Question

What is the total mass of 2.0 moles of h2(
g.??

Answer 1

When we speak of hydrogen, the assumption is that it is hydrogen gas, H2, and not atomic hydrogen. Since hydrogen is diatomic, 1 mol of H2 has a mass of 2.0 grams. Therefore, 2 moles will have a mass of 4.0 grams.

Likewise, 0.5 grams is 1/4 of the mass of 1 mole (2.0 g), so the answer is 0.25 mol H2.

You can even set up a conversion factor to get the answer.
0.5 g H2 x (1 mol H2 / 2.0 g H2) = 0.25 mol H2

Answer 2

The mass of 2 moles H2 would be 4 g.

From the formula:

  mole = mass/molar mass

Making mass the subject of the formula:

mass = mole x molar mass.

In this case, the mole of the H2 is 2 while the molar mass would also be 2 g/mol.

mass of 2 moles H2 = 2 x 2

                              = 4 g

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