Question

What type of oxides is formed by metals?

(a) Oxides with pH = 7

(b) Oxides with pH > -log10[1 x 10^-7]

(c) Oxides with pH <= -log10[1 x 10^-7]

(d) Amphoteric oxides

The question was posed to me during an interview.

Question is from P-Block Elements topic in chapter P-Block Elements of Chemistry – Class 12

Answer 1

Correct option is (b) Oxides with pH > -log10[1 x 10^-7]

For explanation I would say: Metals usually form basic oxides. E.g. sodium, potassium,  calcium. Meaning, the pH of the salts is greater than 7 on the pH scale. pH is calculated as the negative logarithm of concentration of hydronium ions. Metals form oxides because upon dissolution, they release oxide ions which in turn give hydroxide (basic) ions. However, a few metals form oxides which are both acidic and basic, called amphoteric oxides. E.g.  zinc, lead.