = +12.40 and pOH = -1.60 E). pH = -1.60 and pOH = +1.60

B). pH = +12.40 and pOH = +1.60

Nitrosyl bromide decomposes according to the following equation. 2NOBr (g) 2NO (g) + Br2 (g) A sample of NOBr (0.64 mol) was placed in a 1.00-L flask containing no NO or Br2. At equilibrium the flask contained 0.46 mol of NOBr. How many moles of NO and Br2, respectively, are in the flask at equilibrium? A. 0.46, 0.23 B. 0.18, 0.090 C. 0.46, 0.46 D. 0.18, 0.360 E. 0.18, 0.18

B. 0.18, 0.090

At 200°C, the equilibrium constant, Kp, for the reaction below is 2.40 X 103 . 2NO (g) N2 (g) + O2 (g) A closed vessel is injected with 36.1 atm of NO. At equilibrium, the partial pressure of O2 is __________ atm. A. 35.7 B. 17.8 C. 1.50 X 10-2 D. 6.00 E. 294

B. 17.8

Which list gives equal concentrations of the following solutions in order of decreasing acidity? HC3H5O3 (Ka = 1.4 × 10-4) H2O (Ka = 1.0 × 10-14) HOCl (Ka = 3.5 × 10-8) HCN (Ka = 4.9 × 10-10) HCl (Ka = 2 × 106 ) A. HC3H5O3 > HCl > HOCl > HCN > H2O B. HCl > HC3H5O3 > HOCl > HCN > H2O C. HCN > HOCl > HCl > HC3H5O3 > H2O D. HCl > HC3H5O3 > HOCl > H2O > HCN E. H2O > HCN > HOCl > HC3H5O3 > HCl

B. HCl > HC3H5O3 > HOCl > HCN > H2O

. Consider the following reaction at equilibrium. Which of the following situations would cause the maximum number of moles of N2O5 (g) at equilibrium? 2N2(g) + 5O2(g) 2N2O5 (g) ΔH° = + 22 kJ A. High temperature and high volume B. High temperature and low volume C. Low temperature and high volume D. Low temperature and low volume

B. High temperature and low volume

Consider the following reaction at equilibrium: 2CO2 (g) 2CO (g) + O2 (g) ΔH° = -514 kJ Le Chatelier's principle predicts that an increase in temperature will __________. A. increase the partial pressure of O2 (g) B. decrease the value of the equilibrium constant C. increase the partial pressure of CO D. decrease the partial pressure of CO2 (g) E. increase the value of the equilibrium constant

B. decrease the value of the equilibrium constant

Which of the following statements are TRUE, regarding the equilibrium constant K for a reaction and the reaction quotient Q: 1) If Q > K, the reaction is not at equilibrium, and will reach equilibrium by shifting some products over to reactants 2) If K= 5.2 x 104 , the reaction is product favored 3) If K= 3.2 x 10-6, the reaction is product favored 4) If Q = K, the reaction is already at equilibrium. A) 1 and 2 only B) 1, 3, and 4 only C) 1, 2, and 4 only D) 3 and 4 only E) 2 and 4 only

C) 1, 2, and 4 only

If Ka for HCN is 6.20 × 10-10, what is Kb for CN- ? Note: CN- + H2O HCN + OH- Kb HCN + H2O CN- + H3O + Ka A) 6.20 × 10-24 B) 6.20 × 104 C) 1.61 × 10-5 D) 1.24 × 10-9 E) 2.86 × 10-7

C) 1.61 × 10-5

33. A monoprotic weak acid when dissolved in water is 0.36% dissociated and produces a solution with a pH of 3.10. Calculate the Ka of the acid. A) 3.6 × 10-3 B) 2.2 × 10-1 C) 2.9 × 10-6 D) Need to know the initial concentration of the acid. E) None of these.

C) 2.9 × 10-6

At 700 K, the reaction 2SO2(g) + O2(g) → 2SO3(g) has the equilibrium constant Kc = 4.3 × 106 , and the following concentrations are present: [SO2] = 0.10 M; [SO3] = 10. M; [O2] = 0.10 M. Is the mixture at equilibrium? If not at equilibrium, in which direction (as the equation is written), left to right or right to left, will the reaction proceed to reach equilibrium? A) Yes, the mixture is at equilibrium. B) No, right to left C) No, left to right D) There is not enough information to be able to predict the direction.

C) No, left to right

What is Kb if a 0.323 M solution of a weak base has a pH =9.58? A). 4.4 × 10-9 B). 1.3 × 10-4 C). 5.4 × 10-9 D). 1.8 × 10-19 E). 4.2 × 10-5

A). 4.4 × 10-9

For weak acid, HX, Ka = 7.3 × 10-6. Calculate the pH of a 0.59 M solution of HX. A) 0.23 B) 2.68 C) 5.37 D) 11.32 E) none of these

B) 2.68

universal gas constant

R = 0.0821 L atm / mol K

. For the reaction PCl3(g) + Cl2(g) PCl5(g) at a particular temperature, Kc = 24.3. Suppose a system at that temperature is prepared with [PCl3] = 0.10 M, [Cl2] = 0.15 M, and [PCl5] = 0.60M. Which of the following statements is true? A. The reaction is at equilibrium. B. The reaction will proceed in the direction of forming more PCl5 until equilibrium is reached. C. The reaction will proceed in the direction of forming more PCl3 and Cl2 until equilibrium is reached. D. None of the above statements is true.

