Dalton used the symbol _____ for oxygen and _____ for hydrogen.

Write the valency of fluorine in ${\mathrm{CaF}}_2$.

Calculate the molecular mass of the following:

${\mathrm{Na}}_2{\mathrm{SO}}_4.10{\mathrm{H}}_2\mathrm{O}$

(Atomic masses of $\mathrm{Na}, \mathrm{S}, \mathrm{O}$ and $\mathrm{H}$ are $23 \mathrm{amu}, 32 \mathrm{amu}, 16 \mathrm{amu}$ and $1 \mathrm{amu}$ respectively)

Correct the following statement:

Formula of iron $\left(\mathrm{III}\right)$ oxide is $\mathrm{FeO}$.

Calculate the relative molecular mass of ${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}$.

Atomic masses: $\mathrm{Cu}= 63 \mathrm{amu}, \mathrm{S}= 32 \mathrm{amu}, \mathrm{O}= 16 \mathrm{amu}, \mathrm{H}= 1 \mathrm{amu}$