1.

A buffer solution with pH 9 is to be prepared by mixing `NH_(4)Cl` and `NH_(4)OH`. Calculate the number of moles of `NH_(4)Cl` that should be added to one litre of `1.0 M NH_(4)OH`. `[ K_(b) = 1.8 xx 10^(-5)]`A. 3.4B. 2.6C. 1.5D. 1.8

Answer» Correct Answer - D
`pH = -log K_(b) + log. (["Salt"])/(["Acid"])`
`pH = -log[1.8 xx 10^(-5)] + log.(["Salt"])/(1.0)`
`9 = 4.7 + log.(["Salt"])/(1.0)`
`log.(["Salt"])/(1.0) = 9 - 4.7 = 4.3`
`(["Salt"])/(1.0) = "Antilog" (1)/(4.3), ["Salt"] = 1.8`.


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