Q49 of 203 Page 174

How many grams of magnesium will have the same number of atoms as 6 grams of carbon? (Mg = 24 u; C = 12 u)

Given mass of carbon = 6g

Molar mass of carbon = 12g

No. of moles of carbon = Given mass of element/ Molar mass of element = 6g/12g = 0.5 moles

Equal number of moles of all the substances contain equal number of molecules.

So, 0.5 moles of carbon and 0.5 moles of magnesium contains same no. of molecules.

Hence, mass of 0.5 mole of magnesium = 0.5 × 24g = 12g

What weight of oxygen gas will contain the same number of molecules as 56 g of nitrogen gas? (O = 16 u; N = 14 u)

What mass of nitrogen, N2, will contain the same number of molecules as 1.8 g of water, H2O? (Atomic masses: N = 14 u; H = 1 u; O = 16 u)

If one gram of sulphur contains x atoms, calculate the number of atoms in one gram of oxygen element. (Atomic masses: S = 32 u; O = 16 u)

The mass of one atom of an element X is 2.0 × 10^-23 g.

(i) Calculate the atomic mass of element X.

(ii) What could element X be?