Which of the following has the greatest mass?

Question

1.0 mole of C atoms
1.0 mole of water molecules
2.0 moles of H2 molecules
0.5 mole of Kr atoms

Answer 1

moles = mass/Mr

therefore mass = moles x Mr

so...
1) 1.0 moles of C atoms has a mass of 1 x 12 =12g
2) 1.0 moles of H2O has a mass of 1 x (16 + 2) = 18g
3) 2.0 moles of H2 has a mass of 2 x 1 = 2g
4) 0.5 moles of Kr has a mass of 0.5 x 84 = 42g

so 0.5 moles of Kr atoms has the greatest mass.

Answer 2

1 mol C = 12 g
1 mol H2O = 18g
2 mol H2 = 4 g
0.5 mol Kr = 41.9 g

I assume you can do the reast of the work from there. I used a periodic table and some simple multiplication and addition to figure out this part.

Answer 3

start by looking up the moleculair weight of those substances.
Or in this case, let me look it up ;-)

1 mol of C = 12.08 gr
1 mol of H20 = 18.008 gr
1 mol of H2 = 2.008 gr
1 mol of Kr = 83.798 gr

I think you can do the rest yourself...