Question

What gas is produced when magnesium is made to react with hydrochloric acid?
A) Hydrogen
B) Oxygen
C) Carbon dioxide
D) No gas is produced

Answer 1

This is a very good example of a single replacement reaction. Here, magnesium is oxidized, giving up two electrons (an oxidation-reduction reaction). Also, the produced gas is flammable.

Complete step by step answer:

When magnesium reacts with dilute hydrochloric acid, an aqueous solution of magnesium chloride and hydrogen gas are produced. The chemical equation is given:
$Mg(s) + 2HCl(aq) \to MgC{l_2}(aq) + {H_2}(g)$
As magnesium is an active metal it reacts with hydrochloric acid. This is a very good example of a single replacement reaction. As magnesium is more reactive than hydrogen it displaces it in the chloride compound. Magnesium is oxidized, giving up two electrons (an oxidation-reduction reaction). When the electrons from magnesium are transferred to it hydrogen is reduced from $H +$ ion to ${H_2}$ gas.
Additional information: To start the reaction, first we need to take $50c{m^3}$ of 1 M hydrochloric acid with the help of a measuring cylinder and then pour the acid into a conical flask. Then we have to half fill the bowl. Then we have to Fill another measuring cylinder with water and lastly after adding a 3 cm strip of magnesium ribbon to the flask we have to close the mouth of the flask as soon as possible.

Note:
The flammability of hydrogen gas can be demonstrated by carefully holding a match or fireplace lighter up to the popping hydrogen bubbles. An audible crackling sound is heard as the hydrogen burns. This particular reaction is used widely to demonstrate the characteristic reaction of metals with acid, a single replacement reaction. Even in most of the cases, it is used to demonstrate the generation of hydrogen gas.