“Stoichiometry” MCQ with Answer Explanation.

Here some basic mcq’s about “stoichiometry” with answer which is explained in details. Let’s check one by one which is given below.

1. What is the molar mass of water (H₂O)?

A) 18 g/mol
B) 16 g/mol
C) 20 g/mol
D) 22 g/mol

Answer: A) 18 g/mol

Explanation: The molar mass of water is calculated as follows: H (1 g/mol) × 2 + O (16 g/mol) = 2 + 16 = 18 g/mol.

2. In the reaction 2H₂ + O₂ → 2H₂O, how many moles of H₂ are needed to completely react with 1 mole of O₂?

A) 1 mole
B) 2 moles
C) 3 moles
D) 4 moles

Answer: B) 2 moles

Explanation: According to the balanced equation, 2 moles of H₂ are required for every 1 mole of O₂.

3. What is the mass of 0.5 moles of sodium chloride (NaCl)? (Molar mass of NaCl = 58.5 g/mol)

A) 29.25 g
B) 58.5 g
C) 100 g
D) 117 g

Answer: A) 29.25 g

Explanation: Mass = moles × molar mass = 0.5 moles × 58.5 g/mol = 29.25 g.

4. If 3 moles of A react with 2 moles of B to form 4 moles of C, what is the stoichiometric ratio of A to C?

A) 3:4
B) 4:3
C) 2:3
D) 3:2

Answer: A) 3:4

Explanation: The reaction shows that 3 moles of A produce 4 moles of C, leading to a ratio of 3:4.

5. Which of the following statements is true about a limiting reactant?

A) It is always the reactant with the lowest molar mass.
B) It determines the amount of product formed.
C) It is completely consumed in the reaction.
D) Both B and C are correct.

Answer: D) Both B and C are correct.

Explanation: The limiting reactant is the one that runs out first, thus limiting the amount of product formed and is completely consumed during the reaction.

6. How many grams of CO₂ are produced when 10 g of glucose (C₆H₁₂O₆) are completely burned? (Molar mass of CO₂ = 44 g/mol)

A) 44 g
B) 88 g
C) 132 g
D) 176 g

Answer: B) 88 g

Explanation: The balanced equation for glucose combustion is C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O. From 1 mole of glucose, 6 moles of CO₂ are produced. The molar mass of glucose is 180 g/mol. Thus, 10 g of glucose produces (10 g / 180 g/mol) × 6 moles of CO₂ = 0.333 moles of CO₂, which is 0.333 moles × 44 g/mol = 14.67 g.

7. In a chemical reaction, if 4 moles of reactant A yield 8 moles of product B, what is the yield of B if 2 moles of A are used?

A) 2 moles
B) 4 moles
C) 6 moles
D) 8 moles

Answer: B) 4 moles

Explanation: The stoichiometry shows that 4 moles of A yield 8 moles of B. Thus, using 2 moles of A would yield (2 moles A) × (8 moles B / 4 moles A) = 4 moles of B.

8. What volume of 0.5 M HCl is required to neutralize 0.1 moles of NaOH? (Assume complete neutralization)

A) 100 mL
B) 200 mL
C) 400 mL
D) 500 mL

Answer: B) 200 mL

Explanation: The reaction between HCl and NaOH is 1:1. Therefore, to neutralize 0.1 moles of NaOH, 0.1 moles of HCl are required. Volume = moles / concentration = 0.1 moles / 0.5 M = 0.2 L or 200 mL.

9. What is the percentage yield if 10 g of product is obtained from 20 g of theoretical yield?

A) 50%
B) 75%
C) 100%
D) 125%

Answer: A) 50%

Explanation: Percentage yield = (actual yield / theoretical yield) × 100 = (10 g / 20 g) × 100 = 50%.

10. In the reaction N₂ + 3H₂ → 2NH₃, how many grams of NH₃ can be produced from 5 moles of H₂? (Molar mass of NH₃ = 17 g/mol)

A) 85 g
B) 34 g
C) 68 g
D) 51 g

Answer: C) 34 g

Explanation: 3 moles of H₂ produce 2 moles of NH₃. Therefore, 5 moles of H₂ can produce (5 moles H₂) × (2 moles NH₃ / 3 moles H₂) = 3.33 moles of NH₃. The mass of NH₃ produced = 3.33 moles × 17 g/mol = 56.61 g.

11. What is the molar mass of carbon dioxide (CO₂)?

A) 44 g/mol
B) 22 g/mol
C) 30 g/mol
D) 18 g/mol

Answer: A) 44 g/mol

Explanation: Molar mass = C (12 g/mol) + O (16 g/mol) × 2 = 12 + 32 = 44 g/mol.

12. How many moles of O₂ are needed to completely react with 4 moles of C₃H₈ in the reaction C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O?

A) 5 moles
B) 10 moles
C) 15 moles
D) 20 moles

Answer: B) 10 moles

Explanation: The reaction shows that 1 mole of C₃H₈ reacts with 5 moles of O₂. Thus, 4 moles of C₃H₈ require 4 × 5 = 20 moles of O₂.

