FSc Part 1 Chemistry chapter 1: Basic concepts MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

30 exam-style questions on Basic concepts, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

30 questions · 3 topics · 10 per test

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What chapter 1 covers

Ten Basic concepts questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. 5.4 g of aluminium is heated with 14.2 g of chlorine. What mass of AlCl3 can form? 2Al + 3Cl2 → 2AlCl3 (AlCl3 = 133.5)

  1. A
    26.7 g
  2. B
    17.8 g
  3. C
    19.6 g
  4. D
    13.35 g
Show answer

Answer: B. Al = 0.2 mol needs 0.3 mol Cl2, but only 0.2 mol Cl2 is present, so Cl2 limits: 0.2 × 2/3 = 0.1333 mol AlCl3 × 133.5 = 17.8 g. 26.7 g assumes Al is limiting.

2. Which element has the largest number of naturally occurring stable isotopes?

  1. A
    carbon
  2. B
    tin
  3. C
    fluorine
  4. D
    chlorine
Show answer

Answer: B. Tin has ten stable isotopes, the most of any element. Fluorine has only one, and carbon and chlorine have two each.

3. 6.5 g of zinc (Zn = 65) reacts with excess dilute HCl. What volume of hydrogen is produced at STP? Zn + 2HCl → ZnCl2 + H2

  1. A
    2.24 dm3
  2. B
    1.12 dm3
  3. C
    4.48 dm3
  4. D
    22.4 dm3
Show answer

Answer: A. 6.5 ÷ 65 = 0.1 mol Zn gives 0.1 mol H2; 0.1 × 22.4 = 2.24 dm3. The 2 in front of HCl does not change the Zn : H2 ratio of 1 : 1.

4. What mass of carbon dioxide is produced when 8 g of methane burns completely? CH4 + 2O2 → CO2 + 2H2O

  1. A
    11 g
  2. B
    22 g
  3. C
    44 g
  4. D
    16 g
Show answer

Answer: B. 8 ÷ 16 = 0.5 mol CH4 gives 0.5 mol CO2 = 0.5 × 44 = 22 g.

5. 10 g of calcium carbonate is heated strongly and 3.3 g of carbon dioxide is collected. What is the percentage yield? CaCO3 → CaO + CO2

  1. A
    33%
  2. B
    44%
  3. C
    75%
  4. D
    133%
Show answer

Answer: C. 0.1 mol CaCO3 should give 0.1 mol CO2 = 4.4 g. Yield = 3.3 ÷ 4.4 × 100 = 75%.

6. 0.64 g of a gas occupies 224 cm3 at STP. Which gas could it be?

  1. A
    O2
  2. B
    CO2
  3. C
    SO3
  4. D
    SO2
Show answer

Answer: D. 224 cm3 ÷ 22 414 cm3 = 0.0100 mol, so M = 0.64 ÷ 0.0100 = 64 g mol−1, which matches SO2 (32 + 32).

7. 1.0 g samples of four gases are taken at STP. Which occupies the largest volume?

  1. A
    CH4
  2. B
    NH3
  3. C
    O2
  4. D
    CO2
Show answer

Answer: A. Equal masses: the gas with the smallest molar mass has the most moles, so the largest volume. CH4 (M = 16) beats NH3 (17), O2 (32) and CO2 (44).

8. How many molecules are present in 9 g of water?

  1. A
    6.02 × 1023
  2. B
    3.01 × 1023
  3. C
    1.505 × 1023
  4. D
    5.42 × 1024
Show answer

Answer: B. Moles = 9 ÷ 18 = 0.5 mol; molecules = 0.5 × 6.02 × 1023 = 3.01 × 1023. Multiplying the mass directly by NA gives 5.42 × 1024.

9. The molar volume of an ideal gas, 22.414 dm3, applies at

  1. A
    0 °C and 1 atm pressure
  2. B
    25 °C and 1 atm pressure
  3. C
    0 °C and 2 atm pressure
  4. D
    100 °C and 1 atm pressure
Show answer

Answer: A. STP means 273 K (0 °C) and 1 atm, where one mole of any ideal gas occupies 22.414 dm3. At 25 °C the volume would be larger.

10. 28 g of N2 and 3 g of H2 are mixed for N2 + 3H2 → 2NH3. Which is the limiting reactant?

  1. A
    N2, because it has the larger mass
  2. B
    H2, because it gives the smaller amount of product
  3. C
    neither; they are present in the exact mole ratio
  4. D
    N2, because fewer moles of it are present
Show answer

Answer: B. N2 = 1 mol could give 2 mol NH3; H2 = 1.5 mol could give only 1 mol NH3. The reactant giving less product is limiting, even though more moles of it are present.

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Ways to practise this chapter

Basic concepts: questions students ask

How many Basic concepts MCQs are there?

30, each with the answer and a short explanation, across 3 topics: Atoms, molecules, ions and isotopes, The mole and Avogadro's number, Stoichiometry, limiting reactant and yield. Every chapter test draws ten of them, so you can take it many times.

Is the FSc Part 1 Chemistry chapter 1 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

Can I read the explanations in Urdu?

Yes. In practice mode and on your results you can switch the explanations to Urdu.

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