Question

A 1.00 liter solution contains 0.39 M ammonia and 0.30 M ammonium nitrate.

If 0.15 moles of nitric acid are added to this system,
indicate whether the following statements are TRUE (T) or FALSE (F).

(Assume that the volume does not change upon the addition of nitric acid.)

A. The number of moles of NH₃ will increase.

B. The number of moles of NH₄⁺ will remain the same.

C. The equilibrium concentration of H₃O⁺ will increase.

D. The pH will decrease.

E. The ratio of [NH₃] / [NH₄⁺] will remain the same.

Answer 1

Answer – We are given, 0.39 M ammonia and 0.30 M ammonium nitrate

When new added strong acid in the base and its conjugate acid, then there is moles of base decrease and moles of conjugate acid increase. When we added strong acid it is reacted with base and formed the conjugate base, so moles of base consumed and decreased where conjugate base formed and moles of conjugate gets increased. So using these criteria the following statements where the true or false as follow -

A) The number of moles of NH₃ will increase – False, since there is moles of base decrease.

B) The number of moles of NH₄⁺ will remain the same- False, since there is conjugate acid moles increase.

C) The equilibrium concentration of H₃O⁺ will Increase-True, since there is addition of strong acid and there is increase the moles of acid.

D) The pH will decrease – True, since there is addition of strong acid and there is increase the moles of acid and ratio of the acid by base gets increased and the pOh gets more and pH decreased.

E) The ratio of [NH₃] / [NH₄⁺] will remain the same – False, since there is change in the moles of conjugate base and base and due to that change in molarity and also change in ratio.