13. What is the empirical formula of a compound with a molecular formula C₆H₁₂O₆?

A) C₃H₆O₃
B) C₆H₁₂O₆
C) C₂H₄O₂
D) CH₂O

Answer: D) CH₂O

Explanation: The empirical formula is obtained by dividing the subscripts by their greatest common divisor (GCD), which is 6 in this case.

14. If 2 moles of sodium react with chlorine gas to produce sodium chloride, how many grams of sodium chloride can be produced? (Molar mass of NaCl = 58.5 g/mol)

A) 58.5 g
B) 117 g
C) 175.5 g
D) 235 g

Answer: B) 117 g

Explanation: 2 moles of Na produce 2 moles of NaCl. Mass of NaCl = 2 moles × 58.5 g/mol = 117 g.

15. In the reaction 4Fe + 3O₂ → 2Fe₂O₃, what is the mole ratio of Fe to O₂?

A) 4:3
B) 2:3
C) 3:4
D) 2:1

Answer: A) 4:3

Explanation: The balanced equation shows that 4 moles of Fe react with 3 moles of O₂, giving a ratio of 4:3.

16. How many grams of aluminum are required to produce 54 grams of aluminum oxide (Al₂O₃)? (Molar mass of Al = 27 g/mol, Al₂O₃ = 102 g/mol)

A) 27 g
B) 54 g
C) 81 g
D) 108 g

Answer: C) 81 g

Explanation: From the reaction 4Al + 3O₂ → 2Al₂O₃, 2 moles of Al₂O₃ require 4 moles of Al. Therefore, 54 g Al₂O₃ (0.529 moles) require 0.529 × 4 = 2.116 moles of Al, which equals 2.116 × 27 g/mol = 57 g.

17. If you have 6 moles of CaCO₃, how many moles of CO₂ are produced when it decomposes? (CaCO₃ → CaO + CO₂)

A) 3 moles
B) 6 moles
C) 9 moles
D) 12 moles

Answer: B) 6 moles

Explanation: The decomposition of 1 mole of CaCO₃ produces 1 mole of CO₂. Thus, 6 moles produce 6 moles of CO₂.

18. What is the mass of 3 moles of potassium bromide (KBr)? (Molar mass of KBr = 119 g/mol)

A) 297 g
B) 357 g
C) 357 g
D) 437 g

Answer: A) 357 g

Explanation: Mass = moles × molar mass = 3 moles × 119 g/mol = 357 g.

19. In the balanced equation N₂ + 3H₂ → 2NH₃, how many grams of nitrogen are needed to produce 68 g of ammonia (NH₃)? (Molar mass of NH₃ = 17 g/mol)

A) 14 g
B) 28 g
C) 42 g
D) 56 g

Answer: B) 28 g

Explanation: 68 g of NH₃ equals 4 moles (68 g / 17 g/mol). From the equation, 1 mole of N₂ produces 2 moles of NH₃, thus 2 moles of N₂ are needed, which is 2 × 28 g = 28 g.

20. What volume of 0.2 M NaOH is needed to completely neutralize 0.5 moles of H₂SO₄?

A) 250 mL
B) 500 mL
C) 750 mL
D) 1000 mL

Answer: C) 750 mL

Explanation: The reaction is H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O. To neutralize 0.5 moles of H₂SO₄, 1 mole of NaOH is required. Thus, 0.5 moles H₂SO₄ require 1 mole of NaOH, and volume = 1 mole / 0.2 M = 5 L = 750 mL.

21. In a reaction where 2 moles of A react with 3 moles of B to produce 4 moles of C, if 1.5 moles of A are used, how many moles of C are produced?

A) 2 moles
B) 3 moles
C) 4 moles
D) 6 moles

Answer: B) 3 moles

Explanation: The ratio of A to C is 2:4, or 1:2. Therefore, 1.5 moles of A produce 1.5 × 2 = 3 moles of C.

22. How many grams of H₂ are produced from the electrolysis of water? If 18 g of water are decomposed. (Molar mass of H₂ = 2 g/mol)

A) 4 g
B) 6 g
C) 8 g
D) 12 g

Answer: B) 6 g

Explanation: 18 g of water equals 1 mole (18 g / 18 g/mol). From the decomposition of water, 1 mole of water produces 2 moles of H₂, which equals 2 × 2 g/mol = 4 g.

23. In the reaction 2Mg + O₂ → 2MgO, how many grams of magnesium oxide (MgO) can be produced from 3 moles of magnesium? (Molar mass of MgO = 40 g/mol)

A) 40 g
B) 60 g
C) 80 g
D) 120 g

Answer: C) 120 g

Explanation: From the equation, 2 moles of Mg produce 2 moles of MgO. Therefore, 3 moles of Mg will produce 3 moles of MgO. Mass = 3 moles × 40 g/mol = 120 g.

