How many grams are in 3.4x10^24 molecules of ammonia?

Remember:

6.022*10²³ molecules = 1 mol (Avogadro's number)

NH₃ = ammonia

To get molar mass of NH₃, add the mass of nitrogen + 3 times the mass of hydrogen (because there are 3 hydrogens in NH₃).

14.01 + 3 (1.01) = 17.04 grams NH₃ = molar mass

1) Set up your equation. You want to cancel out molecules, and get to grams through moles.

So multiply 3.4*10²⁴ molecules of ammonia * 1 mol of ammonia * 17.04 grams of ammonia and divide it by 6.022*10²³ molecules of ammonia and 1 mol of ammonia.

3.4*10²⁴ molecules of ammonia * 1 mol of ammonia * 17.04 grams of ammonia

6.022*10²³ molecules of ammonia 1 mol of ammonia

Your answer should come out to be: 96.20724 grams of ammonia

Round to 2 sig figs: 96 grams of ammonia