Deck 12: Chemical Equilibrium

Question 1

A large "K" value (>0) indicates that the reaction tends to favor the forward direction and the formation of products.

Answer 1

True

Question 2

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

Answer 2

False

Question 3

Exothermic reactions in equilibrium will favor the reactants if the system is cooled.

Answer 3

False

Question 4

Which of following species is a Brønsted-Lowry base?

A) NaOH
B) C₄H₁₀
C) CaCl₂
D) H₂SO₄

Question 5

If NaCl is added to a saturated solution of AgCl, the equilibrium will shift back towards the reactants; and the solubility of AgCl will decrease.

Question 6

Which "K" value indicates a reaction most favoring the formation of products?

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

Question 7

Which of following species is a Brønsted-Lowry acid?

A) NaOH
B) C₄H₁₀
C) CaCl₂
D) H₂SO₄

Question 8

If a reaction is in a state where Q > K,

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 9

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

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

Question 10

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

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

Question 11

The higher the K_sp of the salt, the less soluble the salt.

Question 12

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

Question 13

Products appear in the numerator of the reaction quotient

Question 14

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

Question 15

In a dynamic equilibrium:

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

Question 16

Hydrogen is produced industrially by reacting propane and liquid water:
C₃H₈( g ) + 3 H₂O( l ) → 3 CO( g ) + 7 H₂( g )
If the denominator of the equilibrium expression is expressed as: [C₃H₈]^m[ H₂O]ⁿ, what are the values of "m" and "n"?

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

Question 17

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

Question 18

"Insoluble" salts are actually "sparingly" soluble with equilibrium expressions noted as K_a

Question 19

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

Question 20

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

Question 21

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

A) NaOH
B) CH₃COOH
C) HCl
D) K⁺CH₃COO ⁻

Question 22

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

A) decreases
B) remains constant
C) increases
D) there is insufficient information to solve this problem

Question 23

What change in reaction direction occurs if dilute HCl is added to a H₂PO₄ ⁻ solution?
H₂PO₄ ¹⁻ + H₂O HPO₄^{2 −} + H₃O⁺

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

Question 24

What is the pH of a 0.150 M NaOH solution?

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

Question 25

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

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

Question 26

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 27

Which of the following is a strong base?

A) HClO₄
B) HNO₂
C) HCl
D) KOH

Question 28

What change in the reaction direction occurs if dilute NaOH is added to a H₂PO₄^1- solution?
H₂PO₄ ¹⁻ + H₂O HPO₄^{2 −} + H₃O⁺

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

Question 29

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 30

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

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

Question 31

Which of the following is a weak acid?

A) NH₃
B) HClO
C) HCl
D) HNO₃

Question 32

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

A) is unaffected
B) is moot because barium sulfate is a strong electrolyte
C) decreases
D) increases

Question 33

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 as such:
HIn + H₂O In ⁻ + H₃O⁺
If the HIn species is the "acid color" or clear for the phenolphthalein and the In ⁻ species is the "base color" or pink for this particular indicator, what color will appear in a flask in which a 0.2993 gram sample of KHP has been totaled neutralized with an excess of NaOH?

A) the flask is colorless
B) the flask is pink
C) the flask is white from KCl precipitation
D) there is insufficient information to solve this problem

Question 34

Which of the following solids will provide the greatest concentration of Cl^{1 −} ions if one mole of the salt is placed in one liter of deionized water?

A) AgCl( s ) Ag¹⁺( aq ) + Cl^{1 −} ( aq ) K_sp = 1.8 × 10 ^{− 10}
B) PbCl₂( s ) Pb²⁺( aq ) + 2 Cl^{1 −} ( aq ) K_sp = 1.75 × 10 ^{− 5}
C) Hg₂Cl₂( s ) 2 Hg¹⁺( aq ) + 2 Cl^{1 −} ( aq ) K_sp = 1.1 × 10 ^{− 18}
D) NaCl( s ) → Na¹⁺( aq ) + Cl^{1 −} ( aq )

Question 35

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 36

Which of following species is amphoteric?

A) NaOH
B) C₄H₁₀
C) H₂O
D) H₂SO₄

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 K_a of the acid.
D) none of the above

Question 38

The conjugate base of ammonium chloride is:

A) NH₃
B) HNO₂
C) HCl
D) HNO₃

Question 39

At equilibrium Δ G is:

A) = 0
B) > 0
C) can not be determined

Question 40

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