Question

(a) What happens when an acid reacts with a metal? Give 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

Answer:

[a] When acids react with metals, they produce a salt and hydrogen gas. ... The general equation that describes the chemical reaction between an acid and metal is metal + acid = salt + hydrogen gas.

2HCL +Mg--->MgCl2+H2

[b] when an acid reacts with an active metal HYDROGEN gas is liberated.

EXCEPTION - acids does not react with element bellow hydrogen in activity series of metals to give hydrogen because such metals cannot displace hydrogen from the acid

EXAMPLE -

Zn + H2SO4 ------> ZnSO4 + H2

TEST -

1)Burning wooden splinter is extinguished in hydrogen

2)hydrogen burns with a pale blue flame producing pop sound.

Answer 2

Explanation:

(a) Metal chemical reaction:

• When acid reacts with metal, to form the salt and hydrogen gas is produced as products. The salt produced is the mixture of metal and acid. The general reaction is given below:
• $\text {Metal}+\text {Acid} \rightarrow \text {Salt}+\text {Hydrogen gas}$
• When magnesium reacts with hydrochloric acid to form magnesium chloride and hydrogen gas.

       $M g+2 H C l \rightarrow M g C l_{2}+H_{2}$

(b) Testing of gas:

The gas produced when reaction between metal and acid is hydrogen gas.  

We can test the gas by the following steps:

• Step 1: Place the acid and metal in the test tube.
• Step 2: Close the test tube with a cork and fix a glass tube to the cork.
• Note: The gas produced due to reaction will pass through the tube.  
• Step 3: Place a candle at the end of the glass tube.
• Result: The light of the candle blows out with a pop sound.

From this, we can understand, the gas produced and the flame does not react with each other. The reaction produces water with reddish flame. So, flame blows out with a pop sound.