Q1. Calculate the number of atoms in
a) 0.5 mole atoms of nitrogen
b) 0.2 mole moleules of nitrogen
c) 3.2g of sulphur
d)3.4 g of H2S
Q2. how many molecules of water of hydration are present in 252 mg of oxalic acid?
1) (a) 1 mole of nitrogen atoms = 6.022 1023 atoms
0.5 moles of Nitrogen atoms = 6.022 1023 0.5 = 3.0111023 atoms
(b) 1 mole of nitrogen molecules = 6.022 1023 molecules
0.2 moles of nitrogen molecules = 6.022 1023 0.2 = 1.20441023 molecules
As 1 molecule of nitrogen contains 2 atoms of nitrogen.
So, 1.20441023 molecules of nitrogen will contain 1.20441023 2 atoms
= 2.4088 1023 atoms
(c) 32 g of sulphur (Molar mass of Sulphur ) = 6.022 1023 atoms
3.2 g of sulphur =
= 0.6022 1023 atoms
(d) 3.4 g of H2S
Molar mass of H2S = 34 g mol-1
34 g of H2S contains 6.0221023 molecules
1 molecule of H2S contain 2 atom of hydrogen and 1 atom of sulphur.
34 g of H2S contain 26.0221023 atoms of hydrogen and 6.0221023 atoms of Sulphur.
3.4 g of H2S contain 12.0441022 atoms of hydrogen and 6.0221023 atoms of sulphur.
2) Molecular formula of oxalic acid is H2C2O4.2H2O
and molar mass of oxalic acid = gmol-1
water molecule in 1 mole oxalic acid = 2 molecules
So, 126 g of oxalic acid contains 2 6.022 1023 molecules of water.
thus, 0.252 g of oxalic acid will contain =
= 2.409 1021 molecules of water
0.5 moles of Nitrogen atoms = 6.022 1023 0.5 = 3.0111023 atoms
(b) 1 mole of nitrogen molecules = 6.022 1023 molecules
0.2 moles of nitrogen molecules = 6.022 1023 0.2 = 1.20441023 molecules
As 1 molecule of nitrogen contains 2 atoms of nitrogen.
So, 1.20441023 molecules of nitrogen will contain 1.20441023 2 atoms
= 2.4088 1023 atoms
(c) 32 g of sulphur (Molar mass of Sulphur ) = 6.022 1023 atoms
3.2 g of sulphur =
= 0.6022 1023 atoms
(d) 3.4 g of H2S
Molar mass of H2S = 34 g mol-1
34 g of H2S contains 6.0221023 molecules
1 molecule of H2S contain 2 atom of hydrogen and 1 atom of sulphur.
34 g of H2S contain 26.0221023 atoms of hydrogen and 6.0221023 atoms of Sulphur.
3.4 g of H2S contain 12.0441022 atoms of hydrogen and 6.0221023 atoms of sulphur.
2) Molecular formula of oxalic acid is H2C2O4.2H2O
and molar mass of oxalic acid = gmol-1
water molecule in 1 mole oxalic acid = 2 molecules
So, 126 g of oxalic acid contains 2 6.022 1023 molecules of water.
thus, 0.252 g of oxalic acid will contain =
= 2.409 1021 molecules of water