This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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When 4.0 g of H2 reacts completely with excess O2, 36 g of H2O is produced. Worked Solution: 1. Calculate the molar masses: Molar mass of H2 = 2 (1.008 g/mol) = 2.016 g/mol Molar mass of H2O = (2 1.008 g/mol) + (15.999 g/mol) = 18.015 g/mol 2. Convert the mass of H2 to moles: Moles of H2 = Mass of H2 / Molar mass of H2 Moles of H2 = 4.0 g / 2.016 g/mol = 1.984 mol H2 3. Use the mole ratio from the balanced equation to find moles of H2O: The balanced equation is 2 H2 + O2 -> 2 H2O. From the equation, 2 moles of H2 produce 2 moles of H2O. The mole ratio is 1:1. Moles of H2O = Moles of H2 * (2 mol H2O / 2 mol H2) Moles of H2O = 1.984 mol H2 * (1 mol H2O / 1 mol H2) = 1.984 mol H2O 4. Convert moles of H2O to mass: Mass of H2O = Moles of H2O * Molar mass of H2O Mass of H2O = 1.984 mol * 18.015 g/mol = 35.744 g 5. Round to appropriate significant figures: The given mass (4.0 g H2) has two significant figures. Therefore, the answer should also be rounded to two significant figures. Mass of H2O = 36 g