24. What is the number of molecules in 1 mole of a substance?

A) 6.022 × 10²²
B) 6.022 × 10²³
C) 6.022 × 10²⁴
D) 6.022 × 10²⁵

Answer: B) 6.022 × 10²³

Explanation: Avogadro’s number states that 1 mole of any substance contains 6.022 × 10²³ molecules.

25. If you have 4 moles of H₂ and 2 moles of O₂, how many moles of water (H₂O) can be produced?

A) 2 moles
B) 4 moles
C) 6 moles
D) 8 moles

Answer: B) 4 moles

Explanation: The reaction is 2H₂ + O₂ → 2H₂O. Therefore, 4 moles of H₂ can produce 4 moles of H₂O with 2 moles of O₂.

26. In the reaction C + O₂ → CO₂, how many grams of carbon are needed to produce 88 g of CO₂? (Molar mass of CO₂ = 44 g/mol, C = 12 g/mol)

A) 12 g
B) 24 g
C) 36 g
D) 48 g

Answer: B) 24 g

Explanation: 88 g of CO₂ equals 2 moles (88 g / 44 g/mol). From the balanced equation, 1 mole of C produces 1 mole of CO₂, so 2 moles of C are needed, which equals 2 × 12 g/mol = 24 g.

27. What is the mass of 5 moles of sulfuric acid (H₂SO₄)? (Molar mass of H₂SO₄ = 98 g/mol)

A) 490 g
B) 500 g
C) 540 g
D) 560 g

Answer: A) 490 g

Explanation: Mass = moles × molar mass = 5 moles × 98 g/mol = 490 g.

28. In the equation 2Na + Cl₂ → 2NaCl, what is the mass of sodium chloride produced from 2 moles of sodium? (Molar mass of NaCl = 58.5 g/mol)

A) 58.5 g
B) 117 g
C) 234 g
D) 350 g

Answer: B) 117 g

Explanation: 2 moles of Na produce 2 moles of NaCl. Therefore, the mass of NaCl = 2 × 58.5 g/mol = 117 g.

29. How many moles of NaOH are needed to neutralize 1 mole of HCl?

A) 0.5 moles
B) 1 mole
C) 2 moles
D) 3 moles

Answer: B) 1 mole

Explanation: The neutralization reaction is HCl + NaOH → NaCl + H₂O, which shows a 1:1 ratio.

30. If 0.5 moles of Al react with O₂, how many moles of Al₂O₃ are formed? (4Al + 3O₂ → 2Al₂O₃)

A) 0.25 moles
B) 0.5 moles
C) 1 mole
D) 2 moles

Answer: A) 0.25 moles

Explanation: The reaction shows that 4 moles of Al produce 2 moles of Al₂O₃. Thus, 0.5 moles of Al will produce 0.5 × (2/4) = 0.25 moles of Al₂O₃.

31. How many grams of potassium (K) are needed to react with 1 mole of Cl₂ to produce potassium chloride (KCl)? (Molar mass of K = 39 g/mol)

A) 39 g
B) 78 g
C) 117 g
D) 156 g

Answer: A) 39 g

Explanation: The reaction is 2K + Cl₂ → 2KCl, indicating that 1 mole of Cl₂ requires 1 mole of K. Thus, 39 g of K is needed.

32. If 10 g of NaCl is dissolved in water, how many moles of NaCl are present? (Molar mass of NaCl = 58.5 g/mol)

A) 0.17 moles
B) 0.25 moles
C) 0.5 moles
D) 1 mole

Answer: A) 0.17 moles

Explanation: Moles = mass / molar mass = 10 g / 58.5 g/mol = 0.171 moles.

33. In the reaction 2H₂ + O₂ → 2H₂O, what is the mole ratio of H₂ to H₂O?

A) 1:1
B) 2:1
C) 1:2
D) 3:2

Answer: B) 2:1

Explanation: The balanced equation indicates that 2 moles of H₂ produce 2 moles of H₂O, giving a ratio of 2:2, which simplifies to 1:1.

34. If 5 moles of CH₄ are burned in oxygen, how many moles of CO₂ are produced? (CH₄ + 2O₂ → CO₂ + 2H₂O)

A) 5 moles
B) 10 moles
C) 2.5 moles
D) 7.5 moles

Answer: A) 5 moles

Explanation: The reaction shows that 1 mole of CH₄ produces 1 mole of CO₂, so 5 moles of CH₄ yield 5 moles of CO₂.

35. What is the mass of 2 moles of ethylene glycol (C₂H₆O₂)? (Molar mass of C₂H₆O₂ = 62 g/mol)

A) 62 g
B) 124 g
C) 186 g
D) 248 g

Answer: B) 124 g

Explanation: Mass = moles × molar mass = 2 moles × 62 g/mol = 124 g.

36. How many moles of O₂ are needed to react with 4 moles of NH₃ in the reaction: 4NH₃ + 5O₂ → 4NO + 6H₂O?

A) 4 moles
B) 5 moles
C) 6 moles
D) 10 moles

Answer: B) 5 moles

Explanation: According to the balanced equation, 4 moles of NH₃ react with 5 moles of O₂.

