1.

In what volume ratio should you mix 1.00 M solution NH_(4)Cl and 1.00 M NH_(3) to produce a buffersolution of pH 9.80 ? [pK_(b)(NH_(3))=4.74]

Answer»

`1:1.35`
`3.5 :1`
`2:1`
`1:2`

Solution :`[NH_(4)Cl]=V_(1)mL =V_(1)` millimol
`[NH_(3)]=V_(2)mL =V_(2)` millimol
`=pH =9.80 , POH =4.2`
`pOH =pK_(a)+LOG.(V_(1))/(V_(2))`
`4.2 =4.74 +log. (V_(1))/(V_(2))`
`-0.54=log. (V_(1))/(V_(2))`
or `log.(V_(2))/(V_(1))=0.54`
`(V_(2))/(V_(1))=` antilog `0.54=3.5`
Thusl, `(V_(2))/(V_(1))=(3.5 )/(1)`


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