9th class Chemistry, Chapter 4: Stoichiometry MCQs

1. How many atoms are present in one gram of H₂O?

1. (A) 1.002 × 10²³ atoms ✓
2. (B) 6.022 × 10²³ atoms
3. (C) 0.334 × 10²³ atoms
4. (D) 2.004 × 10²³ atoms

2. Which is the correct formula of calcium phosphide?

1. (A) CaP
2. (B) CaP₂
3. (C) Ca₂P₃
4. (D) Ca₃P₂ ✓

3. How many atomic mass units (amu) are there in one gram?

1. (A) 1 amu
2. (B) 10²³ amu
3. (C) 6.022 × 10²³ amu ✓
4. (D) 6.022 × 10²² amu

4. Structural formula of 2-hexene is CH₃−CH=CH−(CH₂)₂−CH₃. What will be its empirical formula?

1. (A) C₂H₂
2. (B) CH
3. (C) C₆H₁₂
4. (D) CH₂ ✓

5. How many moles are there in 25 g of H₂SO₄?

1. (A) 0.765 moles
2. (B) 0.51 moles
3. (C) 0.255 moles ✓
4. (D) 0.4 moles

6. A necklace has 6 g of diamonds in it. What are the number of carbon atoms in it?

1. (A) 6.02 × 10²³
2. (B) 12.04 × 10²³
3. (C) 1.003 × 10²³
4. (D) 3.01 × 10²³ ✓

7. What is the mass of Al in 204 g of aluminium oxide, Al₂O₃?

1. (A) 26 g
2. (B) 27 g
3. (C) 54 g
4. (D) 108 g ✓

8. Which one of the following compounds will have the highest percentage of the mass of nitrogen?

1. (A) CO(NH₂)₂
2. (B) N₂H₄ ✓
3. (C) NH₃
4. (D) NH₂OH

9. When one mole of each of the following compounds is reacted with oxygen, which will produce the maximum amount of CO₂?

1. (A) Carbon
2. (B) Diamond
3. (C) Ethane (C₂H₆) ✓
4. (D) Methane (CH₄)

10. What mass of 95% CaCO₃ will be required to neutralize 50 cm³ of 0.5M HCl solution?

1. (A) 9.5 g
2. (B) 1.25 g
3. (C) 1.32 g ✓
4. (D) 1.45 g

11. Stoichiometry helps us to calculate the amounts of reactants and products by using a:

1. (A) Structural formula
2. (B) Periodic table
3. (C) Crystal lattice
4. (D) Balanced chemical equation ✓

12. Stoichiometry is based on the law of:

1. (A) Octet
2. (B) Radioactive decay
3. (C) Conservation of mass ✓
4. (D) Definite proportions only

13. The chemical formula of ozone is:

1. (A) O₂
2. (B) O
3. (C) O₄
4. (D) O₃ ✓

14. Sodium chloride is represented by a formula unit NaCl because the ratio of its ions is:

1. (A) 1 : 1 ✓
2. (B) 1 : 2
3. (C) 2 : 1
4. (D) 1 : 3

15. The formula that shows all the types and numbers of atoms bonded together in one molecule is the:

1. (A) Empirical formula
2. (B) Formula unit
3. (C) Structural formula only
4. (D) Molecular formula ✓

16. Which of the following elements exists as discrete molecules?

1. (A) N₂ ✓
2. (B) Na
3. (C) Fe
4. (D) C

17. The simplest whole number ratio of atoms in a compound is shown by its:

1. (A) Molar mass
2. (B) Empirical formula ✓
3. (C) Molecular formula
4. (D) Structural formula

18. The empirical formula of hydrogen peroxide (H₂O₂) is:

1. (A) OH₂
2. (B) HO ✓
3. (C) H₂O
4. (D) H₂O₂

19. The empirical formula of benzene (C₆H₆) is:

1. (A) C₆H₆
2. (B) CH ✓
3. (C) C₂H₂
4. (D) CH₂

20. Benzene and acetylene have the same:

1. (A) Number of atoms
2. (B) Empirical formula ✓
3. (C) Molecular formula
4. (D) Molar mass