QUESTION 1

Which pair of compounds will form a buffer in aqueoussolution?

	a.	HCN and NaCN
	b.	NaCN and NaOH
	c.	HCl and NaOH
	d.	HCl and NaCl
	e.	HCN and HCl
	f.	NaCN and KCN

10 points   

QUESTION 2

A buffer solution is titrated with 0.032 M HCl solution. Theinitial volume of the buffer is 25.00 mL. The equivalence point ofthe titration is determined to be 4.88 mL. What is theconcentration of conjugate base (in M) in the buffer solution?Assume the stoichiometry of acid to base is 1:1.

10 points   

QUESTION 3

A buffer solution is titrated with 0.046 M NaOH solution. Theinitial volume of the buffer is 25.00 mL. The equivalence point ofthe titration is determined to be 8.77 mL. What is theconcentration of acid (in M) in the buffer solution? Assume thestoichiometry of acid to base is 1:1.

10 points   

QUESTION 4

The concentrations of acid and conjugate base in a buffer aredetermined experimentally to be 0.044 M and 0.059 M, respectively.If the total buffer concentration given on the bottle (the truevalue) is 0.102 M, then what is the percent error of theexperimental value?

10 points   

QUESTION 5

There are several calculations that need to be done in order toprepare a specific volume of buffer solution at a particularconcentration and pH. There is a worked example in your lab manualon p. 119.

First, determine the correct A^-/HAratio:  The pK_a of acetic acid is 4.76, andthe buffer solution needs to maintain a pH of 4.25. Theconcentration of acetate (CH₃CO₂^-)should be X times that of the concentration ofacetic acid (CH₃CO₂H). What isX?

10 points   

QUESTION 6

There are several calculations that need to be done in order toprepare a specific volume of buffer solution at a particularconcentration and pH. There is a worked example in your lab manualon p. 119.

Once the correct ratio of A^- to HA is known,determine the actual concentration of A- needed to make a buffer ata particular concentration.

The ratio of acetate to acetic acid in a buffer is 0.176. Thatis, the concentration of acetate should be 0.176 times that of theconcentration of acetic acid. What is the concentration of acetate(in M) needed to prepare a 0.416 M buffer using acetic acid andacetate?

10 points   

QUESTION 7

There are several calculations that need to be done in order toprepare a specific volume of buffer solution at a particularconcentration and pH. There is a worked example in your lab manualon p. 119.

What volume of acetate solution (in mL) is needed to make 250.0mL of a buffer solution? The concentration of acetate in the buffermust be 0.0594 M, and the concentration of the acetate stocksolution is 0.500 M.