Monday, October 15, 2007

Chemistry Questions - Mole Concepts

A Chemistry Question that was posed by a local singapore student that is taking her O level this year.

Which of the following consists of the greatest number of atoms?
A. 4g of hydrogen gas, H2
B. 48g of solid magnesium, Mg
C. 71g of chlorine has, Cl2
D. 24 dm3 of argon gas, Ar at r.t.p.

Any takers??

Learning Experience with A Difference


illuminate-x said...

I'm thinking it's A...

No. of moles of H2 = 4/2 = 2 mol
No. of moles of Mg = 48/24 = 2 mol
No. of moles of Cl2 = 71/71 = 1 mol
No. of moles of Ar = 24/24 = 1 mol

We can rule out C and D, which leaves A and B - H2 obviously has more atoms than Mg, which leaves us with A ;D not very sure about this...

Cheney said...

hmm. i think it's A too.

not really sure, but since the avogadro constant states that '1 mol = amount of substance which contains 6.02 x 10^23 particles, where particles may refer to atoms, molecules, charges, ions or electrons', then 2 mol of hydrogen gas probably contains 6.02 x 10^23 x 2 x 2 atoms, which magnesium only contains 6.02 x 10^23 x 2. This is because hydrogen is diatomic. or something like that. roughly la : )

Spirit-Breaker said...

A or B.
I worked out for A and B and I got 2 moles.
For C and D it is out because I got 1 mole.
I'm not too sure...

Sean Chua said...

Well Done!

Cheney answers is closest for his explaination.

This is indeed have to do with Avogadro's constant.

Trick for this question is to pick up the fact that they are asking for ATOMS. H2 gas molecule has two atoms.

"Learning Experience with A Difference"