# Stoichiometry problems and solutions

1. What is the stoichiometric coefficient of Oxygen (O₂) in the combustion of Methane (CH₄)? Solution: The stoichiometric coefficient of Oxygen in the combustion of Methane is 2. (CH₄ + 2O₂ → CO₂ + 2H₂O)

2. What mass of Oxygen (O₂) is needed to completely combust 16 g of Methane (CH₄)? Solution: The molar mass of CH₄ is 16 g/mol and that of O₂ is 32 g/mol. As per the balanced equation, one mole of CH₄ requires two moles of O₂. Hence, 16 g of CH₄ requires 2 x 32 g = 64 g of O₂.
3. How many moles of Water (H₂O) are produced from the complete combustion of 2 moles of Hydrogen (H₂)? Solution: According to the balanced equation, 2 moles of H₂ react with 1 mole of O₂ to produce 2 moles of H₂O. Therefore, 2 moles of Hydrogen produce 2 moles of Water.
4. What mass of Sodium Chloride (NaCl) is formed from the reaction of 23 g of Sodium (Na) with excess Chlorine (Cl₂)? Solution: The molar mass of Na is 23 g/mol and that of NaCl is 58.5 g/mol. As per the balanced equation, one mole of Na produces one mole of NaCl. Hence, 23 g of Na produces 58.5 g of NaCl.
5. How many grams of Carbon Dioxide (CO₂) are formed from the combustion of 128 g of Butane (C₄H₁₀)? Solution: The molar mass of C₄H₁₀ is 58.1 g/mol and that of CO₂ is 44 g/mol. The balanced equation indicates that 2 moles of C₄H₁₀ react to form 8 moles of CO₂. Hence, 128 g of C₄H₁₀ (approximately 2.2 moles) produce about 2.2 x 8 x 44 g = 774.4 g of CO₂.
6. How many moles of Ammonia (NH₃) can be produced from 28 g of Nitrogen (N₂)? Solution: The molar mass of N₂ is 28 g/mol. According to the balanced equation, one mole of N₂ produces two moles of NH₃. Hence, 28 g of N₂ can produce 2 moles of NH₃.
7. What volume of Hydrogen gas (H₂) at STP is produced from the reaction of 54 g of Aluminum (Al) with excess Hydrochloric Acid (HCl)? Solution: The molar mass of Al is 27 g/mol. As per the balanced equation, 2 moles of Al react to produce 3 moles of H₂. Hence, 54 g of Al (2 moles) produces 3 x 2 = 6 moles of H₂. At STP, one mole of gas occupies 22.4 L. Therefore, 6 moles occupy 6 x 22.4 L = 134.4 L.
8. How many grams of Water (H₂O) are formed from the reaction of 18 g of Hydrogen (H₂) with excess Oxygen (O₂)? Solution: The molar mass of H₂ is 2 g/mol and that of H₂O is 18 g/mol. According to the balanced equation, 2 moles of H₂ react to produce 2 moles of H₂O. Hence, 18 g of H₂ (9 moles) produces 9 x 18 g = 162 g of H₂O.
9. How many moles of Sodium Hydroxide (NaOH) are needed to neutralize 98 g of Sulfuric Acid (H₂SO₄)? Solution: The molar mass of H₂SO₄ is 98 g/mol. According to the balanced equation, 2 moles of NaOH are required to neutralize 1 mole of H₂SO₄. Hence, 98 g of H₂SO₄ (1 mole) requires 2 moles of NaOH.
10. What mass of Calcium Oxide (CaO) is formed from the decomposition of 100 g of Calcium Carbonate (CaCO₃)? Solution: The molar mass of CaCO₃ is approximately 100 g/mol and that of CaO is 56 g/mol. According to the balanced equation, one mole of CaCO₃ produces one mole of CaO. Hence, 100 g of CaCO₃ produces 56 g of CaO.
