AP CHEM Unit 7 Day 4 REVIEW

A strong acid is added to a buffer with a pH of 4. Which component of the buffer will help minimize any pH change caused by the added acid?
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• H₂O
• HA
• A^-
• H₃O⁺

Which pair is the most effective buffer?
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• 0.5 M HIO and 0.5 M NaIO
• 0.1 M HF and 0.9 M NaF
• 0.9 M HIO and 0.1 M NaIO
• 0.1 M HF and 0.7 M NaF

Which of the following will NOT make a buffer?
CH₃NH₂ is a weak base.
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• 105.0 mL of 0.15 M CH₃NH₂;
  95.0 mL of 0.10 M HCl
• 125.0 mL of 0.15 M CH₃NH₂;
  120.0 mL of 0.25 M CH₃NH₃Cl
• 165.0 mL of 0.10 M HF;
  135.0 mL of 0.050 M KOH
• 150.0 mL of 0.10 M HClO;
  135.0 mL of 0.075 M HCl

In which solution is the pKa most similar to the pH?
HA is a weak acid in all answer choices.
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• 0.10 mol of HA and 0.11 mol of A- in 1 L of solution
• 0.33 mol of HA and 0.67 mol of A- in 1 L of solution
• 0.10 mol of HA and 0.025 mol of Ba(OH)₂ in 1 L of solution
• 0.10 mol of HA and 0.033 mol of NaOH in 1 L of solution

Which combination is the best choice to prepare a buffer with a pH of 5?
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• CH₃NH₂ (pK_b=3.36);
  CH₃NH₃Cl
• HCHO₂ (pK_a=3.74);
  NaCHO₂
• C₅N₅N (pK_b=8.76);
  C₅H₅NHCl
• HClO (pK_a=7.53);
  NaClO

What is the pH of a buffer that is 0.08 M NaA and 0.1 HA.
The K_a of HA = 1.0 x 10^-4.
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• 2.00
• 3.90
• 4.00
• 4.10

Determine the pH of a solution that results upon mixing 100.0 mL of 0.20 M of a weak acid and 100.0 mL of 0.10 M sodium hydroxide.  
This weak acid is monoprotic and has a K_a=1.0x10^-4.
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• 3.83
• 4.00
• 4.18
• 5.51

Blood is a buffer system between carbonic acid and hydrogen carbonate ions. While the pH of blood is 7.4, the pKa of carbonic acid is 6.1. Why is this beneficial to our survival?
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• [H₂CO₃] < [HCO₃^-] which makes the buffering capacity greater for an acid, enabling our blood to buffer the lactic acid produced while exercising
• [H₂CO₃] < [HCO₃^-] which makes the buffering capacity greater for a base, enabling our blood to buffer the basic effects of low carbon dioxide levels produced from hyperventilation
• [H₂CO₃] > [HCO₃^-] which makes the buffering capacity greater for an acid, enabling our blood to buffer the uric acid produced when cells break down
• [H₂CO₃] > [HCO₃^-] which makes the buffering capacity greater for a base, preventing calcium from binding to blood transport proteins like albumin

Which of the following combinations of equimolar substances could make a buffer?
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• HNO₂ and NaNO₃
• HCl and NaCl
• NH₄Cl and NH₃
• NaOH and HCl

You are asked to make 1.00L of a solution buffered at a pH of 9.00.  You are given 1.00M HCN(K_a = 6.2x10⁻¹⁰) and 1.00M NaCN.  Which of the following statements correctly describes the relative volumes of each solution to make such a buffer?
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• The volumes of the 1.00M HCN and 1.00M NaCN are equal.
• The volume of the 1.00M HCN must be less than the volume of the 1.00M NaCN.
• The volume of the 1.00M HCN must be greater than the volume of the 1.00M NaCN.
• There is no way to make a buffer solution at pH of 9.00 with HCN and NaCN.