Exercise 9.11
5. g of sodium carbonate and g of acetic acid react to produce g of carbon dioxide, g of water, and g of sodium acetate. Verify whether the law of conservation of mass is valid.
Not cross-checked
NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.
The Law of Conservation of Mass is valid — the total mass is $\displaystyle 11.3$ g both before and after.
Total mass of reactants \(\displaystyle = 5.3 + 6.0 = 11.3\) g.
Total mass of products \(\displaystyle = 2.2 + 0.9 + 8.2 = 11.3\) g.
Mass of reactants = mass of products, so no matter was created or destroyed — the atoms have only rearranged.
Note that carbon dioxide gas is released here, so the reaction must be carried out in a closed container; in an open one the escaping gas would make the final reading $\displaystyle 2.2$ g short, exactly as in Activity $\displaystyle 9.2$, set-up 1.