Question

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What mass of H2 is needed to react with 8.75 g of O2 according to the following equation:
O2(g) + 4H2(g) → 2H2O(g)?

O 0.547 g H₂
O 2.21 g H₂
O 4.38 g H₂
O 17.5 g H₂

Answer 1

To solve this problem, we need to use stoichiometry and the balanced equation for the reaction. From the balanced equation, we see that 4 moles of H2 are required to react with 1 mole of O2 to produce 2 moles of H2O.

1 mole O2 = 32 g O2

8.75 g O2 = 8.75 g / 32 g/mol = 0.2734 moles O2

Using the stoichiometry of the balanced equation, we can determine the moles of H2 needed to react with the given moles of O2:

0.2734 moles O2 × 4 moles H2 / 1 mole O2 = 1.0936 moles H2

Finally, we can convert the moles of H2 to grams using the molar mass of H2:

1.0936 moles H2 × 2 g/mol H2 = 2.1872 g H2

Therefore, the mass of H2 needed to react with 8.75 g of O2 is approximately 2.19 g H2 (to two significant figures).

So, the closest option is O 2.21 g H₂.