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1.BASIC CONCEPTS eLearn.Punjab

Example (6):

Calculate the gram atoms (moles) in
(a) 0.1 g of sodium.
(b) 0.1 kg of silicon.

Solution

(a) No. of gram atoms = Mass of element in gram
Molar mass

Mass of sodium = 0.1 g
Molar mass = 23 g/mol

Number of gram atoms of sodium = 0.1g = 0.0043 mol
23 gmol−1

= 4.3 x 10-3 mol Answer

(b) First of all convert the mass of silicon into grams.

Mass of silicon = 0.1 kg = 0.1 x 1000 = 100 g

Molar mass = 28.086 gmol-1

Number of gram atoms of silicon = 100 g = 3.56 moles Answer
28.086 gmol−1

Example (7):

Calculate the mass of 10-3 moles of MgSO4.

Solution:

MgSO4 is an ionic compound. We will consider its formula mass in place of molecular mass.

Number of gram formula or mole of a substance = Mass of the ionic substance

Formula mass of the ionic substance

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