1) Which of the following represents one mole of oxygen gas? a) 16 g of O b) 16 g of O₂ c) 32 g of O₂ d) 22.4 cm³ of O₂ 2) The relative molecular mass (Mr) of calcium carbonate, CaCO₃, is: a) 40 b) 44 c) 60 d) 100 3) Which statement about one mole of any gas is correct? a) It occupies 24 dm³ at 25°C and 1 atm. b) It occupies 24 cm³ at room conditions. c) It contains 6.02 × 10²² molecules. d) Its mass is always 1 g. 4) How many moles of water molecules are present in 36 g of H₂O? a) . 0.5 mol b) 1 mol c) 2 mol d) 3 mol 5) What mass of magnesium oxide is formed when 6 g of magnesium reacts completely with oxygen? (Mr of MgO = 40, Ar: Mg = 24, O = 16) a) 6g b) 8g c) 10g d) 15g 6) Which of the following gives the correct ratio of atoms in aluminum sulfate, Al₂(SO₄)₃? a) 2 Al : 3 S : 12 O b) 1 Al : 1 S : 4 O c) 2 Al : 3 S : 4 O d) 1 Al : 3 S : 12 O 7) What is the empirical formula of a compound that contains 80% carbon and 20% hydrogen by mass? a) CH b) CH₂ c) C₂H₄ d) CH₄ 8) When 2 g of hydrogen react with 16 g of oxygen, how many grams of water are formed? (Equation: 2H₂ + O₂ → 2H₂O) a) 9g b) 18g c) 20g d) 36g 9) What volume of carbon dioxide (CO₂) is formed when 1 mole of methane burns completely at room temperature and pressure? a) 11.2 dm³ b) 22.4 dm³ c) 24 dm³ d) 48 dm³ 10) A sample of calcium carbonate decomposes on heating: CaCO₃ → CaO + CO₂ If 10 g of CaCO₃ produces 4.4 g of CO₂, what is the percentage yield? (Mr: CaCO₃ = 100, CO₂ = 44) a) 50% b) 75% c) 90% d) 100%

Stoichiometry

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