Part A For 500.0 mL of pure water, calc ulate the initial pH and the final pH af
ID: 965145 • Letter: P
Question
Part A
For 500.0 mL of pure water, calculate the initial pH and the final pH after adding 0.010 mol of HCl.
Express your answers using two decimal places separated by a comma.
pH initial, pH final =
Part B
For 500.0 mL of a buffer solution that is 0.155 M in HC2H3O2 and 0.135 M in NaC2H3O2, calculate the initial pH and the final pH after adding 0.010 mol of HCl.
Express your answers using two decimal places separated by a comma.
pH initial, pH final=
Part C
For 500.0 mL of a buffer solution that is 0.180 M in CH3CH2NH2 and 0.165 M in CH3CH2NH3Cl, calculate the initial pH and the final pH after adding 0.010 mol ofHCl.
Express your answers using two decimal places separated by a comma.
pH initial, pH final=
Explanation / Answer
part A :
for pure water pH = 7
initial pH = 7
molarity of HCl = 0.01 / 0.5 = 0.02 M
pH = -log [H+] = -log 0.02 = 1.7
pH final = 1.7
pH initial, pH final = 7.00 , 1.70
b)
pH = pKa + log [salt / acid]
= 4.74 + log [0.135 / 0.155]
= 4.68
pH = pKa + log [salt - C / acid+C]
= 4.74 + log [0.135 - 0.02 / 0.155 + 0.02]
= 4.56
pH initial, pH final= 4.68 , 4.56
c)
pOH = pKb + log [salt / base]
= 3.2 + log [0.165 / 0.180]
= 3.16
pH = 10.84
pOH = pKb + log [salt + C/ base - C]
= 3.2 + log [0.165 + 0.02 / 0.180 - 0.02]
= 3.26
pH = 10.74
pH initial, pH final= 10.84 , 10.74