Question

Dilute hydrochloric acid reacts with magnesium ribbon:
The reaction is:
A. $Mg+2HCl⟶{MgCl}_2+H_2$
B. $Mg+2HCl\to {MgH}_2+{Cl}_2$
C. $Mg+2HCl\to Noreaction$
D. None of these

Answer 1

Hint: The reaction between magnesium ribbon and dilute hydrochloric acid is a redox reaction. Here, both reduction and oxidation will take place.

Complete step-by-step answer:
The following chemical reaction will takes place;
$Mg+2HCl⟶{MgCl}_2+H_2$

Here,as the oxidation state changes from 0 to +2, magnesium metal is getting oxidized to
magnesium cation, ${Mg}^{2+}$ whereas the oxidation state of hydrogen is changed from +1 to 0, it means it is getting reduced.
So, we can say that magnesium is acting as a reducing agent and hydrogen is acting as an oxidizing agent in this reaction.
When magnesium ribbon reacts with hydrochloric acid, magnesium chloride will be formed and hydrogen gas is liberated.
There will be a change in temperature of the test tube, slight fizzing of gas bubbles,then the magnesium ribbon will dissolve into water, leaving in blue.
Hence, the correct option is (a).

Additional Information:
The rate of reaction remains constant with the change in time. This is because magnesium is solid and its concentration is assumed as unity. So, there will be no change in the concentration of magnesium with time.

Note: It is a single displacement reaction. The possibility for the mistake is that you can choose the option (b) as you might get confused that magnesium cannot displace hydrogen but magnesium is above hydrogen in electrochemical series, so it displaces hydrogen and hydrogen gas is produced.