Saved Bookmarks
| 1. |
Calculate pH of 10^-7 M HCl |
|
Answer» Solution :If we do not consider `[H_3O^+]` from the ionisation of `H_2O`. Then `[H_3O^+]=[HCL]=10^-7M` i.e., pH=7, which is a pH of a neutral solution, We know that HCl solution is acidic whatever may be the CONCENTRATION of HCl i.e., the pH value should be less than 7, In this CASE the concentration of the acid is very LOW `(10^-7M)`. Hence, the `H_3O^+ (10^-7M)` formed due to the AUTO ionisation of water cannot be neglected. So, in the case we should consider `[H_3O^+]` from ionisation of `H_2O` `[H_3O^+]=10^-7` (from HCl) +`10^-7` (from water) `=10^-7 (1+1)` `=2 times 10^-7` `ph=-log_10[H_3O^+]` `=-log_10(2 times 10^-7)=-[log 2+log 10^-3]` `=-log 2-(-7),log_10 10` `=7-log 2` `=7-0.3010=6.6990` =`6.70` |
|