Question

(a)- What happens when an acid reacts with a metal? Give a chemical equation of the reaction involved.
(b)- Which gas is usually liberated when an acid reacts with a metal? How will you test for the presence of this gas?

Answer 1

Hint: In an acid, there are two parts: a positive part and a negative part. Metal is always a positive element so, when it is reacted with an acid, the negative part will attach with the metal. When the acid reacts with acid then there is a release of gas having atomic number 1.

Complete Solution :
(a)- When the metal is reacted with acid there is the formation of a salt and there is the liberation of hydrogen gas. In an acid, there are two parts: a positive part and a negative part. Metal is always a positive element so, when it is reacted with an acid, the negative part will attach with the metal. Let us take metal, sodium ($Na$), and an acid hydrochloric acid ($HCl$), so the reaction will be:
$2Na+2HCl\to 2NaCl+{{H}_{2}}$
Therefore, in this equation, $NaCl$ is salt.
(b)- As discussed above when an acid and a metal react with each other, then there is the formation of a salt and there is the liberation of hydrogen gas. We can test this gas, when the reaction occurs there is the formation of bubbles, these bubbles are passed through the soap solution, gas-filled soap bubbles will rise. Now a burning candle is brought near these bubbles, the bubbles burst with a ‘pop’ sound. This is due to the presence of hydrogen gas.

Note: When an acid and a metal react a salt is formed because all the metals are basic in nature. The making of the 'pop' sound is the property only of the hydrogen gas.