Question

200 grams of marble chips are dropped into 100g of hydrochloric acid. How much chips will remain undissolved? What weight of anhydrous calcium chloride and what weight of $C{O_2}$ gas could be obtained from it?
$CaC{O_3} \to CaO + C{O_2}$

Answer 1

We need to find out the number of moles. By balancing the stoichiometric coefficients of the reaction, we get the number of moles from the mass. Concept of limiting agents shall also be used.

Formula used: $n = \dfrac{{{\text{weight of substance}}}}{{{\text{molar mass of substance}}}}$
Here, $n$ is the number of moles.

Complete step by step solution:
We already know the molar masses of calcium carbonate and Hydrochloric acid.
We will first find out the number of moles,
${\text{Moles of CaC}}{{\text{O}}_{\text{3}}}{\text{ = }}\dfrac{{{\text{200}}}}{{{\text{100}}}}{\text{ = 2moles}}$
Similarly, we find moles of HCl:
${\text{n}}\left( {{\text{HCl}}} \right){\text{ = }}\dfrac{{{\text{100}}}}{{{\text{36}}{\text{.5}}}}{\text{ = 2}}{\text{.74 moles}}$
On balancing the equation and mentioning the bi- products we get,
$CaC{O_3} + 2HCl \to CaC{l_2} + C{O_2} + {H_2}O$
${\text{0}}{\text{.63 1}}{\text{.37 1}}{\text{.37 1}}{\text{.37}}$
So, here HCl is limiting reagent.
And $0.63$ moles of $CaC{O_3}$ which is equal to 63 gm remains undissolved.
Also, $1.37$ moles of $CaC{l_2}$ ​ are formed which has a mass equal to $111 \times 1.37 = 152.67{\text{gm}}$
Finally, $1.37$ moles of $C{O_2}$ ​ are formed and its mass = $44 \times 1.37 = 60.28{\text{gm}}$
Hence, mass of carbon dioxide formed is $60.28{\text{gm}}{\text{.}}$

Note:
This type of question requires a lot of calculation which should be done very carefully especially when taking the no of moles.
Some facts about calcium carbonate are: It is a chemical compound with the chemical formula $CaC{O_3}$ . It is a white insoluble powder-like substance which occurs naturally in minerals, chalk, marble, limestone, calcite, shells, pearl, etc. Medicinally, it is used as an antacid or as a calcium supplement.
Also, here the concept of limiting agent comes. It is the reactant in a chemical reaction that limits the amount of product that can be formed. The reaction will stop when all of the limiting reactant is consumed whereas excess reactant is the reactant in a chemical reaction that remains when a reaction stops when the limiting reactant is completely consumed.