C. The reaction will proceed in the direction of forming more PCl3 and Cl2 until equilibrium is reached.

12. Consider the following reaction at equilibrium. 2CO2 (g) 2CO (g) + O2 (g) ΔH° = -514 kJ Le Chatelier's principle predicts that the equilibrium partial pressure of CO (g) can be maximized by carrying out the reaction __________. A. at high temperature and high pressure B. at high temperature and low pressure C. at low temperature and low pressure D. at low temperature and high pressure E. in the presence of solid carbon

C. at low temperature and low pressure

Which one of the following will change the value of an equilibrium constant? A. adding other substances that do not react with any of the species involved in the equilibrium B. varying the initial concentrations of reactants C. changing temperature D. varying the initial concentrations of products E. changing the volume of the reaction vessel

C. changing temperature

Fill in the blanks: According to the Brønsted definitions, an acid is a compound that _________ a proton and a base is a compound that ________ a proton. An acid-base reaction involves transfer of a proton from the _________ to the ________. The answers in order are: A. donates, accepts, base, acid B. accepts, donates, base, acid C. donates, accepts, acid, base D. accepts, donates, acid, base

C. donates, accepts, acid, base

Consider the following reaction at equilibrium: 2CO2 (g) 2CO (g) + O2 (g) ΔH° = -514 kJ Le Chatelier's principle predicts that adding O2 (g) to the reaction container will __________. A. decrease the partial pressure of CO2 (g) at equilibrium B. decrease the value of the equilibrium constant C. increase the partial pressure of CO2 (g) at equilibrium D. increase the value of the equilibrium constant E. increase the partial pressure of CO (g) at equilibrium

C. increase the partial pressure of CO2 (g) at equilibrium

At equilibrium, __________. A. the rate constants of the forward and reverse reactions are equal B. all chemical reactions have ceased C. the rates of the forward and reverse reactions are equal D. the value of the equilibrium constant is 1 E. the limiting reagent has been consumed

C. the rates of the forward and reverse reactions are equal

If the following reaction were at equilibrium in a closed vessel at a controlled temperature, what would be the effect of adding more H2 to the reaction vessel and permitting the reaction to approach equilibrium again. CO + H2O <==> CO2 + H2 A. The concentrations of CO, H2O, and H2 would all increase. B. The concentrations of CO, H2O, and H2 would all decrease. C. The concentrations of CO and H2O would increase and the concentration of CO2 would decrease. D. The concentrations of CO and H2O would decrease and the concentration of CO2 would increase.

C.The concentrations of CO and H2O would increase and the concentration of CO2 would decrease.

Consider the following chemical equation: LiCH3 + H2O LiOH + CH4 Which one of the following has the correct label to all the chemicals represented in the above equation? Label Index: Acid (A); Base (B); Conjugate Acid (CA); Conjugate Base (CB) LiCH3 H2O LiOH CH4 (A) (B) (A) (CA) (CB) (B) (A) (B) (CA) (CB) (C) (CB) (CA) (A) (B) (D) (B) (A) (CB) (CA) (E) (CA) (CB) (B) (A)

D

. Determine the percent ionization of a 0.14 M solution of hypochlorous acid, HClO. The Ka for the acid is 3.5 × 10-8 . A) 3.5 × 10-6 % B) 4.9 × 10-9 % C) 7.0 × 10-3 % D) 5.0 × 10-2 % E) 1.58 × 10-1 %

D) 5.0 × 10-2 %

Which of the following is not a conjugate acid-base pair? A) HPO4 2- and PO4 3- B) H3PO4 and H2PO4 - C) H2PO4 - and HPO4 2- D) H2PO4 - and PO4 3- E) H3O + and H2O

D) H2PO4 - and PO4 3-

The solution that will give a pH = 12.00 is (MW: NaOH = 40 g/mol): A. 4.0 g NaOH in 1.0 L of solution. B. 12 g NaOH in 1.0 L of solution. C. 0.20 g NaOH in 2.0 L of solution. D. 0.20 g NaOH in 0.50 L of solution. E. 0.40 g NaOH in 0.10 L of solution.

