(Chemistry) Mass-to-Mole Conversion

Question

For the reaction C + 2H₂ → CH₄, how many moles of hydrogen are needed to make 152.5 grams of methane, CH₄ ?

Round your answer to the nearest tenth. If you answer is a whole number like 4, report the answer as 4.0

Use the following molar masses. If you do not use these masses, the computer will mark your answer incorrect.:



Element	Molar Mass
Hydrogen	1
Carbon	12

Answer 1

We want to work backwards and use the required mass of product methane to calculate the number of moles of hydrogen reactant needed. Stoichiometry relates the number of moles of reactants that produce products, so we should first convert the methane mass into moles.

M_CH4 = Molar mass of methane

C: 12 g/mole

H₄: 4*1 = 4 g/mol

CH₄:12+4 = 16 g/mol

n_{CH4, generated} = Number of moles of methane produced

n_{CH4, generated} = m_{CH4, generated} / M_CH4

= 152.5 g / 16 g/mol

= 9.5312 mol

Now we can relate the number of moles of hydrogen consumed to the number of moles of methane produced. The reaction equation provided shows that two moles of hydrogen are produced for each mole of methane produced. Therefore:

n_{H2, consumed} = n_{CH4, generated} * (2 H₂ / 1 CH₄)

= 9.5312 mol * 2/1

= 19.0624 mol

= 19.01 mol