Question

Mass in kg of k2o containing the same number of of moles of k atoms as are present in 1 kg of kcl

Answer 1

Mass of KCl = 1 Kg = 1000g
Molecular weight of KCl = 39 + 35.5 = 74.5 g/mol
∴mole of KCl = given weight/molecular weight
= 1000/74.5

∵ 1 mole of KCl contains 1 mole of K
∴ 1000/74.5 moles of KCl contain 1000/74.5 moles of K

∴ mole of K in KCl = 1000/74.5
A/C to question,
mole of K in K₂O = mole of K in KCl = 1000/74.5
But we see that, 1 mole of K₂O contains 2 moles of K
∴ 500/74.5 moles of K₂O contain 1000/74.5 moles of K

So, finally number of mole of K₂O = 500/74.5
weight of K₂O = number of mole × molecular weight
= 500/74.5 × (39 × 2 + 16)
= 500/74.5 × 94
= 47000/74.5 g = 47/74.5 kg
= 0.63 kg

Answer 2

Given, Mass of KCl = 1 Kg = 1000g
We know, Molecular weight of KCl = 39 + 35.5 = 74.5 g/mol

1 mole of KCl will have 1 mole of K

So,mole of K in KCl = 1000/74.5

Given that,
mole of K in K₂O = mole of K in KCl = 1000/74.5

1 mole of K₂O contains 2 moles of K
So, 500/74.5 moles of K₂O contain 1000/74.5 moles of K


No of mole of K₂O = 500/74.5
= 500/74.5 × (39 × 2 + 16) = 47/74.5 kg
= 0.63 kg