Question

$2.24c{m}^3$ of dry ammonia gas contain $6\times {10}^{22}$ molecules at S.T.P. Calculate the number of molecules in $56c{m}^3$ of dry nitrogen at S.T.P.

Answer 1

At STP, $1mole$ gas occupies $22.4litre$ volume.

So, $56c{m}^3$ gas have $\frac{56}{22.4\times 1000}moles$

Number of moles of dry Nitrogen at STP $=2.5milimoles$

Number of molecules of dry Nitrogen $=2.5\times {10}^{-3}\times N_A$

$N_A=$ Avogardo Number $=6\times {10}^{23}$

So, Nitrogen have $15\times {10}^{20}molecules$ or $1.5\times {10}^{21}molecules$