Deck 12: Chemical Equilibrium

Question 1

If the equilibrium constant of a reaction is greater than zero, it indicates that the reaction tends to favor the forward direction and the formation of products.

Answer 1

True

Question 2

In the context of equilibrium constants of chemical reactions, which "K" value indicates a reaction that favors the formation of products the most?

A)K = 5.31 × 10³
B)K = 4.99 × 10⁶
C)K = 8.2 × 10 ^{− 3}
D)K = 1.7 × 10 ^{− 6}

Answer 2

K = 4.99 × 10⁶

Question 3

Which of the following chemical species is a Brønsted Lowry base?

A)NaOH
B)C₄H₁₀
C)CaCl₂
D)H₂SO₄

Answer 3

NaOH

Question 4

Concrete structures with many small cracks are more likely to fail than similar structures with fewer, larger cracks.

Question 5

In a dynamic equilibrium, _____.

A)the rate of the forward reaction goes to zero
B)the rate of the reverse reaction goes to zero
C)the rates of the forward and reverse reactions become equal
D)the reaction begins to favor the reverse direction

Question 6

Hydrogen is industrially produced by the following reaction between propane and liquid water: ​
C₃H₈( g )+ 3H₂O( l )→ 3CO( g )+ 7H₂( g ).
If the denominator of the equilibrium expression is expressed as [C ₃ H ₈ ] ^m [ H ₂ O] ⁿ , what are the values of "m" and "n"?

A)3 and 7
B)1 and 0
C)1 and 3
D)7 and 3

Question 7

In a dynamic equilibrium, the rates of the forward and reverse reactions go to zero once the equilibrium is reached.

Question 8

The reaction 2A( s )+ B( g ) 2C( s )represents a(n) _____.

A)homogeneous equilibrium
B)heterogeneous equilibrium
C)instantaneous equilibrium
D)reaction that will not come to an equilibrium

Question 9

Which of the following chemical species is a Brønsted-Lowry acid?

A)NaOH
B)C₄H₁₀
C)CaCl₂
D)H₂SO₄

Question 10

"Insoluble" salts are actually "sparingly" soluble at equilibrium conditions.

Question 11

The term "strong acid" refers to any acid of 0.100 M concentration or higher.

Question 12

In the context of exothermic reactions in equilibrium, when the temperature is lowered, heat flows out from the system and the system responds by generating additional heat-moving the equilibrium toward products.

Question 13

If a reaction is in a state where the reaction quotient is more than the equilibrium constant, _____.

A)the rate of the reaction will always double
B)more products will form
C)more reactants will form
D)the reaction will remain in a steady state

Question 14

The higher the K _sp of a salt, the less soluble the salt.

Question 15

The production of ammonia N₂( g )+ 3H₂( g ) 2NH₃( g )represents a(n) _____.

A)homogeneous equilibrium
B)heterogeneous equilibrium
C)instantaneous equilibrium
D)reaction that will not come to an equilibrium

Question 16

According to the Brønsted-Lowry theory of acids and bases, acids are proton (hydronium)acceptors.

Question 17

Unlike traditional concrete, engineered cementitious composites (ECC)do not contain gravel but instead contain fly ash.

Question 18

If NaCl is added to a saturated solution of AgCl, the equilibrium will shift back toward the reactants.

Question 19

A catalyst will increase the rate of the forward and reverse reactions equally.

Question 20

Products appear in the numerator of the reaction quotient.

Question 21

At equilibrium, Δ G  _____.

A)= 0
B)> 0
C)< 0
D)cannot be determined

Question 22

What is the molar solubility of AgCl (K_sp= 1.8 × 10 ^{− 10})?

A)7.31 × 10 ^{− 5}M
B)5.13 × 10 ^{− 6}M
C)3.84 × 10 ^{− 5}M
D)1.34 × 10 ^{− 5}M

Question 23

The conjugate acid of sodium acetate (Na⁺CH₃COO ⁻ )is  _____.

A)NaOH
B)CH₃COOH
C)HCl
D)K⁺CH₃COO ⁻

Question 24

What is the pH of a 0.1055 M CH₃COOH solution (K_a= 1.75 × 10 ^{− 5})?

A)2.770
B)2.867
C)3.188
D)8.474

Question 25

Which of the following is a strong base?

A)HClO₄
B)HNO₂
C)HCl
D)KOH

Question 26

Potassium hydrogen phthalate (KHP)concentrations can be determined through titrating samples of KHP (a monoprotic acid)with bases such as NaOH in the presence of an indicator such as phenolphthalein. The indicator is colorless in an acidic solution and turns pink in an alkaline solution. Thus, we can establish an equilibrium for the phenolphthalein with the following reaction.
HIn + H₂O In ⁻ + H₃O⁺
​
If the HIn species is "acid color" or colorless for the phenolphthalein, and the In ⁻  species is "base color" or pink for this particular indicator, what color will appear in a flask in which a 0.2993 gram sample of KHP is completely neutralized with an excess of NaOH?

A)The flask will be colorless.
B)The flask will be pink.
C)The flask will be white from KCl precipitation.
D)There is insufficient information to solve this problem.

