The dissociation of weak electrolyte (a weak base or weak acid) is expressed in terms of Ostwald's dilution law. An acid is substance which furnishes a proton or accepts an electron pair, where a base is proton acceptor or electron pair donor. Stronger is acid, weaker is its conjugate base. The dissociation constants of an acid `(K_(a))` and its conjugate base `(K_(b))` are related by `K_(w)=K_(a)xxK_(b)`, where `K_(w)` is ionic product of water equal to `10^(-14) at 25^(@)C`. The numerical value of `K_(w)` however increase with temperature. In a solution of an acid or base `[H^(+)][OH^(-)]=10^(-14)`. Thus the `[H^(+)]` in a solution is expressed as: `[H^(+)]=10^(-pH)` and `pH+pOH=14`. Buffer solution are the solutions which do not show appreciable change in the pH on addition of small amount of acid or base.
`0.16g of N_(2)H_(4)(K_(b)=4xx10^(-6))` are dissolved in water and the total volume of solution is made upto 500 mL. The percentage of `N_(2)H_(4)` that reacts with water is:

Options

A. `2%`
B. `3%`
C. `1%`
D. `4%`

Answer

A

Explanation

`{:(N_(2)H_(4)+H_(2)OhArr,N_(2)H_(5)^(+)+,OH^(-)),(1,0,0),(1-alpha,alpha,alpha):}`
`K_(b) = Calpha^(2)`
`:. alpha= sqrt((K_(b))/(C ))= sqrt((4xx10^(-6))/((0.16)/(32)xx(1000)/(500)))=0.02 or 2%`