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A buffer solution of `pH` value `4` is to be prepared, using `CH_(3)COOH` and `CH_(3)COONa`.How much amount of sodium acetate is to be added to `1.0L` of `M//10` acetic acid? `(K_(a) = 2.0 xx 10^(-5))` |
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Answer» For an acidic buffer containing aceetic acid, `CH_(3)COOH`, and sodium acetate, `CH_(3)COONa`, we have `[H^(o+)] = (K_(a) ["acid"])/[("salt")]` (Use this formula, rather than) `pH = pK_(a) + "log" (["salt"])/(["acid"])` `[CH_(3)COOH] = 0.1M,` `[H^(o+)] = 10^(-4)` and let `[CH_(3)COONa] = xM` `rArr [H^(o+)] = 10^(-4) = (2xx10^(-5)xx0.1)/(x)` `rArr x = 0.02` mol, i.e. `0.02` mol of `CH_(3)COONa` is required. |
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