Which one of the following combinations will give a buffer solution? a. 50 ml 1.

Question

Which one of the following combinations will give a buffer solution?

a. 50 ml 1.0 M HCl and 100 ml 1.0 M HOAc

b. 80 ml 1.0 M NaOH and 100 ml 1.0 M HOAc

c. 100 ml 1.0 M HCl and 80 ml 1.0 M HOAc

d. 50 ml 1.0 M NaOH and 100 ml 1.0 M NaOAc

e. 50 ml 1.0 M HCl and 50 ml 1.0 M NaOAc

the answer is b can you explain why?

9. Your T.A. gives you a solution that might contain Ba2+, Fe3+, Ag+ , and Ni2+. Which reagents should you use to separate these ions, and in what order?

a. First add NaCl, then Na2SO4, then 1.0 M NH3, then 15 M NH3

b. First add 1.0 M NH3, then HNO3, then Na2SO4, then 1.0 M NaOH

c. First add 15 M NH3, then NaOH, then HNO3, then Na2SO4

d. First add NaCl, then HNO3, then 1.0 M NH3, then Na2SO4

answer is A why? how?

thx!

Explanation / Answer

A buffered solution is one that resists a change in its pH when either hydroxide ions or protons are added. A buffered solution may contain a weak acid and its salt or weak base and its salt.

b. 80 ml 1.0 M NaOH and 100 ml 1.0 M HOAc

in this mixture HOAc is weak acid which react with NaOH and from ACo- ; conjugated base.

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