Question

What's the pH of a solution composed of 0.2 moles of NH3 and 0.15 moles of nh4cl​

Answer 1

`pH=4.63`

Step-by-step explanation:

Hello!

In this case, since the ionization of ammonia, which is a weak base, is written as:

`NH_3+H_2O\rightleftharpoons NH_4^++OH^-`

We can see that the ammonium ion is the conjugate acid whereas the hydroxide ions the conjugate base; that is why we use the Henderson-Hasselbach equation to compute the pH, given the pKb of ammonia 4.75:

`pH=pKb+log(([conj\ acid])/([base]) )`

In such a way, for the given moles of ammonia, base, and those of ammonium chloride, conjugate acid form, we obtain:

`pH=4.75+log((0.15)/(0.2) )\\\\pH=4.63`

Best regards!