D. 0.20 g NaOH in 0.50 L of solution.

What is the value of Kc for the reaction 2A(g) + 3B(g) 2C(g) + D(g) if at equilibrium [A] = 0.60 M, [B] = 0.30 M, [C] = 0.10 M and [D] = 0.50 M? A. 1.9 B. 0.15 C. 2.4 D. 0.51 E. 0.088

D. 0.51

Which of the following salts will form a basic solution? A. NaBr B. Ca(NO3)2 C. NH4Cl D. CH3CO2Na E. Al(ClO4)3

D. CH3CO2Na

. Consider the following reactions at equilibrium and determine which of the indicated changes will cause the reaction to proceed to the left. I. H 2 O(g) H 2 (g) O (g)(remove water) 2 ⇔ 2 + 2 II. H (g) I (g) 2 HI(g)(removeHI) 2 + 2 ⇔ III. CaCO (s) CaO(s) CO (g) (decrease pressure) 3 ⇔ + 2 IV. N (g) O (g) 2 NO(g)(add O ) 2 + 2 ⇔ 2 V. BaO(s) SO (g) BaSO (s) (increase volume) + 3 ⇔ 4 A. I and III B. II and III C. III and IV D. I and V E. II and V

D. I and V

Consider the system below at equilibrium at 200°C. 2 Cl2(g) + 2 H2O(g) 4 HCl(g) + O2(g) ∆H = -184.36 kJ Which response contains all the stresses listed that will result in a shift of the equilibrium so that more HCl (g) is produced when equilibrium is re-established? I. Adding Cl2. II. Raising the temperature at constant pressure. III. Decreasing the volume at constant temperature. IV. Increasing the pressure at constant temperature. V. Removing O2. A. I, II, and III. B. II, IV and V C. III and IV D. I and V E. II and IV

D. I and V

. What is the consequence of heating the following equilibrium system to a higher temperature? 2NH3 (g) ↔ N2 (g) + 3 H2 (g) ΔH° = +92.4 kJ/mol A. The concentration of N2 will decrease, and the equilibrium constant will decrease. B. The concentration of NH3 will decrease, and the equilibrium constant will decrease. C. The concentration of NH3 will increase and the equilibrium constant will increase. D. The concentration of N2 will increase, and the equilibrium constant will increase. E. The concentration of N2 will increase and the equilibrium constant will decrease.

D. The concentration of N2 will increase, and the equilibrium constant will increase.

22. Calculate Kp for the reaction 2NOCl(g) 2NO(g) + Cl2(g) at 400°C if Kc at 400°C for this reaction is 2.1 × 10-2 . A) 2.1 × 10-2 B) 1.7 × 10-3 C) 0.70 D) 3.8 × 10-4 E) 1.2

E) 1.2

A saturated aqueous solution of calcium hydroxide has a pH of 12.25. What is the [Ca2+] of such a solution? A) 0.018 B) 5.6 × 10-13 C) 2.3 × 10-5 D) 0.035 E) 8.9 × 10-3

E) 8.9 × 10-3

For the following reaction: H2CO3 + S2- HCO3 - + HS- the equilibrium constant, K, is greater than one. The stronger acid in this system is ___________ and the weaker base is ____________. A). H2CO3 and HS- B). S2- and HS- C). HCO3 - and S2- D). HS- and S2- E). H2CO3 and HCO3 -

E). H2CO3 and HCO3 -

If kf = 2.3 x 10-2 s-1 and kr = 6.8 x 10-2 s-1 for the general equilibrium reaction A B, then what is the value of Kc? A. 1.6 x 10-3 B. 3.0 C. -4.5 x 10-2 D. 9.1 x 10-2 E. 0.34

E. 0.34

In the coal-gasification process, carbon monoxide is converted to carbon dioxide via the following reaction: CO (g) + H2O (g) CO2 (g) + H2 (g) In an experiment, 0.35 mol of CO and 0.40 mol of H2O were placed in a 1.00-L reaction vessel. At equilibrium, there were 0.19 mol of CO remaining. Kc at the temperature of the experiment is ___________. A. 0.75 B. 1.0 C. 5.47 D. 1.78 E. 0.56

E. 0.56

Which statement is true? A. As the strength of a weak acid increases, the percent dissociation decreases B. As the concentration of a weak acid increases, the percent dissociation increases. C. As the strength of a weak acid decreases, the percent dissociation increases. D. The percent dissociation of a weak acid is independent of the identity of the weak acid. E. As the value of Ka increases, the percent dissociation increases.

E. As the value of Ka increases, the percent dissociation increases.

In which of the following reactions would increasing pressure at constant temperature not change the concentrations of reactants and products, based on Le Chatelier's principle? A. N2 (g) + 3H2 (g) 2NH3 (g) B. 2N2 (g) + O2 (g) 2N2O (g) C. N2 (g) + 2O2 (g) 2NO2 (g) D. N2O4 (g) 2NO2 (g) E. N2 (g) + O2 (g) 2NO (g)

E. N2 (g) + O2 (g) 2NO (g)

. How is the reaction quotient, Q, used to determine whether a system is at equilibrium? A. The reaction is at equilibrium when Q < Keq. B. The reaction is at equilibrium when Q > Keq. C. At equilibrium, the reaction quotient is undefined. D. The reaction quotient must be satisfied for equilibrium to be achieved. E. The reaction is at equilibrium when Q = Keq.

E. The reaction is at equilibrium when Q = Keq.

The concentration of HNO3 in water is gradually increased without changing the volume significantly. Which of the following describes what happens to the concentrations of H3O + and OH- , the pH and the pOH?

e