Question

Be sure to answer all parts. a buffer is prepared by mixing 50.0 ml of 0.050 m sodium bicarbonate, nahco3, and 10.7 ml of 0.10 m naoh. (ka = 4.7 × 10−11) what is the ph?

Answer 1

Moles HCO3- = 0.0500L×0.050M =0.0025
Moles OH - added =0.0107L×0.10M =0.00107
Moles CO32 - forms= 0.00107
Moles HCO3 - in excess =0.0025-0.00107=0.00143
Total volume = 10.7 +50.0 =60.7mL = 0.0607L
[HCO3-]= 0.00143/ 0.607 =0.0236M
[CO32-]= 0.00107/0.0607 = 0.0176M
pKa = 10.3
PH = 10.3 + log 0.0176/0.0236 =10.2.