1.3 What would you use to prepare a buffer system with a pH of around 4.2. What
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Question
1.3 What would you use to prepare a buffer system with a pH of around 4.2. What would you use to make a buffer with a pH of around 9.2? Describe the process you used to choose the correct buffer for each pH.1.4 A buffer is made by mixing NH4Cl and NH3. Which is the acid component and which is the base component? What is the Ka and pKa for this buffer?
1.5 A buffer is made by mixing 0.30 moles of propanoic acid, C H 3 C H 2 COOH , and 0.20 moles of sodium propanoate, CH 3 CH 2 COO^- N a + . What will the pH of the solution be?
1.6 For the solution in question 5, show the reaction that takes place when a strong acid , HCl, is added to the solution. Show the reaction that takes place when a strong base, NaOH, is added to the solution.
1.7 When a strong acid is added to a buffer solution, does the pH of the buffer go up or down? Use the Henderson - Hasselbalch equation to explain why this is so. Also use this equation to explain what happens when a strong base is added t o the buffer
1.3 What would you use to prepare a buffer system with a pH of around 4.2. What would you use to make a buffer with a pH of around 9.2? Describe the process you used to choose the correct buffer for each pH.
1.4 A buffer is made by mixing NH4Cl and NH3. Which is the acid component and which is the base component? What is the Ka and pKa for this buffer?
1.5 A buffer is made by mixing 0.30 moles of propanoic acid, C H 3 C H 2 COOH , and 0.20 moles of sodium propanoate, CH 3 CH 2 COO^- N a + . What will the pH of the solution be?
1.6 For the solution in question 5, show the reaction that takes place when a strong acid , HCl, is added to the solution. Show the reaction that takes place when a strong base, NaOH, is added to the solution.
1.7 When a strong acid is added to a buffer solution, does the pH of the buffer go up or down? Use the Henderson - Hasselbalch equation to explain why this is so. Also use this equation to explain what happens when a strong base is added t o the buffer
1.4 A buffer is made by mixing NH4Cl and NH3. Which is the acid component and which is the base component? What is the Ka and pKa for this buffer?
1.5 A buffer is made by mixing 0.30 moles of propanoic acid, C H 3 C H 2 COOH , and 0.20 moles of sodium propanoate, CH 3 CH 2 COO^- N a + . What will the pH of the solution be?
1.6 For the solution in question 5, show the reaction that takes place when a strong acid , HCl, is added to the solution. Show the reaction that takes place when a strong base, NaOH, is added to the solution.
1.7 When a strong acid is added to a buffer solution, does the pH of the buffer go up or down? Use the Henderson - Hasselbalch equation to explain why this is so. Also use this equation to explain what happens when a strong base is added t o the buffer
Explanation / Answer
1.3) pH = 4.2 is an Acidic Buffer which is made from weak acid and salt of the weak acid when reacted with strong base. Eg: CH3COOH + CH3COONa
pH = 9.2 is a Basic Buffer which is made from weak base and salt of the weak base when reacted with strong acid. Eg:CH3NH2 + CH3NHCl
pH = pKa + log([salt]/[acid])
POH = pKb + log([salt]/[base])
1.4) NH3 is the basic components
HCl is the acid component. NH4Cl is a salt of strong acid and weak base.
Kb value for NH3 is 1.8 * 10^-5
Ka = 5.55 * 10^-10
pKa = 9.255
1.5) Ka for etanoic acid = 1.8*10^-5
pH = pKa + log([salt]/[acid]) = 4.57
1.6) CH3CH2COO Na + HCl ---> CH3CH2COOH + Na+ + Cl-
CH3CH2COO Na + NaOH ----> CH3CH2COO - + 2Na+ + OH -
1.7) pH = pKa + log([salt]/[acid])
The buffer solution restricts pH change upto a certain extent. The acid undergoes very little
dissociation so the addition of acid or base adds to the salt component and therefore pH
does not change.