Question

The elements whose oxides can turn litmus solution red are ______.

Options

• lithium and sodium

• copper and potassium

• carbon and hydrogen

• phosphorus and sulphur

Answer 1

The elements whose oxides can turn litmus solution red are phosphorus and sulphur.

Explanation:

Litmus solution turns red in the presence of an acid. Phosphorus and sulphur are non-metals that form non-metallic oxides (P₄O₁₀ and SO₂), which dissolve in water to produce strong acidic solutions (phosphoric and sulphurous acids). Conversely, metals such as lithium, sodium, copper, and potassium form basic oxides, whereas hydrogen forms water (H₂O), which is neutral.