37. In the reaction 2K + Cl₂ → 2KCl, how many grams of chlorine are needed to react with 3 moles of K? (Molar mass of Cl₂ = 71 g/mol)

A) 71 g
B) 106 g
C) 142 g
D) 213 g

Answer: B) 106 g

Explanation: The balanced equation shows that 2 moles of K require 1 mole of Cl₂. Therefore, 3 moles of K require 3 × (1/2) = 1.5 moles of Cl₂, which equals 1.5 × 71 g/mol = 106.5 g.

38. What is the mass of 4 moles of sulfur (S)? (Molar mass of S = 32 g/mol)

A) 64 g
B) 128 g
C) 96 g
D) 112 g

Answer: C) 128 g

Explanation: Mass = moles × molar mass = 4 moles × 32 g/mol = 128 g.

39. If 8 moles of Ca(OH)₂ are used in a reaction, how many moles of water are produced? (Ca(OH)₂ + CO₂ → CaCO₃ + H₂O)

A) 2 moles
B) 4 moles
C) 8 moles
D) 16 moles

Answer: C) 8 moles

Explanation: The balanced equation shows that 1 mole of Ca(OH)₂ produces 1 mole of H₂O, so 8 moles of Ca(OH)₂ yield 8 moles of H₂O.

40. In the reaction 2C₆H₁₂ + 17O₂ → 12CO₂ + 12H₂O, how many grams of CO₂ are produced from 2 moles of C₆H₁₂? (Molar mass of CO₂ = 44 g/mol)

A) 528 g
B) 352 g
C) 264 g
D) 220 g

Answer: A) 528 g

Explanation: 2 moles of C₆H₁₂ produce 12 moles of CO₂. Mass = 12 moles × 44 g/mol = 528 g.

41. How many grams of glucose (C₆H₁₂O₆) are needed to produce 4 moles of ethanol (C₂H₅OH)? (C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂)

A) 90 g
B) 180 g
C) 360 g
D) 720 g

Answer: C) 720 g

Explanation: From the reaction, 1 mole of glucose produces 2 moles of ethanol. Thus, 4 moles of ethanol require 2 moles of glucose. Mass = 2 moles × 180 g/mol = 360 g.

42. What is the percentage composition of hydrogen in water (H₂O)?

A) 33%
B) 11%
C) 22%
D) 67%

Answer: A) 11%

Explanation: The molar mass of H₂O is 18 g/mol. The mass of H is 2 g, so the percentage is (2/18) × 100 = 11.11%.

43. If 0.5 moles of H₂ react with excess O₂, how many moles of water (H₂O) will be produced? (2H₂ + O₂ → 2H₂O)

A) 0.5 moles
B) 1 mole
C) 2 moles
D) 3 moles

Answer: B) 0.5 moles

Explanation: From the balanced equation, 2 moles of H₂ produce 2 moles of H₂O, so 0.5 moles of H₂ will produce 0.5 moles of H₂O.

44. What is the molar mass of potassium nitrate (KNO₃)?

A) 85 g/mol
B) 120 g/mol
C) 146 g/mol
D) 196 g/mol

Answer: C) 101 g/mol

Explanation: Molar mass = (39) + (14) + (3 × 16) = 39 + 14 + 48 = 101 g/mol.

45. In the reaction 2Na + Cl₂ → 2NaCl, how many moles of NaCl are formed from 3 moles of Na?

A) 1.5 moles
B) 2 moles
C) 3 moles
D) 4.5 moles

Answer: B) 3 moles

Explanation: The reaction shows that 2 moles of Na produce 2 moles of NaCl, so 3 moles of Na produce 3 moles of NaCl.

46. How many grams of oxygen are needed to react with 2 moles of hydrogen? (2H₂ + O₂ → 2H₂O; Molar mass of O₂ = 32 g/mol)

A) 16 g
B) 32 g
C) 48 g
D) 64 g

Answer: B) 32 g

Explanation: The balanced equation indicates that 2 moles of H₂ react with 1 mole of O₂, so for 2 moles of H₂, you need 1 mole of O₂, which equals 32 g.

47. If 10 g of NaCl is dissolved in water, how many moles of NaCl are present? (Molar mass of NaCl = 58.5 g/mol)

A) 0.17 moles
B) 0.25 moles
C) 0.5 moles
D) 1 mole

Answer: B) 0.17 moles

Explanation: Moles = mass / molar mass = 10 g / 58.5 g/mol ≈ 0.171 moles.

48. What is the volume of 4 moles of gas at STP? (1 mole = 22.4 L)

A) 44.8 L
B) 67.2 L
C) 89.6 L
D) 100 L

Answer: C) 89.6 L

Explanation: Volume = moles × volume per mole = 4 moles × 22.4 L/mole = 89.6 L.

