Question

Question 7 What is the mass of−−
(a) 1 mole of nitrogen atoms?
(b) 4 moles of aluminium atoms (Atomic mass of aluminium = 27)?
(c) 10 moles of sodium sulphite (Na2SO3)?

Class 9 - Science - Atoms and Molecules Page 44

Answer 1

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Here is your answer ==============================================================================

>> (a) Mass of 1 mole of = Atomic mass of nitrogen
nitrogen atoms (N) expressed in grams
= 14 g

(b) The atomic mass of aluminum is given to be 27 u. This means that 1 mole of aluminium atoms has a mass of 27 grams.

Now , 1 mole of aluminium atoms = 27 g
= 27 × 4 g
= 108 g

(c) Mass of 1 mole of sodium sulphite = Molecular mass of sodium sulphite (Na2SO3) in grams
= Mass of 2Na + Mass of S + Mass of 3 'O'
= 2×23 + 32 + 3 × 16
= 46 + 32 + 48
= 126 g

So, Mass of 10 moles of = 126 × 10 g
sodium sulphite = 1260 g

Answer 2

Mass of 1 mole of nitrogen atoms = Atomic mass of nitrogen atom

Atomic mass of nitrogen atom = 14u

Therefore, Mass of 1 mole of nitrogen atoms = 14 g

(b) Mass of 1 mole of Aluminium atoms = Atomic mass of Aluminium

Atomic mass of Aluminium = 27 u

Mass of 1 mole of aluminium atom = 27 g

Therefore, mass of 4 moles of aluminium atoms = 4 X 27 = 108 g

(c) Mass of 1 mole of sodium sulphite = Molecular mass of sodium sulphite (Na2SO3) in grams

Molecular mass of Na2SO3 in grams = Mass of 2Na + Mass of S +Mass of 3 '0'

= 2 X 23 + 32 + 3 X 16

= 46 + 32 + 48

= 126 g

Therefore, Mass of 10 moles of Na2SO3 = 126 x 10 g = 1260 g