Deck 9: Activity and the Systematic Treatment of Equilibrium

Question 1

Calculate the ionic strength of a 0.210 M FeCl₂ solution.

Answer 1

0.630

Question 2

Which equation is NOT required to determine the pH of 0.10 M solution of weak acid,HA?

A)HA + H₂O ⇋ A⁻ + H₃O⁺ K_a = 2.4 × 10⁻⁶
B)H₂O + H₂O ⇋ H₃O⁺ + OH⁻ K_w = 1 × 10⁻¹⁴
C)0)10 = [HA] + [A⁻]
D)[H₃O⁺] = [OH⁻] + [A⁻]
E)A⁻ + H₂O ⇋ HA + OH⁻ K_b = 4.2 × 10⁻⁹

Answer 2

A⁻ + H₂O ⇋ HA + OH⁻ K_b = 4.2 × 10⁻⁹

Question 3

Calculate the pH of a 0.002 M (CH₃)₃N solution.K_b = 6.6 × 10⁻⁵

Answer 3

10.62

Question 4

Calculate the pH of a 0.040 M HCl solution that is also 0.010 M in NaNO₃.

Question 5

For Ag⁺ when  = 0.01 M, = 0.898 and when  = 0.05, = 0.80.What is the activity coefficient when  = 0.024 M?

A)0)804
B)0)845
C)0)853
D)0)864
E)0)894

Question 6

The mass balance equation for a 0.10 M HO₂CCO₂H solution is which of the following?

A)
B)
C)
D)
E)

Question 7

A buffer is prepared from NaH₂PO₄ and Na₂HPO₄.The charge balance equation for the buffer is which of the following?

A)
B)
C)
D)
E)

Question 8

Which equation is NOT required to determine the molar solubility of AgCN?

A)AgCN ⇋ Ag⁺ + CN⁻____________________K_sp = 2.2 × 10⁻¹⁶
B)H₂O + H₂O ⇋ H₃O⁺ + OH⁻ K_w = 1 × 10⁻¹⁴
C)[Ag⁺] = [CN⁻] + [HCN]
D)CN⁻ + H₂O ⇋ HCN + OH⁻ K_b = 1.6 × 10⁻⁵
E)HCN + H₂O ⇋ CN⁻ + H₃O⁺ K_a = 6.2 × 10⁻¹⁰

Question 9

What is the ionic strength of a 2:1 electrolyte with a concentration of 0.100 M?

A)0)100
B)0)200
C)0)300
D)0)400
E)0)500

Question 10

Which of the following is NOT true for pH?

A)pH = −log[H⁺]_H+.
B)pH = −log[H⁺] when  = 0.
C)The pH = pOH for pure water.
D)As ionic strength increases,so does the pH of pure water.
E)The ionic strength of pure water is 1.0 x 10⁻⁷ M.

Question 11

Calculate the activity coefficient for Fe²⁺ for an ionic strength of 0.034 M.For  = 0.01 M, = 0.675 and for  = 0.05 M, = 0.485.

Question 12

____________________ is a measure of the total concentration of ions in solution.

A)Ionic radius
B)Ionic density
C)Ionic degree
D)Ionic strength
E)Ionic atmosphere

Question 13

Calculate the pOH of a 0.010 M HCl solution with an ionic strength of 0.10 M._H+ = 0.83,_OH− = 0.76.

A)11.92
B)11.80
C)11.88
D)12.00
E)12.20

Question 14

Which statement below is INCORRECT for the increased solubility of a sparingly soluble salt,AgCl,in an inert salt solution,NaNO₃?

A)The ionic atmosphere around the silver cations becomes increasingly negative as the nitrate anions are attracted to the silver cations.
B)The ionic strength around the chloride anions becomes increasingly positive as the sodium cations are attracted to the chloride anions.
C)The ionic atmosphere increases the attraction between silver cations and chloride anions,increasing solubility by creating more AgCl (aq)in solution.
D)Ions continually diffuse into and out of the ionic atmosphere.
E)The negative ionic atmosphere around silver cations results in an overall positive charge less than the positive charge of the silver cations.

Question 15

To correct for the effect of ionic strength on chemical reactions,concentrations are replaced by____________________ in equilibrium expressions.

A)activity coefficients
B)ion activities
C)molecular activities
D)activities
E)active strength

Question 16

Calculate the pH of a 0.001 M HCN solution.K_a = 6.2 × 10⁻¹⁰

Question 17

Calculate the pH of a 0.010 M CH₃CO₂H solution.K_a = 1.8 × 10−⁵ for acetic acid.

A)9)26
B)3)39
C)2)02
D)10.61
E)4)74

Question 18

Which statement below is NOT correct for the pH of a 0.01 M NaCl solution versus the pH of a 0.01 M in FeSO₄ solution?

A)The activity coefficient for H⁺ will be larger in 0.01 M NaCl than in 0.01 M FeSO₄.
B)The activity coefficient for OH⁻ will be larger in 0.01 M NaCl than in 0.01 M FeSO₄.
C)The hydronium concentration in 0.01 M NaCl will equal the hydronium concentration in 0.01 M FeSO₄.
D)The H⁺ activity in 0.01 M NaCl will not equal the H⁺ activity in 0.01 M FeSO₄.
E)The OH⁻ activity in 0.01 M NaCl will not equal the OH⁻ activity in 0.01 M FeSO₄.

Question 19

All of the following are TRUE for activities and activity coefficients,except:

A)activity for a chemical species is the product of concentration and activity coefficient.
B)the activity coefficient corrects for non-ideal behavior due to ionic strength.
C)as ionic strength increases,the value of the activity coefficient increases.
D)for ions,the activity coefficient approaches unity as the ionic strength approaches 0.
E)the activity coefficient for neutral molecules is approximately unity when the ionic strength is less than 0.1 M.

Question 20

Which of the statements below are INCORRECT for mass balance and charge balance?
I The mass balance is a statement of the conservation of matter.
II Mass balance is satisfied when the quantity of all species in a solution containing a particular atom (or group of atoms)equals the amount of that atom (or group)reacted.
III The sum of the positive charges in solution equals the sum of the negative charges in solution.
IV The coefficient in front of each species in a charge balance always equals the magnitude of the charge on the counter ion.

A)I,II,III and IV
B)I,III and IV
C)I,II and III
D)I and IV
E)II and III