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CIE iGCSE Co-Ordinated Science C11.1 Formulas and terminology Exam Style Questions Paper 2

CIE iGCSE Co-Ordinated Science Paper 2 - All Chapters

Question

Which statements about air pollution are correct?

  1. Carbon monoxide is a toxic gas that is formed by the incomplete combustion of carbon-based fuels.
  2. Oxides of nitrogen damage buildings and are produced by impurities in carbon-based fuels.
  3. Sulfur dioxide produces acid rain and is formed by the combustion of fossil fuels.

A. 1, 2 and 3
B. 1 and 2 only
C. 1 and 3 only
D. 2 and 3 only

▶️ Answer/Explanation
Statement 1 is correct: carbon monoxide is a toxic gas produced by incomplete combustion of carbon-based fuels. Statement 2 is incorrect: oxides of nitrogen are produced from the reaction of nitrogen and oxygen in car engines at high temperatures, not from impurities in fuels. Statement 3 is correct: sulfur dioxide is produced by the combustion of fossil fuels containing sulfur impurities and causes acid rain. Therefore, statements 1 and 3 are correct.
✅ Answer: (C)

Question

What is a general formula for unsaturated hydrocarbons?

A. \(C_nH_{n+2}\)
B. \(C_{2n}H_{2n+2}\)
C. \(C_nH_{2n}\)
D. \(C_nH_{2n+2}\)

▶️ Answer/Explanation
Unsaturated hydrocarbons contain at least one carbon-to-carbon double bond; the simplest homologous series of unsaturated hydrocarbons is the alkenes, which have the general formula \(C_nH_{2n}\).
The formula \(C_nH_{2n+2}\) belongs to alkanes (saturated); \(C_nH_{2n}\) fits ethene (\(C_2H_4\)), propene (\(C_3H_6\)), etc., all of which contain one double bond and are unsaturated.
✅ Answer: (C)

Question

Which statements about limestone are correct?

  1. Its main constituent is calcium oxide.
  2. It can be used to manufacture lime.
  3. It thermally decomposes to release carbon dioxide.
  4. It is used to neutralise alkaline soils.

A. \(1\) and \(2\)  
B. \(1\) and \(4\)  
C. \(2\) and \(3\)  
D. \(3\) and \(4\)

▶️ Answer/Explanation
Limestone is mainly \(CaCO_3\), not \(CaO\), so statement \(1\) is wrong; heating gives \(CaCO_3 \rightarrow CaO + CO_2\), confirming statements \(2\) and \(3\).
Limestone is used to neutralise acidic soils, not alkaline ones, so statement \(4\) is incorrect.
✅ Answer: (C)

Question

The structures of four organic compounds, P, Q, R and S, are shown.

Which statements about P, Q, R and S are correct?

  1. P and Q have the same general formula.
  2. Q and R have similar chemical properties.
  3. R and S are members of the same homologous series.
  4. R and Q have the same molecular mass, \( M_r \).

A. 1 and 2
B. 1 and 3
C. 2 and 4
D. 3 and 4

▶️ Answer/Explanation
Statement 1 is correct because P and Q are both alkanes (pentane and 2-methylbutane) and have the same general formula CₙH₂ₙ₊₂. Statement 2 is incorrect because Q is an alkane (saturated) and R is a cycloalkane, which have different general formulas and chemical properties. Statement 3 is correct because R and S are both cycloalkanes (cyclopentane and cyclohexane) belonging to the same homologous series. Statement 4 is incorrect because Q (C₅H₁₂, Mᵣ = 72) and R (C₅H₁₀, Mᵣ = 70) have different molecular masses. Therefore, statements 1 and 3 are correct.
✅ Answer: (B)

Question

What is a general formula for unsaturated hydrocarbons?
(A) $C_{n}H_{n+2}$

(B) $C_{2n}H_{2n+2}$

(C) $C_{n}H_{2n}$

(D) $C_{n}H_{2n+2}$

▶️Answer/Explanation

Ans: C

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