Question

One of the forms of a naturally occurring solid compound P is usually used for making the floors of houses. On adding a few drops of dilute hydrochloric acid to P, brisk effervescence are produced. When 50 g of reactant P was heated strongly, than 22 g of a gas Q and 28 g of a solid R were produced as products. Gas Q is the same which produced brisk effervescence on adding dilute HCl to P. Gas Q is said to cause global warming whereas solid R is used for white-washing.

1. What is (i) solid P (ii) gas Q, and (iii) solid R.
2. What is the total mass of Q and R obtained from 50 g of P ?
3. How does the total mass of Q and R formed compare with the mass of P taken ?
4. What conclusion do you get from the comparison of masses of products and reactant ?
5. Which law of chemical combination is illustrated by the example given in this problem ?

Answer 1

1. (i) Solid P is calcium carbonate (CaCO₃).
       (ii) Gas Q is carbon dioxide (CO₂).
       (iii) Solid R is calcium oxide (CaO).
2. When 50g of reactant P is heated, Q and R are produced. According to the law of conservation of mass, same amount of Q and R will be produced. Therefore, 50g of Q and R will be produced on heating 50g of P.
3. According to the law of conservation of mass, same amount of Q and R will be produced depending upon  the amount of P by mass.
4. When we compare the mass of reactants to that of their product, it will be seen that the total mass of the reactants is equal to the total mass of their product.
5. In the example, the law of conservation of mass proposed by Antoine Lavoisier is illustrated.