34 6.6 Buffers

Practice questions

1. Is this statement true? A buffer is the combination of a weak acid or base and a salt of that weak acid or base.
2. Which combinations of compounds can make a buffer? Assume aqueous solutions. Select all possible answers.
   
   1. 1. [latex]\ce{HCl}[/latex] and [latex]\ce{NaCl}[/latex]
      2. [latex]\ce{NH_{4}NO_{3}}[/latex] and [latex]\ce{NH_{3}}[/latex]
      3. [latex]\ce{HNO_{2}}[/latex] and [latex]\ce{NaNO_{2}}[/latex]
      4. [latex]\ce{NH_{4}NO_{3}}[/latex] and [latex]\ce{HNO_{3}}[/latex]
3. The complete phosphate buffer system is based on four substances: [latex]\ce{H_{3}PO_{4}}[/latex], [latex]\ce{H_{2}PO_{4}^{-}}[/latex], [latex]\ce{HPO_{4}^{2-}}[/latex], and [latex]\ce{PO_{4}^{3-}}[/latex].  What different buffer solutions can be made from these substances?
   1. 1. [latex]\ce{H_{3}PO_{4}}[/latex] and [latex]\ce{H_{2}PO_{4}^{-}}[/latex]
      2. [latex]\ce{H_{2}PO_{4}^{-}}[/latex] and [latex]\ce{HPO_{4}^{2-}}[/latex]
      3. [latex]\ce{HPO_{4}^{2-}}[/latex] and [latex]\ce{PO_{4}^{3-}}[/latex]
      4. All of the above

Answers

1. True
2. b, c
3. d