11. How many grams of Copper (Cu) can be obtained from the reaction of 63.5 g of Copper (II) Oxide (CuO) with Hydrogen (H₂)? Solution: The molar mass of CuO is 79.5 g/mol and that of Cu is 63.5 g/mol. According to the balanced equation, one mole of CuO produces one mole of Cu. Hence, 63.5 g of CuO produces 63.5 g of Cu.
12. What volume of Carbon Dioxide (CO₂) at STP is produced from the combustion of 46 g of Ethanol (C₂H₅OH)? Solution: The molar mass of C₂H₅OH is 46 g/mol. According to the balanced equation, one mole of C₂H₅OH produces two moles of CO₂. Hence, 46 g of C₂H₅OH (1 mole) produces 2 x 22.4 L = 44.8 L of CO₂ at STP.
13. How many moles of Water (H₂O) are produced from the reaction of 2 moles of Hydrogen Peroxide (H₂O₂)? Solution: According to the balanced equation, two moles of H₂O₂ react to produce two moles of H₂O. Hence, 2 moles of H₂O₂ produce 2 moles of H₂O.
14. What mass of Potassium Chloride (KCl) is formed from the reaction of 39 g of Potassium (K) with excess Chlorine (Cl₂)? Solution: The molar mass of K is 39 g/mol and that of KCl is 74.5 g/mol. As per the balanced equation, one mole of K produces one mole of KCl. Hence, 39 g of K produces 74.5 g of KCl.
15. How many moles of Sodium Chloride (NaCl) are formed from the reaction of 1 mole of Sodium Hydroxide (NaOH) with Hydrochloric Acid (HCl)? Solution: According to the balanced equation, one mole of NaOH reacts with one mole of HCl to produce one mole of NaCl. Therefore, 1 mole of NaOH produces 1 mole of NaCl.
16. How many grams of Nitrogen (N₂) can be produced from the reaction of 70 g of Ammonium Nitrite (NH₄NO₂)? Solution: The molar mass of NH₄NO₂ is 64 g/mol and that of N₂ is 28 g/mol. According to the balanced equation, one mole of NH₄NO₂ produces one mole of N₂. Hence, 70 g of NH₄NO₂ (approximately 1.1 moles) produces about 1.1 x 28 g = 30.8 g of N₂.
17. How many moles of Hydrogen gas (H₂) are produced from the reaction of 27 g of Aluminum (Al) with excess Sulfuric Acid (H₂SO₄)? Solution: The molar mass of Al is 27 g/mol. As per the balanced equation, 2 moles of Al react with 3 moles of H₂SO₄ to produce 3 moles of H₂. Hence, 27 g of Al (1 mole) produces 1.5 moles of H₂.
18. What volume of Oxygen gas (O₂) at STP is needed for the complete combustion of 1 mole of Propane (C₃H₈)? Solution: According to the balanced equation, one mole of C₃H₈ reacts with five moles of O₂. Therefore, 5 x 22.4 L = 112 L of O₂ is required.
19. How many grams of Sodium Bicarbonate (NaHCO₃) are formed from the reaction of 40 g of Sodium Hydroxide (NaOH) with excess Carbon Dioxide (CO₂)? Solution: The molar mass of NaOH is 40 g/mol and that of NaHCO₃ is 84 g/mol. According to the balanced equation, one mole of NaOH reacts with one mole of CO₂ to produce one mole of NaHCO₃. Hence, 40 g of NaOH produces 84 g of NaHCO₃.
20. How many moles of Sulfur Trioxide (SO₃) are formed from the reaction of 64 g of Sulfur Dioxide (SO₂) with Oxygen (O₂)? Solution: The molar mass of SO₂ is 64 g/mol. According to the balanced equation, 2 moles of SO₂ react with 1 mole of O₂ to produce 2 moles of SO₃. Hence, 64 g of SO₂ (1 mole) produces 1 mole of SO₃.