49. How many grams of Na₂SO₄ can be produced from the reaction of 2 moles of Na with excess sulfuric acid? (2Na + H₂SO₄ → Na₂SO₄ + H₂)

A) 74 g
B) 142 g
C) 196 g
D) 252 g

Answer: B) 142 g

Explanation: The balanced equation shows that 2 moles of Na produce 1 mole of Na₂SO₄. The molar mass of Na₂SO₄ is 142 g/mol, so mass = 1 × 142 g = 142 g.

50. If 4 moles of CO₂ are produced, how many moles of glucose are needed? (C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O)

A) 1 mole
B) 2 moles
C) 3 moles
D) 4 moles

Answer: B) 2 moles

Explanation: 1 mole of glucose produces 6 moles of CO₂, so to produce 4 moles of CO₂, you need (4/6) = 0.67 moles of glucose.

51. In the reaction 3H₂ + N₂ → 2NH₃, how many moles of NH₃ are produced from 3 moles of H₂?

A) 1.5 moles
B) 2 moles
C) 3 moles
D) 4 moles

Answer: A) 3 moles

Explanation: The reaction shows that 3 moles of H₂ produce 2 moles of NH₃, so 3 moles of H₂ will yield 2 moles of NH₃.

52. How many grams of KCl are in 3 moles? (Molar mass of KCl = 74.5 g/mol)

A) 149 g
B) 224 g
C) 300 g
D) 448.5 g

Answer: A) 224 g

Explanation: Mass = moles × molar mass = 3 moles × 74.5 g/mol = 223.5 g.

53. In the reaction 2Na + 2H₂O → 2NaOH + H₂, how many moles of NaOH are produced from 5 moles of Na?

A) 2.5 moles
B) 5 moles
C) 10 moles
D) 15 moles

Answer: B) 5 moles

Explanation: The balanced equation indicates that 2 moles of Na produce 2 moles of NaOH, so 5 moles of Na will produce 5 moles of NaOH.

54. If 1 mole of glucose (C₆H₁₂O₆) is fermented, how many moles of carbon dioxide are produced? (C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂)

A) 1 mole
B) 2 moles
C) 3 moles
D) 4 moles

Answer: B) 2 moles

Explanation: The fermentation process shows that 1 mole of glucose produces 2 moles of CO₂.

55. How many moles of CO are produced from the complete combustion of 2 moles of methanol (CH₃OH)? (2CH₃OH + 3O₂ → 2CO₂ + 4H₂O)

A) 2 moles
B) 4 moles
C) 6 moles
D) 8 moles

Answer: A) 2 moles

Explanation: The reaction shows that 2 moles of methanol produce 2 moles of CO.

56. What is the mass of 0.25 moles of CaCO₃? (Molar mass of CaCO₃ = 100 g/mol)

A) 25 g
B) 50 g
C) 75 g
D) 100 g

Answer: B) 25 g

Explanation: Mass = moles × molar mass = 0.25 moles × 100 g/mol = 25 g.

57. In the reaction 2K + Cl₂ → 2KCl, how many moles of Cl₂ are needed to react with 4 moles of K?

A) 1 mole
B) 2 moles
C) 3 moles
D) 4 moles

Answer: B) 2 moles

Explanation: The balanced equation shows that 2 moles of K react with 1 mole of Cl₂, so 4 moles of K will require 2 moles of Cl₂.

58. How many grams of NH₃ can be produced from 3 moles of N₂? (N₂ + 3H₂ → 2NH₃; Molar mass of NH₃ = 17 g/mol)

A) 51 g
B) 102 g
C) 153 g
D) 204 g

Answer: B) 102 g

Explanation: 3 moles of N₂ produce 6 moles of NH₃, so mass = 6 moles × 17 g/mol = 102 g.

59. How many liters of CO₂ are produced from 2 moles of C₆H₁₂O₆? (C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O; at STP 1 mole = 22.4 L)

A) 44.8 L
B) 134.4 L
C) 268.8 L
D) 400 L

Answer: C) 268.8 L

Explanation: 2 moles of glucose produce 12 moles of CO₂, so volume = 12 × 22.4 L = 268.8 L.

60. What is the molar mass of aluminum sulfate (Al₂(SO₄)₃)?

A) 150 g/mol
B) 200 g/mol
C) 250 g/mol
D) 300 g/mol

Answer: C) 342 g/mol

Explanation: Molar mass = (2×27) + (3×32) + (12×16) = 54 + 96 + 192 = 342 g/mol

61. How many grams of aluminum (Al) are needed to produce 4 moles of aluminum oxide (Al₂O₃)? (Molar mass of Al = 27 g/mol)

A) 54 g
B) 108 g
C) 216 g
D) 324 g

Answer: B) 216 g

Explanation: The reaction is 4Al + 3O₂ → 2Al₂O₃. To produce 4 moles of Al₂O₃, you need 8 moles of Al. Mass = 8 moles × 27 g/mol = 216 g.

62. In the reaction 2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O, how many moles of CO₂ are produced from 2 moles of C₄H₁₀?

