Question

If 6.3 g of \[NaHC{O_3}\] are added to 10 gm of \[HCl\] solution, the residue is found to weigh 12 gm. What is the mass of \[C{O_2}\] released in this reaction?
A.43 gm
B.21.5 gm
C.50 gm
D.4.3 gm

Answer 1

Hint: Law of conservation of mass can be used in this question to get the answer directly. In this law the mass can neither be created nor be destroyed but can be converted from one form to another. So by putting weights of reactants and product equal, answers could be obtained.

Complete Step by step answer:
In the given question, two reactants are reacted to form products and mass of product is being asked in the question. Now this becomes a case of Law of conservation of mass in a chemical reaction which could be used to get the answer.
Law of conservation of mass states that mass can neither be created nor be destroyed but can be only transformed into one form to another.
And in chemical reactions, the total mass of reactants will be equal to the total mass or products, and the atom cannot be created itself and therefore mass as well.
So, by following this definition, we will see the reaction that is occurring and represented as follows: -
\[NaHC{O_3}\left( s \right){\text{ }} + {\text{ }}HCl{\text{ }} \to {\text{ }}NaCl(s){\text{ }} + {\text{ }}{H_2}O{\text{ }} + {\text{ }}C{O_2}(g)\]
So according to the question, 6.3 gm of \[NaHC{O_3}\] and 10 gm of \[HCl\] are used which is the reactants
Mass of reactants = 6.3 + 10 = 16.3 gm
Given that mass of residue which means mass of \[NaCl{\text{ }}and{\text{ }}{H_2}O\] = 12 gm
Let us assume \[C{O_2}\] released = x gm
So, according to law of conservation of mass
16.3 = 12 + x
From this we can calculate x i.e. x = 16.3-12 = 4.3 gm
Therefore, weight of \[C{O_2}\]released = 4.3 gm

So, the correct option is D i.e. 4.3 gm

Note: This reaction in the question was simple acid base reaction (acid and base react to give salt and water). These are the basic laws which are followed in the whole universe and in every reaction, and also there are other laws like laws of constant proportions etc. So, all these are important and should be known to answer similar types of questions very easily.