WAEC - Chemistry (1990 - No. 11)
How many molecules are there in 14g of nitrogen gas at s.t.p? (n = 14, Avogadro Number = 6. 0 x \(10^{23 }\)mol-1)
1.2 x 10 23
3.0 x 1023
6.0 x1023
1.2 x 1024
30 x1023
Explanation
mass of nitrogen gas = 14g, molar mass of nitrogen gas = 28gmol-1
mole = \(\frac{mass}{molar mass} = \frac{ no of particles }{ avogadro's no }\)
moles = \(\frac{14}{28} = \frac{ no of particles }{ 6.0 \times 10^{23}}\)
no of molecules = 0.5 x 6.0 x \(10^{23}\)
= 3.0 x \(10^{23}\)molecules.
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