A) 4 moles
B) 8 moles
C) 10 moles
D) 12 moles

Answer: B) 8 moles

Explanation: The reaction indicates that 2 moles of C₄H₁₀ produce 8 moles of CO₂.

63. If 10 g of NaOH is dissolved in water, how many moles of NaOH are present? (Molar mass of NaOH = 40 g/mol)

A) 0.25 moles
B) 0.5 moles
C) 0.75 moles
D) 1 mole

Answer: B) 0.25 moles

Explanation: Moles = mass / molar mass = 10 g / 40 g/mol = 0.25 moles.

64. How many moles of H₂ are produced when 2 moles of Mg react with 2 moles of HCl? (Mg + 2HCl → MgCl₂ + H₂)

A) 1 mole
B) 2 moles
C) 3 moles
D) 4 moles

Answer: B) 2 moles

Explanation: The balanced equation indicates that 1 mole of Mg produces 1 mole of H₂, so 2 moles of Mg produce 2 moles of H₂.

65. What is the molar mass of sodium sulfate (Na₂SO₄)?

A) 126 g/mol
B) 142 g/mol
C) 150 g/mol
D) 178 g/mol

Answer: A) 142 g/mol

Explanation: Molar mass = (2×23) + (32) + (4×16) = 46 + 32 + 64 = 142 g/mol.

66. If 5 moles of CO₂ are produced, how many moles of glucose are needed? (C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O)

A) 2.5 moles
B) 5 moles
C) 7.5 moles
D) 10 moles

Answer: B) 5 moles

Explanation: The balanced equation indicates that 1 mole of glucose produces 6 moles of CO₂, so to produce 5 moles of CO₂, you need (5/6) moles of glucose, which is approximately 0.83 moles.

67. In the reaction 2K + Cl₂ → 2KCl, how many grams of KCl are produced from 4 moles of K? (Molar mass of KCl = 74.5 g/mol)

A) 149 g
B) 298 g
C) 372 g
D) 448 g

Answer: B) 298 g

Explanation: 4 moles of K produce 4 moles of KCl. Mass = 4 moles × 74.5 g/mol = 298 g.

68. What is the volume of 3 moles of gas at STP? (1 mole = 22.4 L)

A) 22.4 L
B) 44.8 L
C) 67.2 L
D) 72.8 L

Answer: C) 67.2 L

Explanation: Volume = moles × volume per mole = 3 moles × 22.4 L/mole = 67.2 L.

69. How many grams of K₂SO₄ can be produced from the reaction of 2 moles of K with excess sulfuric acid? (K + H₂SO₄ → K₂SO₄ + H₂)

A) 94 g
B) 196 g
C) 228 g
D) 312 g

Answer: B) 196 g

Explanation: The balanced equation shows that 2 moles of K produce 1 mole of K₂SO₄. The molar mass of K₂SO₄ is 174 g/mol, so mass = 1 × 174 g = 174 g.

70. If 0.5 moles of Ca(OH)₂ are used, how many moles of water are produced? (Ca(OH)₂ + CO₂ → CaCO₃ + H₂O)

A) 0.5 moles
B) 1 mole
C) 2 moles
D) 3 moles

Answer: A) 0.5 moles

Explanation: The balanced equation shows that 1 mole of Ca(OH)₂ produces 1 mole of H₂O, so 0.5 moles of Ca(OH)₂ will yield 0.5 moles of H₂O.

71. How many moles of NH₄Cl are present in 58.5 g? (Molar mass of NH₄Cl = 53.5 g/mol)

A) 1 mole
B) 2 moles
C) 3 moles
D) 4 moles

Answer: A) 1 mole

Explanation: Moles = mass / molar mass = 58.5 g / 53.5 g/mol = 1.09 moles.

72. What is the mass of 2 moles of sodium bicarbonate (NaHCO₃)? (Molar mass of NaHCO₃ = 84 g/mol)

A) 168 g
B) 120 g
C) 96 g
D) 80 g

Answer: A) 168 g

Explanation: Mass = moles × molar mass = 2 moles × 84 g/mol = 168 g.

73. How many moles of H₂O can be produced from the complete combustion of 3 moles of C₃H₈? (C₃H₈ + 5O₂ → 3CO₂ + 4H₂O)

A) 6 moles
B) 8 moles
C) 12 moles
D) 15 moles

Answer: B) 12 moles

Explanation: The reaction shows that 1 mole of C₃H₈ produces 4 moles of H₂O, so 3 moles of C₃H₈ will produce 3 × 4 = 12 moles of H₂O.

74. If you have 10 g of CaCO₃, how many moles do you have? (Molar mass of CaCO₃ = 100 g/mol)

A) 0.1 moles
B) 0.5 moles
C) 1 mole
D) 2 moles

Answer: C) 0.1 moles

Explanation: Moles = mass / molar mass = 10 g / 100 g/mol = 0.1 moles.

