Q1. calculate the number of moles of each substance in samples with the following masses:
a) 2.4 g of he
b) 250 mg of carbon
c) 15 g of sodium chloride
d) 40 g of sulphur
q2. calculate the mass in grams of each of the following samples:
a) 1.2 moles of k
b) 75 moles of h2
c) o.25 moles of steam
d) 0.15 mole of cuso4