Question

Calculate the number of moles for the following:
a) 4.6g Sodium
b) 120g Carbon
c) 12.044x1023 molecules of Chlorine

Answer 1

a) 4.6g Na

1 mole Na contains 23 g Na

23 g Na =1 mole of Na

1 g Na= 1/23 moles of Na

4.6 g Na= 1/23×4.6= 4.6/23=0.2 moles

Therefore 0.2 moles are present in 4.6 g of Na

b) 120g

No. of g-atoms of Carbon = $\sf \frac{at.\ mass\ of\ carbon}{mass\ of\ carbon} = \frac{120}{12} = 10$

∵ 1 g-atom of carbon has no. of atoms =6.023 × 10²³

∴ 10 g-atoms of carbon has no. of atoms =10 × 6.023 × 10²³ or 10N