75. In the reaction 2Na + Cl₂ → 2NaCl, what is the mass of sodium chloride produced from 3 moles of Na? (Molar mass of NaCl = 58.5 g/mol)

A) 87.75 g
B) 174 g
C) 117 g
D) 75 g

Answer: B) 174 g

Explanation: 3 moles of Na produce 3 moles of NaCl, so mass = 3 × 58.5 g/mol = 175.5 g.

76. What is the total number of moles in a solution containing 2 moles of NaCl and 3 moles of KCl?

A) 2 moles
B) 3 moles
C) 5 moles
D) 6 moles

Answer: D) 5 moles

Explanation: The total number of moles = 2 moles (NaCl) + 3 moles (KCl) = 5 moles.

77. How many liters of oxygen gas are needed to completely react with 4 moles of propane (C₃H₈)? (C₃H₈ + 5O₂ → 3CO₂ + 4H₂O)

A) 44.8 L
B) 56.8 L
C) 67.2 L
D) 88.4 L

Answer: D) 88.4 L

Explanation: 1 mole of C₃H₈ reacts with 5 moles of O₂, so 4 moles of C₃H₈ will require 4 × 5 = 20 moles of O₂. At STP, volume = 20 × 22.4 L = 448 L.

78. How many grams of Fe₂O₃ are produced from 4 moles of Fe? (4Fe + 3O₂ → 2Fe₂O₃; Molar mass of Fe₂O₃ = 160 g/mol)

A) 80 g
B) 160 g
C) 240 g
D) 320 g

Answer: C) 240 g

Explanation: 4 moles of Fe will produce 2 moles of Fe₂O₃. Thus, mass = 2 × 160 g/mol = 320 g.

79. If you have 100 g of glucose (C₆H₁₂O₆), how many moles do you have? (Molar mass of glucose = 180 g/mol)

A) 0.5 moles
B) 1 mole
C) 2 moles
D) 3 moles

Answer: A) 0.55 moles

Explanation: Moles = mass / molar mass = 100 g / 180 g/mol = 0.56 moles.

80. In the reaction 2H₂ + O₂ → 2H₂O, how many grams of water are produced from 4 moles of H₂? (Molar mass of H₂O = 18 g/mol)

A) 72 g
B) 36 g
C) 54 g
D) 18 g

Answer: A) 72 g

Explanation: 4 moles of H₂ produce 4 moles of H₂O, so mass = 4 × 18 g/mol = 72 g.

81. How many moles of KCl are produced when 2 moles of K react with Cl₂? (2K + Cl₂ → 2KCl)

A) 1 mole
B) 2 moles
C) 3 moles
D) 4 moles

Answer: B) 2 moles

Explanation: The balanced equation indicates that 2 moles of K produce 2 moles of KCl, so 2 moles of K will yield 2 moles of KCl.

82. If 8 moles of H₂ react completely, how many moles of O₂ are needed? (2H₂ + O₂ → 2H₂O)

A) 1 mole
B) 2 moles
C) 3 moles
D) 4 moles

Answer: B) 2 moles

Explanation: The balanced equation shows that 2 moles of H₂ require 1 mole of O₂. Therefore, 8 moles of H₂ will need 4 moles of O₂.

83. In the reaction 3Fe + 2O₂ → Fe₃O₄, how many grams of Fe₃O₄ can be produced from 6 moles of Fe? (Molar mass of Fe₃O₄ = 232 g/mol)

A) 116 g
B) 232 g
C) 464 g
D) 696 g

Answer: C) 464 g

Explanation: 6 moles of Fe produce 2 moles of Fe₃O₄. Thus, mass = 2 × 232 g/mol = 464 g.

84. How many grams of water are produced from the complete combustion of 2 moles of ethane (C₂H₆)? (C₂H₆ + 7/2 O₂ → 2CO₂ + 3H₂O; Molar mass of H₂O = 18 g/mol)

A) 36 g
B) 54 g
C) 72 g
D) 90 g

Answer: B) 54 g

Explanation: 2 moles of C₂H₆ produce 6 moles of H₂O. Thus, mass = 6 × 18 g/mol = 108 g.

85. If you have 1 mole of NaCl, how many grams do you have? (Molar mass of NaCl = 58.5 g/mol)

A) 58.5 g
B) 100 g
C) 150 g
D) 200 g

Answer: A) 58.5 g

Explanation: Mass = moles × molar mass = 1 mole × 58.5 g/mol = 58.5 g.

86. In the reaction 2C₂H₄ + 5O₂ → 4CO₂ + 4H₂O, how many moles of CO₂ are produced from 1 mole of C₂H₄?

A) 1 mole
B) 2 moles
C) 3 moles
D) 4 moles

Answer: B) 2 moles

Explanation: The balanced equation indicates that 2 moles of C₂H₄ produce 4 moles of CO₂, so 1 mole of C₂H₄ produces 2 moles of CO₂.

87. What is the molar mass of magnesium sulfate (MgSO₄)?

A) 120 g/mol
B) 146 g/mol
C) 150 g/mol
D) 178 g/mol

Answer: B) 120 g/mol

Explanation: Molar mass = (24.3) + (32) + (4 × 16) = 24.3 + 32 + 64 = 120.3 g/mol.

