Question

1)

A 1.0-L buffer solution is 0.125 M in HNO2 and 0.180 M in NaNO2.

Part A

Determine the concentrations of HNO2 and NaNO2 after addition of 1.5 g HCl.

Express your answers using three significant figures separated by a comma.

Part B

Determine the concentrations of HNO2 and NaNO2 after addition of 1.5 g NaOH.

Express your answers using three significant figures separated by a comma.

Part C

Determine the concentrations of HNO2 and NaNO2 after addition of 1.5 g HI.

Express your answers using three significant figures separated by a comma.

2)

A 1.0 L buffer solution is 0.250 M HC2H3O2 and 0.050 M LiC2H3O2. Which of the following actions will destroy the buffer?

A 1.0 L buffer solution is 0.250 M HC2H3O2 and 0.050 M LiC2H3O2. Which of the following actions will destroy the buffer?

	adding 0.050 moles of LiC2H3O2
	adding 0.050 moles of NaOH
	adding 0.050 moles of HC2H3O2
	adding 0.050 moles of HCl
	None of the above will destroy the buffer. 3) Part A Write a balanced equation for the dissolution of CaCO3. Express your answer as a chemical equation. Identify all of the phases in your answer. Part B Write an expression for Ksp for the dissolution of CaCO3. Write an expression for  for the dissolution of . Ksp=[CO2−3][CaCO3] Ksp=[Ca2+][CO2−3]2 Ksp=[Ca2+][CaCO3] Ksp=[CaCO3][Ca2+][CO2−3] Ksp=[Ca2+][CO2−3] Ksp=[Ca2+]2[CO2−3] Ksp=[Ca2+][CO2−3][CaCO3] Part C Write a balanced equation for the dissolution of PbCl2. Express your answer as a chemical equation. Identify all of the phases in your answer. Part D Write an expression for Ksp for the dissolution of PbCl2. Write an expression for  for the dissolution of . Ksp=[Pb2+][Cl−]2 Ksp=[Pb2+][Cl−] Ksp=[Pb2+]2[Cl−] Ksp=[PbCl2][Pb2+][Cl−]2 Ksp=[Pb2+][Cl−]2[PbCl2] Ksp=[Pb2+][PbCl2] Ksp=[Cl−]2[PbCl2] Part E Write a balanced equation for the dissolution of AgI. Express your answer as a chemical equation. Identify all of the phases in your answer. Part F Write an expression for Ksp for the dissolution of AgI. Write an expression for  for the dissolution of . Ksp=[AgI][Ag+][I−] Ksp=[Ag+][I−]2 Ksp=[Ag+][AgI] Ksp=[Ag+]2[I−] Ksp=[Ag+][I−][AgI] Ksp=[I−][AgI] Ksp=[Ag+][I−] 4) A ligand is a molecule or ion that acts as a A ligand is a molecule or ion that acts as a Lewis acid Arrhenius base conjugate base Brønsted-Lowry base Lewis base 5) A buffer contains significant amounts of acetic acid and sodium acetate. Part A Write an equation showing how this buffer neutralizes added acid (HCl). Express your answer as a chemical equation. Part B Write an equation showing how this buffer neutralizes added base (Ca(OH)2). Express your answer as a chemical equation. 6) When titrating a monoprotic strong acid with a weak base at 25°C, the When titrating a monoprotic strong acid with a weak base at 25°C, the pH will be 7 at the equivalence point. titration will require more moles of the base than acid to reach the equivalence point. pH will be less than 7 at the equivalence point. titration will require more moles of acid than base to reach the equivalence point. pH will be greater than 7 at the equivalence point.

Answer 1

1) Let us find the intial moles of HNO2 and NaNO2

moles of HNO2 = M x L = 0.125 x 1 = 0.125 mols

moles of NaNO2 = 0.180 x 1 = 0.180 mols

Part A) added 1.5 g of HCl

mols of HCl = g/molar mass = 1.5/36 = 0.0417 mols

So, new mols of HNO2 and NaNO2 in solution,

mols of HNO2 = 0.125 + 0.0417 = 0.1667 mols

mols of NaNO2 = 0.180 - 0.0417 = 0.1383 mols

Concentration of HNO2 = 0.1667/1 = 0.1667 M

Concentration of NaNO2 = 0.1383/1 = 0.1383 M

Part B) added 1.5 g of NaOH

mols of NaOH = g/molar mass = 1.5/40 = 0.0375 mols

So, new mols of HNO2 and NaNO2 in solution,

mols of HNO2 = 0.125 - 0.0375 = 0.0875 mols

mols of NaNO2 = 0.180 + 0.0375 = 0.2175 mols

Concentration of HNO2 = 0.0875/1 = 0.0875 M

Concentration of NaNO2 = 0.2175/1 = 0.2175 M

Part C) added 1.5 g of HI

mols of Hl = g/molar mass = 1.5/128 = 0.01172 mols

So, new mols of HNO2 and NaNO2 in solution,

mols of HNO2 = 0.125 + 0.01172 = 0.1367 mols

mols of NaNO2 = 0.180 - 0.01172 = 0.1683 mols

Concentration of HNO2 = 0.1367/1 = 0.1367 M

Concentration of NaNO2 = 0.1683/1 = 0.1683 M

2) adding 0.050 moles of HCl

will destroy the buffer.HCl is a strong acid as opposed to the acid present to prepare the buffer in solution.

3) Dissolution of CaCO3

Overall equation

CaCO3(s) + 2 H+(aq) ---> Ca++(aq) + H2O(aq) + CO2(g)

Breakdown of above equation,

CaCO3(s) + H+(aq) ---> Ca++(aq) + HCO3-(aq)

HCO3-(aq) + H+(aq) ---> H2O(aq) + CO2(g)

Part B) Ksp espression of CaCO3

Ksp=[Ca2+][CO2−3]

Part C) Dissolution of PbCl2

PbCl2(s) + H2O(l) ---> Pb^2+(aq) + 2Cl-(aq)

Part D) Ksp expression for PbCl2

Ksp=[Pb2+][Cl−]2

Part E) Dissolution of AgI

AgI(s) + H2O(l) <===> Ag+(aq) + I-(aq)

Part F) Ksp expression of AgI

Ksp=[Ag+][I−]

4) A ligand is a molecule or ion that acts as a

Lewis base

5) The buffer is acetic acid CH3COOH and sodium acetate CH3COONa

Part A) With HCl

Acetic Acid: CH3COOH
Sodium Acetate : CH3COONa

CH3COOH + H2O <===> CH3COO + H3O+

acetate will react with the H in HCl following the reaction, to convert it to the weak acetic acid to minimize pH changes

CH3COO + H --> CH3COOH

Part B) With Ca(OH)2
the acetic acid will react with the OH:

2CH3COOH + Ca(OH)2 --> (CH3COO)2Ca + 2H2O

6) When titrating a monoprotic strong acid with a weak base at 25°C, the

pH will be less than 7 at the equivalence point