CHAPTER 1
Some Basic Concepts of Chemistry
1. Which law states that a chemical reaction can neither create nor destroy mass?
a) Law of Definite Proportions
b) Law of Conservation of Mass✔️
c) Law of Multiple Proportions
d) Avogadro’s Law
2. Who gave the Law of Multiple Proportions?
a) John Dalton✔️
b) Joseph Proust
c) Antoine Lavoisier
d) Robert Boyle
3. Which law states that a chemical compound always contains the same elements in the same proportion by mass?
a) Law of Definite Proportions✔️
b) Law of Conservation of Mass
c) Law of Multiple Proportions
d) Dalton’s Law
4. Dalton’s atomic theory explains:
a) Nuclear reactions
b) Law of Definite Proportions✔️
c) Radioactivity
d) Behavior of gases
5. The molecular mass of oxygen (O₂) is:
a) 16 amu
b) 32 amu✔️
c) 18 amu
d) 44 amu
6. How many molecules are present in 1 mole of a substance?
a) 3.011 × 10²³
b) 6.022 × 10²³✔️
c) 1.602 × 10⁻¹⁹
d) 9.8 × 10⁸
7. The molar mass of water (H₂O) is:
a) 16 g/mol
b) 18 g/mol✔️
c) 32 g/mol
d) 44 g/mol
8. What is the empirical formula of glucose (C₆H₁₂O₆)?
a) CH₂O✔️
b) C₂H₄O₂
c) C₆H₆
d) CH₄
9. In which compound is the mass ratio of hydrogen to oxygen 1:8?
a) H₂O✔️
b) H₂O₂
c) CO₂
d) NaOH
10. What is the percentage of carbon in methane (CH₄)? (C = 12, H = 1)
a) 75%✔️
b) 50%
c) 25%
d) 12.5%
11. What is the mass of 1 mole of nitrogen gas (N₂)?
a) 14 g
b) 28 g✔️
c) 32 g
d) 44 g
12. How many grams are present in 0.5 moles of CO₂? (Molar mass of CO₂ = 44 g/mol)
a) 11 g
b) 22 g✔️
c) 44 g
d) 88 g
13. The ratio of atoms in the empirical formula of a compound with molecular formula C₂H₄ is:
a) 1:1
b) 1:2✔️
c) 2:1
d) 3:1
14. Which gas has a molar mass of 2 g/mol?
a) Helium
b) Hydrogen✔️
c) Oxygen
d) Nitrogen
15. How many atoms are in 0.5 moles of oxygen gas (O₂)?
a) 3.011 × 10²³✔️
b) 6.022 × 10²³
c) 1.204 × 10²⁴
d) 9.033 × 10²³
16. Which of the following compounds has the highest percentage of oxygen?
a) H₂O✔️
b) CO₂
c) CH₄
d) NH₃
17. What is the percentage composition of hydrogen in water? (H₂O)
a) 11.1%✔️
b) 18.0%
c) 8.0%
d) 50%
18. What is the molecular formula of a compound with empirical formula CH₂ and molar mass 42 g/mol?
a) C₂H₄
b) C₃H₆✔️
c) C₄H₈
d) CH₄
19. How many moles of hydrogen are present in 1 mole of H₂O?
a) 1
b) 2✔️
c) 0.5
d) 3
20. What is the stoichiometric coefficient of oxygen in the equation: 2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O?
a) 8
b) 10
c) 13✔️
d) 2
21. How many moles of water are formed when 2 moles of H₂ react with 1 mole of O₂?
a) 1
b) 2
c) 3
d) 2✔️
22. Which reagent is limiting when 5 moles of H₂ react with 2 moles of O₂?
a) H₂
b) O₂✔️
c) H₂O
d) None
23. How many grams of NaOH are required to prepare 1 M solution in 500 mL of water? (Molar mass of NaOH = 40 g/mol)
a) 10 g✔️
b) 20 g
c) 30 g
d) 40 g
24. What is the molecular mass of NaCl?
a) 58.5 amu✔️
b) 60 amu
c) 65.5 amu
d) 50 amu
25. What is the ratio of nitrogen to hydrogen in ammonia (NH₃) by mass?
a) 14:1
b) 1:3
c) 14:3✔️
d) 1:2
26. Which gas has the lowest molar mass?
a) Hydrogen✔️
b) Oxygen
c) Nitrogen
d) Helium
27. How many moles of oxygen molecules are present in 64 g of O₂? (O = 16)
a) 1
b) 2✔️
c) 3
d) 4
28. What is the empirical formula of benzene (C₆H₆)?
a) CH✔️
b) CH₂
c) C₂H₂
d) C₃H₆
29. What is the molar mass of sulfuric acid (H₂SO₄)?
a) 98 g/mol✔️
b) 100 g/mol
c) 90 g/mol
d) 88 g/mol
30. Which compound contains 40% carbon, 6.7% hydrogen, and 53.3% oxygen?
a) Glucose
b) Methane
c) Ethanol
d) CH₂O✔️
31. What is the percentage of nitrogen in NH₃? (N = 14, H = 1)
a) 82.4%✔️
b) 17.6%
c) 50%
d) 14%
32. How many moles are in 100 g of NaOH? (Na = 23, O = 16, H = 1)
a) 2.5✔️
b) 4
c) 1
d) 3
33. What is the molecular mass of methane (CH₄)?
a) 16 amu✔️
b) 18 amu
c) 32 amu
d) 44 amu
34. Which element has the highest percentage composition in H₂SO₄?
a) Hydrogen
b) Sulfur
c) Oxygen✔️
d) Carbon
35. How many atoms are present in 1 mole of H₂ gas?
a) 6.022 × 10²³
b) 1.204 × 10²⁴✔️
c) 3.011 × 10²³
d) 9.033 × 10²³
36. What is the mass of 0.25 mole of CO₂?
a) 22 g
b) 11 g✔️
c) 44 g
d) 88 g
37. The volume occupied by 1 mole of any gas at STP is:
a) 22.4 L✔️
b) 24 L
c) 18 L
d) 10 L
38. Which of the following is an example of a combination reaction?
a) 2H₂ + O₂ → 2H₂O✔️
b) CaCO₃ → CaO + CO₂
c) Zn + HCl → ZnCl₂ + H₂
d) NaCl → Na⁺ + Cl⁻
39. What mass of oxygen is required to react with 4 g of hydrogen to form water?
a) 32 g✔️
b) 8 g
c) 4 g
d) 16 g
40. What is the limiting reagent when 10 g of H₂ reacts with 20 g of O₂? (H = 1, O = 16)
a) H₂✔️
b) O₂
c) H₂O
d) Both are limiting
41. What is the molecular formula of a compound with empirical formula NO₂ and molar mass 92 g/mol?
a) NO
b) N₂O₂
c) NO₂
d) N₂O₄✔️
42. What is the volume of 1 mole of oxygen gas at STP?
a) 22.4 L✔️
b) 11.2 L
c) 44.8 L
d) 18 L
43. How many grams are in 0.1 moles of H₂SO₄?
a) 9.8 g...