Calculate and compare the masses of 0.5 mole of $\mathrm{CO}$ and 0.5 mole of ${\mathrm{N}}_2$.

Write the molecular formula of zinc phosphate ${\mathrm{Zn}}_{\mathrm{x}}{\left({\mathrm{PO}}_{\mathrm{y}}\right)}_{\mathrm{z}}$

The value of x, y and z in the formula can be-

A. x = 4, y = 2, z = 3

B. x = 2, y = 3, z = 4

C. x = 3, y = 4, z = 2

"Enter your correct answer as A, B or C."

The molecular formula of the following is:
Aluminium oxide (the valency of aluminium = $3$ and the valency of oxygen = $2$)

A: ${\mathrm{Al}}_2{\mathrm{O}}_3$

B: $\mathrm{AlO}$

C: ${\mathrm{Al}}_3{\mathrm{O}}_3$ 

Enter the correct answer as " A, B or C " in the given blank.

The molecular formula of the sodium sulphate (the valency of sodium is 1 and the valency of sulphate = 2)

A: ${\mathrm{NaSO}}_4$

B: ${\mathrm{Na}}_2{\mathrm{SO}}_4$

C: $\mathrm{NaO}$

Enter the answer as A, B or C.

Select the formulae of elements and compounds from the following list:

$\mathrm{NO}, {\mathrm{N}}_2, {\mathrm{CO}}_2, \mathrm{HCl}, {\mathrm{Cl}}_2, \mathrm{CO}, \mathrm{Hg}, \mathrm{Unh}$

Calculate the mass of the following,

$0.3$mole of ammonia.

Calculate the mass of the following,

$0.1$ mole of carbon dioxide.

Calculate the mass of the following,

$6.022 \times {10}^{23} \mathrm{molecules} \mathrm{of} {\mathrm{H}}_2\mathrm{O}$.