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How many molecules are there in 14g of nitrogen gas at s....

How many molecules are there in 14g of nitrogen gas at s.t.p? (n = 14, Avogadro Number = 6. 0 x 1023mol-1)

A.

1.2 x 10 23

B.

3.0 x 1023

C.

6.0 x1023

D.

1.2 x 1024

E.

30 x1023

Correct answer is B

mass of nitrogen gas = 14g, molar mass of nitrogen gas = 28gmol-1

mole = massmolarmass=noofparticlesavogadrosno

moles =  1428=noofparticles6.0×1023

no of molecules = 0.5 x 6.0 x 1023

=  3.0 x 1023molecules.