Question

When an acid reacts with a metal, which gas is evolved, and what is the other corresponding product?
A. Hydrogen, Salt
B. Hydrogen, Hydroxide
C. Hydroxide, Salt
D. None of these

Answer 1

Hint: Metals that are more reactive than acids undergo a single displacement reaction with acid and form hydrogen gas and corresponding salt. A single displacement is defined as that reaction that involves the replacement of the least reactive element by a more reactive element in a compound.

Complete step by step solution:
When an acid reacts with metal, hydrogen gas is evolved and the corresponding product formed is salt. The general chemical reaction of an acid with metal is written as:
Metal + Acid → salt + hydrogen
For example, if zinc reacts with the sulphuric acid then there is the formation of the zinc sulphate salt and hydrogen gas, which is shown below:
$Zn + {H_2}S{O_4} \to ZnS{O_4} + {H_2} \uparrow $

The hydrogen gas formed during the reaction of metal with acid can be identified by the following experiment:
When acid and metals react together there are observed gas bubbles, and when these gas bubbles pass through the soap solution then gas filled soap bubbles rise into the air and when a burning candle is brought near these gas-filled soap bubbles then the gas present in soap bubbles burns with a ‘pop’ sound. This shows that the gas evolved is hydrogen gas. Hydrogen gas produced a ‘pop’ sound because the energy released during the burning of hydrogen gas has kinetic energy that expands

So, the correct answer is Option A.

Note: t may be noted that the metal that is above hydrogen in the activity series will replace the hydrogen from acid in a single replacement reaction. The activity series is defined as the arrangement of the metal in decreasing order of reactivity.