Answer:
1) pH = 5.05
2) pH = 5.13
3) pH = 4.97
Explanation:
Step 1: Data given
Number of moles of propionic acid = 0.18 moles
Number of moles sodium propionate = 0.26 moles
Volume = 1.20 L
Ka = 1.3 * 10^-5 → pKa = 4.989
Step 2: Calculate concentrations
Concentration = moles / volume
[acid]= 0.18/ 1.2 =0.150 M
[salt]= 0.26/ 1.3 = 0.217 M
pH = 4.89 + log(0.217/0.150)=<u>5.05</u>
<u />
<u />
<u />
What is the pH of the buffer after the addition of 0.02 mol of NaOH?
moles acid = 0.18 - 0.02 = 0.16
[acid]= 0.16/ 1.2=0.133 M
moles salt = 0.26 + 0.02 = 0.28
[salt]= 0.28/ 12=0.233
pH = 4.89 + log 0.233/ 0.133 = 5.13
What is the pH of the buffer after the addition of 0.02 mol of HI?
moles acid = 0.18+ 0.02 = 0.20 moles
[acid]= 0.20/ 1.2 = 0.167 M
[salt]= 0.26 - 0.02= 0.24 moles
[salt]= 0.24/ 1.2 = 0.20 M
pH = 4.89 + log 0.20/ 0.167= 4.97
