JEE Main levelSingle correct optionDifficulty 2 of 3ia098
100mL of 0.10MNaX2COX3 is mixed with 60mL of 0.10MHCl. For HCOX3X−, pKa2=10.33. With log2=0.301 and log3=0.477, the pH of the resulting solution is
A9.93
B10.33
C10.15
D10.51
Answer: C
COX3X2−+HX+→HCOX3X−: 10mmol carbonate and 6mmol acid give 6mmolHCOX3X− and 4mmolCOX3X2− left. pH=10.33+log(4/6)=10.33+0.301−0.477=10.15.