BMST - Basic Math and Science Chemical Reactions and Stoichiometry Questions and Answers 3 — Questions and Answers
Question 1: In the reaction 2H₂ + O₂ → 2H₂O, how many moles of water are produced from 4 moles of H₂?
- 2 moles
- 4 moles (Correct answer)
- 6 moles
- 8 moles
Correct answer: 4 moles
The molar ratio of H₂ to H₂O is 1:1, so 4 moles of H₂ produces 4 moles of H₂O.
Question 2: Which type of chemical reaction involves a single compound breaking down into two or more simpler substances?
- Synthesis
- Single replacement
- Decomposition (Correct answer)
- Combustion
Correct answer: Decomposition
Decomposition reactions break one compound into two or more simpler substances (e.g., 2H₂O → 2H₂ + O₂).
Question 3: What is the molar mass of glucose (C₆H₁₂O₆)?
- 120 g/mol
- 150 g/mol
- 180 g/mol (Correct answer)
- 210 g/mol
Correct answer: 180 g/mol
Molar mass = 6(12) + 12(1) + 6(16) = 72 + 12 + 96 = 180 g/mol.
Question 4: In a double replacement reaction between NaCl and AgNO₃, which precipitate forms?
- NaNO₃
- AgCl (Correct answer)
- NaAg
- ClNO₃
Correct answer: AgCl
AgCl is insoluble in water and precipitates out of solution in this double replacement reaction.
Question 5: How many grams of CO₂ (molar mass 44 g/mol) are produced when 0.5 moles of CO₂ are generated?
- 11 g
- 22 g (Correct answer)
- 44 g
- 88 g
Correct answer: 22 g
Mass = moles × molar mass = 0.5 mol × 44 g/mol = 22 g.
Question 6: Which of the following is an example of a combustion reaction?
- NaOH + HCl → NaCl + H₂O
- CH₄ + 2O₂ → CO₂ + 2H₂O (Correct answer)
- Zn + CuSO₄ → ZnSO₄ + Cu
- 2KClO₃ → 2KCl + 3O₂
Correct answer: CH₄ + 2O₂ → CO₂ + 2H₂O
Combustion reactions involve a hydrocarbon reacting with oxygen to produce CO₂ and H₂O.
Question 7: If you have 90 g of water (molar mass 18 g/mol), how many moles of water do you have?
- 2 moles
- 3 moles
- 4 moles
- 5 moles (Correct answer)
Correct answer: 5 moles
Moles = mass / molar mass = 90 g ÷ 18 g/mol = 5 moles.
BMST - Basic Math and Science Chemical Reactions and Stoichiometry Questions and Answers 3
In the reaction 2H₂ + O₂ → 2H₂O, how many moles of water are produced from 4 moles of H₂?