What will be the mass of hydrogen atom in amu?

The formula of washing soda is _____.

(A) ${\mathrm{Na}}_2{\mathrm{CO}}_3.10{\mathrm{H}}_2\mathrm{O}$              (B) ${\mathrm{Na}}_2{\mathrm{CO}}_3$                (C) ${\mathrm{Na}}_2{\mathrm{CO}}_3.2{\mathrm{H}}_2\mathrm{O}$

Enter your correct answer as A, B or C.

Limestone is _____.

(A) ${\mathrm{CaCO}}_3$                  (B) $\mathrm{CaO}$                   (C) $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$

Enter your correct answer as A, B or C.

Formula of iron (III) carbonate is _____.

(A) ${\mathrm{Fe}}_2({\mathrm{CO}}_3{)}_3$                       (B) ${\mathrm{FeCO}}_3$                    (C) ${\mathrm{Fe}}_3({\mathrm{CO}}_3{)}_2$

Enter your correct answer as A, B or C.