Calculate the number of moles and molecules of ammonia `(NH_3)` gas in a volume 67.2 dm3 of it measured at STP.

Explanation

Volume of `NH_3` at STP = 67.2` dm^3`
molar volume of a gas = 22.4 `dm^3 "mol"^(-1)`
Number of moles (n) `= ("Volume of the gas at STP ")/("Molar volume of gas ")`
Number of moles of `NH_3 = (67.2 dm^3)/(22.4 dm^3 "mol"^(-1))` = 3.0 mol
Number of molecules = Number of moles `xx 6.022 x× 10^23` molecules `"mol"^(-1)`
Number of molecules of `NH_3` = 3.0 mol `xx 6.022 x 10^23 `molecules `"mol"^(-1)`
` = 18.066 x× 10^23` molecules