To a 50 ml of 0.05m formic acid how much volume of 0.1m sodium formate must be added to get a buffer of ph 4
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Let x ml of 0.10M sodium formate is added,
No. of moles in xml of 0.10M sodium formate is = 1.1*x/1000
No. of moles in 50ml xml of 0.05M formic acid is = 0.05*50/1000
Therefore, [sodium formate] / [formic acid] = (0.01*x/1000)/(0.05*50/1000)
= 0.04x
From Henderson's equation:
pH = pKa + log[salt]/[acid]
=>4 = 3.8 + log 0.04x
=> log 0.04x = 0.2
=> x = 39.6 ml
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