Question 27

The synthesis of the pesticide thionyl chloride (OSCl₂)proceeds according to the following reaction: ​
SO₃( g )+ SCl₂( l ) OSCl₂( l )+ SO₂( g )
​
If Δ G⁰ is − 106 kJ\mol for this reaction at 298K, what is the K_eqat this temperature? Recall that R is 8.314 J mol ^{− 1}K ^{− 1}.

A)7.21 × 10¹²
B)3.50 × 10¹⁴
C)3.81 × 10¹⁸
D)1.19 × 10²⁰

Question 28

The conjugate base of ammonium ion is  _____.

A)NH₃
B)HNO₂
C)HCl
D)HNO₃

Question 29

Which of the following chemical species is amphoteric?

A)NaOH
B)C₄H₁₀
C)H₂O
D)H₂SO₄

Question 30

Consider the following reaction of a weak base with water :
ClO ⁻ + H₂O HClO + OH ⁻
​
If a dilute HCl sample is slowly titrated into a sample of ClO ⁻ , the [ClO ⁻ ] concentration:

A)decreases.
B)remains constant.
C)increases in a linear fashion.
D)increases exponentially.

Question 31

What change in the reaction direction occurs if dilute NaOH is added to a H ₂ PO ₄ ⁻ solution? ​
H₂PO₄ ⁻ + H₂O HPO₄^{2 −} + H₃O⁺
​

A)The reaction shifts to the right.
B)The reaction shifts to the left.
C)There is no change in the reaction.
D)There is insufficient information to solve this problem.

Question 32

Which of the following is a weak acid?

A)NH₃
B)HCN
C)HCl
D)HNO₃

Question 33

What change in reaction direction occurs if dilute HCl is added to a H₂PO₄ ⁻ solution? ​
H₂PO₄ ⁻ + H₂O HPO₄^{2 −} + H₃O⁺
​

A)The reaction shifts to the right.
B)The reaction shifts to the left.
C)There is no change in the reaction.
D)There is insufficient information to solve this problem.

Question 34

What is the molar solubility of CaF₂(K_sp= 3.9 × 10 ^{− 11})?

A)6.24 × 10 ^{− 6}M
B)4.41 × 10 ^{− 6}M
C)2.14 × 10 ^{− 4}M
D)9.27 × 10 ^{− 5}M

Question 35

What is the pH of a 0.150 M NaOH solution?

A)0.82
B)3.05
C)11.66
D)13.18

Question 36

What is the pH of a 0.0250 M pyridine (C ₅ H ₅ N) solution? (K_b= 1.5 × 10 ^{− 9})

A)8.79
B)5.21
C)13.1
D)4.72

Question 37

The lower the pH of a weak acid, the:

A)higher the concentration of the weak acid.
B)higher the dissolved H_2(g)concentration.
C)higher the acid ionization constant of the acid.
D)higher the concentration of its conjugate base.

Question 38

Consider the solubility of BaSO₄. If Ba(NO₃)₂is added to the solution, the solubility of the barium sulfate  _____.

A)is unaffected
B)is unchanged as barium sulfate is a strong electrolyte
C)decreases
D)increases

Question 39

What is the pH of a 0.200 M solution of HNO₃?

A)0.70
B)1.31
C)6.18
D)8.53

Question 40

Which of the following solids will provide the greatest concentration of Cl ⁻ ions if one mole of salt is placed in one liter of deionized water?

A)AgCl( s ) Ag¹⁺( aq )+ Cl^{1 −} ( aq )K_sp= 1.8 × 10 ^{− 10}
B)NH ₄ Cl ( s )  NH ₄ ⁺ ( aq )+ Cl ^{1 −} ( aq )K _sp = 30.9
C)Hg₂Cl₂( s ) 2Hg¹⁺( aq )+ 2Cl^{1 −} ( aq )K_sp= 1.1 × 10 ^{− 18}
D)NaCl( s )→ Na ¹⁺ ( aq )+ Cl ^{1 −} ( aq )K _sp = 36

Question 41

According to LeChatelier's principle, when a system at equilibrium is stressed, it responds by reestablishing equilibrium to reduce the applied stress.

Question 42

In any chemical system at equilibrium, the rate of the forward reaction equals the rate of the reverse reaction.

Question 43

Consider the following reaction:
SO₃( g )+ CaO( s )  CaSO₄( s ).
If Δ G ⁰ is − 345 kJ\mol for this reaction at 298K, what is the K _eq at this temperature? Recall that R is 8.314 J mol ^{− 1} K ^{− 1} .

A)3.1 × 10 ⁴⁰
B)3.50 × 10 ⁵⁰
C)2.96 × 10 ⁶⁰
D)2.23 × 10 ⁷⁰

Question 44

In heterogeneous equilibria, reactants and products are all in the same phase.

Question 45

According to LeChatelier's principle, when the reaction quotient is less than the equilibrium constant of a reaction, the reaction:

A)must shift toward products to reach equilibrium.
B)must shift toward reactants to reach equilibrium.
C)results in an increase in standard enthalpy of formation of reactants.
D)results in an increase in standard enthalpy of formation of products.