Question

Which of the following reactions will result in the formation dihydrogen gas?

• A. A reaction of potassium with cold water.
• B. A reaction of sodium with cold water.
• C. A reaction of sodium with oxygen.
• D. A reaction of potassium with oxygen.

Answer 1

Answer: (A), (B)

The correct options are
A A reaction of potassium with cold water.
B A reaction of sodium with cold water.

Highly reactive metals like potassium, sodium, and calcium, when exposed to cold water, liberate dihydrogen gas along with energy.
Eg:
$2K+H_{2}O\to 2KOH+H_2$