# Aqueous Ionic Equilibrium 2

Aqueous Ionic Equilibrium 2

1- Which of the following processes will result in an increase of entropy of the system? Choose from:

2- What does the standard change in Gibbs free energy ( ) of a reaction tell us about the equilibrium constant (K) for that reaction under standard conditions? Choose from:

There is no significant relationship between and K.

A negative indicates that product formation is favored, and K will be greater than 1.

A negative indicates that reactant formation is favored, and K will be less than 1.

3- Which of the following combinations of and describe a process that is only spontaneous at low temperatures? Choose from:

: positive , : positive

: negative , : positive

: positive , : negative

: negative , : negative

Spontaneity is not related to the sign of and .

4- AB 2 has a molar solubility of 3.72Ã—10 âˆ’4 M . What is the value of the solubility product constant for AB2 ?

5- C 2 D 3 has a solubility product constant of 9.14Ã—10 âˆ’9 . What is the molar solubility of C 2 D 3 ?

6- A buffer contains significant amounts of ammonia and ammonium chloride.

Part A:Write an equation showing how this buffer neutralizes added acid (HI)

Part B: Write an equation showing how this buffer neutralizes added base (CsOH). Express your answer as a chemical equation.

7- Solve an equilibrium problem (using an ICE table) to calculate the pH of each solution:

Part A: a solution that is 0.165M in HC 2 H 3 O 2 and 0.120M in KC 2 H 3 O 2

Part B: a solution that is 0.185M in CH 3 NH 2 and 0.110M in CH 3 NH 3 Br

8- A 1.0-L buffer solution is 0.105M in HNO 2 and 0.145M in NaNO 2 . Express your answers using three significant figures separated by a comma.

Part A: Determine the concentrations of HNO 2 and NaNO 2 after addition of 1.4g HCl

Part B: Determine the concentrations of HNO 2 and NaNO 2 after addition of 1.4g NaOH .

Part C: Determine the concentrations of HNO 2 and NaNO 2 after addition of 1.4g HI.

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## SOLUTION This solution is **FREE** courtesy of BrainMass!

Aqueous Ionic Equilibrium 2

1- Which of the following processes will result in an increase of entropy of the system? Choose from:

Entropy will increase when moles of gas increases like when 2 moles of NH3 forms a total of 4 moles of gaseous products N2 and H2.

2- What does the standard change in Gibbs free energy ( ) of a reaction tell us about the equilibrium constant (K) for that reaction under standard conditions? Choose from:

There is no significant relationship between and K.

A negative indicates that product formation is favored, and K will be greater than 1.

A negative indicates that reactant formation is favored, and K will be less than 1.

A reaction will be spontaneous when dG is negative. Hence product formation is favored and K must be greater than 1.

3- Which of the following combinations of and describe a process that is only spontaneous at low temperatures? Choose from:

: positive , : positive

: negative , : positive

: positive , : negative

: negative , : negative

Spontaneity is not related to the sign of and .

dG = dH - TdS

For spontaneity only at low T, dH must be negative and dS negative.

4- AB 2 has a molar solubility of 3.72Ã—10 âˆ’4 M . What is the value of the solubility product constant for AB2 ?

AB2 --ïƒ A2+ + 2B-

Ksp = (s)(2s)^2 = 4s^3

Ksp =4 (3.72 x 10-4)3 = 2.06 x 10-10

5- C 2 D 3 has a solubility product constant of 9.14Ã—10 âˆ’9 . What is the molar solubility of C 2 D 3 ?

C2D3 --ïƒ 2C3+ + 3D2-

Ksp = (2s)2(3s)3 = 108s5

9.14 x 10-9 = 108 s5

Hence s= 0.00967 M

6- A buffer contains significant amounts of ammonia and ammonium chloride.

Part A:Write an equation showing how this buffer neutralizes added acid (HI)

HI + NH3 --ïƒ NH4+

Part B: Write an equation showing how this buffer neutralizes added base (CsOH). Express your answer as a chemical equation.

NH4+ + Cl - + CsOH --ïƒ NH3 + Cs+ + Cl- + H2O

7- Solve an equilibrium problem (using an ICE table) to calculate the pH of each solution:

Part A: a solution that is 0.165M in HC 2 H 3 O 2 and 0.120M in KC 2 H 3 O 2

C2H3O2 - + H2O --ïƒ HC2H3O2 + OH-

Initial 0.165 0.120

Change -x +x +x

Eqbm 0.165-x 0.120+x x

Kb = 5.56x10-10 = (0.120)(x) / 0.165 approximating 'x' to be really small

Solving gives x = 7.64 x 10-10

pOH = 9.12

Hence pH = 4.88

Part B: a solution that is 0.185M in CH 3 NH 2 and 0.110M in CH 3 NH 3 Br

CH3NH3+ --ïƒ CH3NH2 + H+

Initial 0.110 0.185

Change -x +x +x

Eqbm 0.110-x 0.185+x x

Ka = 2..27x10-11 = (0.185)(x) / 0.110 approximating 'x' to be really small

Solving gives x = 1.35x 10-11

Hence pH = 10.87

8- A 1.0-L buffer solution is 0.105M in HNO 2 and 0.145M in NaNO 2 . Express your answers using three significant figures separated by a comma.

Part A: Determine the concentrations of HNO 2 and NaNO 2 after addition of 1.4g HCl

1.4g HCl = 1.4/ 36.46 = 0.0384 mol

HCl will react with NaNO2 to form HNO2 thus increasing HNO2 while decreasing NaNO2

pH = pKa + log [NO2-]/[HNO2]

pH = 3.40 + log[0.145 - 0.0384]/[0.105 + 0.0384]

pH = 3.27

Part B: Determine the concentrations of HNO 2 and NaNO 2 after addition of 1.4g NaOH .

1.4g NaOH= 1.4/ 39.997 = 0.035mol

NaOH will react with HNO2 to form NO2- thus increasing NO2- while decreasing HNO2

pH = pKa + log [NO2-]/[HNO2]

pH = 3.40 + log[0.145 + 0.035]/[0.105 - 0.035]

pH = 3.81

Part C: Determine the concentrations of HNO 2 and NaNO 2 after addition of 1.4g HI.

1.4g HI= 1.4/ 127.91 = 0.0109mol

Addition of HI will increase the HNO2 concentration and decrease NO2-

pH = pKa + log [NO2-]/[HNO2]

pH = 3.40 + log[0.145 - 0.0109]/[0.105 + 0.0109 ]

pH = 3.46

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