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Calculate the pH of a buffermixture which contains 7.5gms if acetic acid and 10.25 gms of sodium acetate in 1 litre of the solution. K_a for acetic acid is 1.8xx10^(-5). |
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Answer» Solution :`pH=pK_a+log.(["salt"])/(["acid"])` The CONCENTRATION of the salt and the acid should be in MOLES/lit. Number of moles of acetic acid `("weight of acetic acid")/("molecular weight of acetic acid")=(7.5)/(60)` Number of moles of sodium acetate `=("weight of sodium acetate")/("molecular weight of sodium acetate")=(10.25)/(82)` `pK_a=-log K_a` `=-log 1.8xx10^(-5)` `=log .(1)/(1.8xx10^(-5))` `=log 1-log 1.8-log 10^(-5)` `=5-0.2553=4.7447` `therefore pH=4.7447+log.(0.125)/(0.125)` `pH=4.7447.` |
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