Question

calculate the number of g-molecules in the following:

1. 2.45 g of sulphuric acid,H₂SO₄
2. 3.0115*10^24 molecules of SO₃
3. 1.2046*10^22 atoms of nitrogen
4. 16.8 L of oxygen gas at STP(1 atm & 0⁰
   

Answer 1

1)

1 mole of sulphuric acid, H₂SO₄= 6.023x10^23 molecules = 98 g, that is

98 g of sulphuric acid,H₂SO₄contains 6.023x10^23 molecules, therefore

2.45 g of sulphuric acid, H₂SO₄contains (2.45 x 6.023x10^23)/98 = 1.5 x 10^22 molecules.

2)

1 mole of sulphur trioxide, SO₃= 6.023x10^23 molecules = 80 g, that is

6.023x10^23 molecules of SO3 contains 80 g, therefore

3.0115*10^24 molecules of SO3 contains = (80 x 3.0115*10^24)/ 6.023x10^23

= 40 x 10 = 400 g.

3)

1 mole of nitrogen, N2 = 6.023x10^23 molecules = 14 g,

Each nitrogen molecule contains 2 atoms of nitrogen.

2 atoms of nitrogen = 6.023x10^23 molecules, then

1.2046*10^22 atoms of nitrogen = [(6.023x10^23)( 1.2046*10^22)]/2

= 3.63 x10^45 molecules

4)

At STP, 1L of oxygen O2 contains same number of molecules of oxygen that is 6.023x10^23 molecules

Therefore, 16.8 L of oxygen gas at STP contains = 16.8 x 6.023x10^23

= 101.2 x10^23 molecules