Chapter 3: Atoms and Molecules

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Atoms and Molecules

Question:

Q.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)?

Answer:

(a)- The molar mass of nitrogen is 14g. So, 1mole of nitrogen atoms weigh 14g.

Therefore, the mass of 1 mole of nitrogen atom is 14 g.

 

(b)- The molar mass of aluminium atom is 27g. This means that the mass of 1 mole of aluminium atom will be 27g.

mathbf{Mass of 4 moles of aluminium atom =(frac { 27g }{ 1 mol } 	imes 4 mol=108g)}

 

Therefore, the mass of 4 moles of aluminum atom is 108 g.

 

(c)- The sodium sulphite (Na2SO3)contains sodium, sulphur, and oxygen atoms. The gram atomic mass of sodium is 23g, sulphur is 32g, and oxygen is 16g.

So, the Molar mass of Na2SO3 = 2(Atomic mass of Na) + Atomic mass of s + 3(Atomic mass of O)

= 2(23g) +32g + 3(16g) = 126g

This means that the mass of one mole of Na2SO3 is 126g.

mathbf{Mass of 10 moles of sodium sulphite =(frac { 126g }{ 1 mol } 	imes 10 mol=1260g)}

 

Therefore, the mass of 10 moles of sodium sulphite is 1260g


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