Question

1)

How many grams of dry NH4Cl need to be added to 2.30 L of a 0.100 M solution of ammonia, NH3, to prepare a buffer solution that has a pH of 8.64? Kb for ammonia is 1.8×10−5.

Express your answer with the appropriate units.

2)

Part A

a solution that is 0.175 M in HC2H3O2 and 0.120 M in KC2H3O2

Express your answer using two decimal places.

PH=

Part B

a solution that is 0.195 M in CH3NH2 and 0.110 M in CH3NH3Br

Express your answer using two decimal places.

PH=

3)

A buffer contains significant amounts of ammonia and ammonium chloride.

Part A

Write an equation showing how this buffer neutralizes added acid (HNO3).

Express your answer as a chemical equation.

Part B

Write an equation showing how this buffer neutralizes added base (CsOH).

Express your answer as a chemical equation.

4)

Calculate the ratio of CH3NH2 to CH3NH3Cl required to create a buffer with pH = 10.20.

Express your answer using two significant figures.

5)

Buffer capacity depends on two quantities. What are they?

a high concentration of conjugate acid molecules in solution and the pH of the solution

an equal number of conjugate acid and base molecules, and a high concentration of each

how close the buffer is to having a 10:1 ratio of the buffer components, and having a high concentration of the components

the range of pH values over which the solution can act as a buffer, and an equal ratio of conjugate acid to conjugate base

6)

A 1.0-L buffer solution is 0.120 M in HNO2 and 0.160 M in NaNO2.

Part A

Determine the concentrations of HNO2 and NaNO2 after addition of 1.7 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 1.7 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 1.7 g HI.

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

7)

Why is the molar solubility of silver chloride lower in an aqueous solution of sodium chloride than in pure water?

Why is the molar solubility of silver chloride lower in an aqueous solution of sodium chloride than in pure water?

because the presence of extra chloride ion shifts the equilibrium of the AgCl dissolution reaction toward the undissociated silver chloride

because solubility relies on concentrations of all the species in the dissolution reaction equation, and lower solubility means higher amounts of solid silver chloride

because silver ions and sodium ions form a completely insoluble precipitate and fall out of the solution

because sodium chloride takes up all the water and doesn't leave any interactions for the silver chloride, causing reduced solubility

8)

In which of the following would lead sulfate be most soluble?

In which of the following would lead sulfate be most soluble?

	1 M NaNO3
	1 M H2SO4
	1 M Pb(NO3)2
	1 M CuSO4