Explanation:
The formula of nitrogen gas is given as;
N₂
Given volume of the gas = 120cm³
Now,
We need to find the number of molecules and the mass of this compound
Solution:
At STP;
1 mole of gas occupies a volume of 1dm³ ;
1000cm³ = 1dm³
120cm³ gives 0.12dm³;
Now;
1dm ³ of gas contains 1 mole of substance at STP
0.12dm³ will contain 0.12mole of nitrogen gas at STP
Mass of N₂ gas = number of moles x molar mass of N₂
Molar mass of N₂ = 2(14) = 28g/mol
Mass of N₂ = 0.12 x 28 = 3.36g
1 mole of a substance contains 6.02 x 10²³ molecules
0.12 mole of N₂ will contain 0.12 x 6.02 x 10²³ = 7.22 x 10²²molecules