88. If 1 mole of glucose (C₆H₁₂O₆) is fermented, how many moles of ethanol (C₂H₅OH) are produced? (C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂)

A) 1 mole
B) 2 moles
C) 3 moles
D) 4 moles

Answer: B) 2 moles

Explanation: The reaction shows that 1 mole of glucose produces 2 moles of ethanol.

89. How many grams of CO₂ are produced from the combustion of 2 moles of octane (C₈H₁₈)? (2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O; Molar mass of CO₂ = 44 g/mol)

A) 88 g
B) 176 g
C) 352 g
D) 704 g

Answer: C) 704 g

Explanation: 2 moles of octane produce 16 moles of CO₂. Thus, mass = 16 × 44 g/mol = 704 g.

90. What is the total number of moles in a solution containing 5 moles of NaCl and 4 moles of KBr?

A) 7 moles
B) 9 moles
C) 10 moles
D) 11 moles

Answer: B) 9 moles

Explanation: Total moles = 5 moles (NaCl) + 4 moles (KBr) = 9 moles.

91. In the reaction 2Na + 2H₂O → 2NaOH + H₂, how many moles of hydrogen gas are produced from 3 moles of Na?

A) 1.5 moles
B) 2 moles
C) 3 moles
D) 4.5 moles

Answer: A) 1.5 moles

Explanation: The balanced equation shows that 2 moles of Na produce 1 mole of H₂, so 3 moles of Na produce (3/2) moles of H₂ = 1.5 moles.

92. How many grams of H₂O are produced from the combustion of 1 mole of methane (CH₄)? (CH₄ + 2O₂ → CO₂ + 2H₂O; Molar mass of H₂O = 18 g/mol)

A) 18 g
B) 36 g
C) 54 g
D) 72 g

Answer: A) 36 g

Explanation: 1 mole of CH₄ produces 2 moles of H₂O, so mass = 2 × 18 g/mol = 36 g.

93. How many moles of H₂ are in 22 g of H₂ gas? (Molar mass of H₂ = 2 g/mol)

A) 5 moles
B) 10 moles
C) 15 moles
D) 20 moles

Answer: B) 11 moles

Explanation: Moles = mass / molar mass = 22 g / 2 g/mol = 11 moles.

94. What is the molar mass of ammonium phosphate ((NH₄)₃PO₄)?

A) 132 g/mol
B) 149 g/mol
C) 194 g/mol
D) 250 g/mol

Answer: C) 149 g/mol

Explanation: Molar mass = (3×14) + (12×1) + (31) + (4×16) = 42 + 12 + 31 + 64 = 149 g/mol.

95. If you have 50 g of NaCl, how many moles do you have? (Molar mass of NaCl = 58.5 g/mol)

A) 0.85 moles
B) 1 mole
C) 1.5 moles
D) 2 moles

Answer: A) 0.85 moles

Explanation: Moles = mass / molar mass = 50 g / 58.5 g/mol ≈ 0.85 moles.

96. In the reaction 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O, how many moles of water are produced from 3 moles of C₂H₆?

A) 6 moles
B) 9 moles
C) 12 moles
D) 18 moles

Answer: B) 9 moles

Explanation: The reaction indicates that 2 moles of C₂H₆ produce 6 moles of H₂O, so 3 moles of C₂H₆ will produce (3/2) × 6 = 9 moles.

97. How many grams of glucose are in 0.5 moles? (Molar mass of glucose = 180 g/mol)

A) 45 g
B) 90 g
C) 180 g
D) 360 g

Answer: B) 90 g

Explanation: Mass = moles × molar mass = 0.5 moles × 180 g/mol = 90 g.

98. In the reaction 3Fe + 2O₂ → Fe₃O₄, how many moles of Fe₃O₄ can be produced from 6 moles of Fe?

A) 2 moles
B) 3 moles
C) 4 moles
D) 5 moles

Answer: A) 2 moles

Explanation: The balanced equation shows that 3 moles of Fe produce 1 mole of Fe₃O₄, so 6 moles of Fe will produce 2 moles of Fe₃O₄.

99. How many liters of carbon dioxide gas are produced when 2 moles of glucose are completely oxidized? (C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O; at STP 1 mole = 22.4 L)

A) 22.4 L
B) 44.8 L
C) 134.4 L
D) 268.8 L

Answer: C) 134.4 L

Explanation: 2 moles of glucose produce 12 moles of CO₂. Thus, volume = 12 moles × 22.4 L/mole = 268.8 L.

100. How many moles of NaOH can be formed from the reaction of 2 moles of Na with 2 moles of water? (2Na + 2H₂O → 2NaOH + H₂)

A) 1 mole
B) 2 moles
C) 3 moles
D) 4 moles

Answer: B) 2 moles

Explanation: The balanced equation shows that 2 moles of Na react to produce 2 moles of NaOH.