How many molecules of ammonia gas are present in $67.2 \ dm^3$,measured at $S.T.P.$?

How many moles of nitrogen atoms are present in $8 \ g$ of ammonium nitrate (in $mol$)?

How many moles of oxygen gas at $STP$ are equivalent to $5.6 \ L$?

How many moles of $Al_2(SO_4)_3$ are present in $50 \ g$ of the substance?

$A$ thin layer of cobalt is deposited on a plate with a total area of $0.5 \ m^2$ and a thickness of $0.005 \ cm$. How many cobalt atoms are deposited on the plate? (Density of cobalt $= 8.9 \ g \ cm^{-3}$,Atomic mass of $Co = 59 \ g \ mol^{-1}$)

The number of electrons in a mole of hydrogen molecule is