Hydrogen burns in oxygen according to 2 H2 + O2 -> 2 H2O. How many grams of water form when 10 g of hydrogen (H2, 2 g/mol) react completely? (H2O is 18 g/mol)
Answer and explanation
Correct answer: B. 90 g
- Step 1: Moles of H2 = 10 / 2 = 5 mol, and the ratio H2 : H2O is 1 : 1.
- Step 2: Mass of water = 5 x 18 = 90 g.
Answer
90 g.
Why not the others: The mole ratio is 2 to 2, so one mole of water forms per mole of hydrogen; the other values ignore the molar masses or the mole ratio.
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