Question:
Fill in the blanks
(a) In a chemical reaction, the sum of the masses of the reactants and products remains unchanged. This is called ………….. .
(b) A group of atoms carrying a fixed charge on them is called ………….. .
(c) The formula unit mass of Ca3(PO4)2 is ………….. .
(d) Formula of sodium carbonate is ………… and that of ammonium sulphate is …………… .
Solution:
(a) Law of conservation of mass
(b) Polyatomic ions
(c) $3 \times$ Atomic mass of $\mathrm{Ca}+2 \times$ Atomic mass of $\mathrm{P}+8 \times$ Atomic mass of $\mathrm{O}$. $3 \times 40+2 \times 31+8 \times 16=120+62+128=310 u$
(d) $\mathrm{Na}_{2} \mathrm{CO}_{3},\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}$.