Question

The addition of NaOH to water would result in which of the following?

A) A decrease in [H3O+] and an increase in pH
B) A decrease in [H3O+] and a decrease in pH
C) An increase in [H3O+] and an increase in pH
D) No change in [H3O+] and an increase in pH
E) No change in [H3O+] and no change in pH

Answer 1

A decrease in [H3O+] and an increase in pH (option a)

Step-by-step explanation:

Equilibrium of water is shown in this equation

2H₂O ⇄ H₃O⁺ + OH⁻

When you add NaOH, you are modifying [OH⁻]

NaOH → Na⁺ + OH⁻

In equilibrium of water, the [OH⁻] increases

2H₂O ⇄ ↓ H₃O⁺ + OH⁻ ↑

As the [OH⁻] increases, by Le Chatellier, the equilibrium tends to decrease [H₃O⁺].

If the [OH⁻] is higher, pH is also high so the solution of water and sodium hydroxide would be totally basic.