Question

A gas is formed by the reaction between marble pieces and dilute HCl.
(A) Which gas is formed as the result of this equation?
(B) Write the balanced chemical equation for this reaction.
(C) Suggest two ways of increasing the speed of the chemical reaction.

Answer 1

Hint: All mineral acids react with Marble forming salts with the liberation of $C{O_2}$ gas. Marble is chemically calcium carbonate i.e. $CaC{O_3}$ . When dilute HCl is added to calcium carbonate, it forms calcium chloride, water and carbon dioxide. This information alone suffices the purpose of the approach used.

Complete step-by-step answer:

(A) The gas formed as the result of this chemical reaction is – Carbon Dioxide i.e. $CO_2$.
(B) The balanced chemical equation for this reaction is –
Chemically marble is calcium carbonate that is $CaC{O_3}$. When dilute hydrochloric acid is added to marble pieces that are calcium carbonate, it forms calcium chloride, water and carbon dioxide gas.
The balanced chemical equation for the reaction is as follows –
$CaC{O_3} + 2HCl\xrightarrow{{}}CaC{l_2} + {H_2}O + C{O_2}..............(i)$
The calcium carbonate present in the marble is basic in nature and hence in the above reaction it neutralizes the hydrochloric acid and as a base is defined as “a compound that reacts with an aqueous solution of an acid to produce a water and salt solution in which the salt gets separated into its component ions.” Whenever the aqueous solution gets saturated by a given salt solute, any such extra salt gets precipitated out of the solution.

(C) The two ways of increasing the speed of the chemical reaction are –
(a) We can increase the temperature of the reaction mixture and hence thereby increasing the speed of the reaction. (Marble pieces + Dilute HCL)
(b) Or we can crush the marble pieces into small grains or turn it into the fine powdered form and then add dilute HCL into it followed by frequent stirring.

Note – All mineral acids decompose the marble that is calcium carbonate into soluble salts and carbon dioxide gas. When the carbon dioxide gas escapes, the mass of the reaction mixture decreases continuously.