Help needed I am stuck.... Moles help?

Question

What is the mass of 2.6 x 10^23 molecules of ammonia, NH3?

Answer 1

1 mole of NH3 contains 6.022x10^23 molecules
2.6 x 10^23 / 6.0 x 10^23 = 0.43 moles
1 mole of NH3 = 17 g
0.43 moles x 17 g/mole = 7.4 grams of NH3

Answer 2

Given: 2.6x10^23 molecules

Wanted: mass (grams is the unit)

Pathway: molecules --> moles --> grams

Conversion factors:

6.02x10^23 molecules = 1 mole

1 mole NH3 = 17 g NH3

2.6x10^23 molecules * (1mol/6.02x10^23 molecules) * (17g/mol) = 7.3 g NH3

Answer 3

For this you need to know Avogadro's Number. 6.022x10^23 (See link below) This tells you how many molecules are in one mole. Then you need to know the Molecular Weight of ammonia. MW = 17.03g/mol (See other link)

Now you just need to start with what you are given, and multiply by these conversion factors to cancel out your units and get where you want to be:

2.6x10^23 molec x mol/6.022x10^23 molec x 17.03g/mol = 7.35 grams of ammonia