CIE iGCSE Co-Ordinated Science C11.2 Naming organic compounds Exam Style Questions Paper 3
Question
(a) Fig. 11.1 shows the molecular structure of ethene.
i) State the total number of atoms in a molecule of ethene.
……………………………………
(ii) State the formula of ethene.
…………………………………………………………………………………………………………………….
(iii) Use Fig. 11.1 to explain why an ethene molecule is described as unsaturated.
………………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
(iv) State the chemical test for an unsaturated hydrocarbon.
Give the observations for a positive result.
test ……………………………………………………………………………………………………………………
observations ……………………………………………………………………………………………………….
(b) (i) State the two products of the complete combustion of ethene.
1 ……………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………….
(ii) Ethene is made from the breakdown of larger molecules in petroleum.
State the name of this process.
………………………………………………………………………………………………………………………….
(iii) Polymerisation of ethene produces poly(ethene).
Describe what happens to ethene molecules during polymerisation.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans : 11(a)(i) 6 ;
11(a)(ii) C2H4 ;
11(a)(iii) C=C double bond ;
11(a)(iv) aqueous bromine ;
orange to colourless ;
11(b)(i) carbon dioxide ;
water ;
11(b)(ii) cracking ;
11(b)(iii) join together / make a long chain ;
Question
(a) Ethanol has the formula C$_{2}$H$_{5}$OH.
Complete Fig. 5.1 to show the structure of an ethanol molecule.
Fig. 5.1
(b) Ethanol is used as a fuel.
(i) State one other use for ethanol.
…………………………………………………………………………………………………………………….
(ii) Write the word equation for the complete combustion of ethanol.
…………………………. + …………………………. …………………………. + ………………………….
(iii) The combustion of ethanol is an exothermic reaction.
State what is meant by an exothermic reaction.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
(c) Ethanol is made from ethene.
Ethene reacts at high temperatures with substance X in the presence of a catalyst.
(i) State the name of substance X.
…………………………………………………………………………………………………………………….
(ii) Describe the effect of a catalyst on chemical reactions.
………………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
(iii) State one other method of making ethanol.
…………………………………………………………………………………………………………………….
(d) Ethanol is a liquid at room temperature.
Describe the motion and separation of the particles in ethanol.
motion ………………………………………………………………………………………………………………………
separation …………………………………………………………………………………………………………………
▶️Answer/Explanation
Ans: 5(a)
C–O–H correct ;
all else correct ;
5(b)(i) solvent ;
5(b)(ii) ethanol + oxygen → carbon dioxide + water
ethanol and oxygen ;
carbon dioxide and water ;
5(b)(iii) thermal energy released ;
5(c)(i) steam / water ;
5(c)(ii) increase rate of reaction ;
5(c)(iii) fermentation ;
5(d) random (motion) ;
touching ;
Question
Methane, CH4, is a hydrocarbon.
(a) (i) Methane is the main constituent of a fossil fuel.
State the name of this fossil fuel.
(ii) State the name of the type of bonding in a molecule of methane.
(iii) Complete the dot-and-cross diagram in Fig. 8.1 to show the bonding in a molecule of
methane. You only need to show the outer-shell electrons.
(b) The complete combustion of methane makes carbon dioxide and water.
(i) Balance the symbol equation for the complete combustion of methane.
CH4 + ……………O2 → CO2 + ……………H2O
(ii) Methane is oxidised in this reaction. Explain how the symbol equation shows that methane is oxidised.
(iii) During the incomplete combustion of methane carbon monoxide is made.
Describe one adverse effect of carbon monoxide on the health of humans.
(c) Carbon is an element. Methane is a compound.
Describe the difference between an element and a compound by completing the sentences
using only the words elements or compounds. …………………………. are pure substances consisting only of atoms, all of which have the same number of protons in their nuclei. …………………………. are chemical substances composed of two or more …………………………. held together by chemical bonds.
▶Answer/Explanation
Ans:
8(a)(i) natural gas ;
8(a)(ii) covalent ;
8(a)(iii) one pair of shared electrons ;
four pairs of electrons and all else correct ;
8(b)(i) 2 O2 ;
2 H2O ;
8(b)(ii) gains / reacts with oxygen ;
8(b)(iii) toxic;
8(c) elements compounds elements ;
Question
Petroleum is a raw material for the production of useful substances.
Fig. 8.1 shows three processes, X, Y and Z, used to make ethanol.
(a) Identify process X and process Y.
process X ………………………………………………………………………………………………………………….
process Y ………………………………………………………………………………………………………………….
(b) State the substance added to ethene during process Z to make ethanol.
…………………………………………………………………………………………………………………………………
(c) Ethene is a hydrocarbon.
Explain why ethene is described as a hydrocarbon.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(d) State the two products of the complete combustion of ethene.
1 ………………………………………………………………………………………………………………………………
2 ………………………………………………………………………………………………………………………………
(e) Complete Fig. 8.2 to show the structure of an ethanol molecule, C2H5OH. Include all the atoms and bonds.
Fig. 8.2
▶️Answer/Explanation
Ans: 8(a) process X – fractional distillation ;
process Y – cracking ;
8(b) steam ;
8(c) contains carbon and hydrogen (atoms) ;
only ;
8(d) carbon dioxide ;
water ;
8(e)
O – H attached to carbon ;
all else correct ;
Question
Ethane, ethene and ethanol are carbon compounds.
(a) Complete Table 11.1.
▶️Answer/Explanation
11(a) ethene
ethanol
ethane
(b) Fig. 11.1 is a diagram of an industrial process to make ethanol.
(i) Identify substance X.
▶️Answer/Explanation
Substance X is steam (H2O).
(ii) Suggest why a catalyst is needed in the reaction vessel.
▶️Answer/Explanation
A catalyst is needed to increase the rate of the reaction without being consumed in the process. It lowers the activation energy required for the reaction to proceed, making the process more efficient.
(c) Fig. 11.2 shows apparatus and materials a student uses to make ethanol in a school laboratory.
(i) State the name of this process.
▶️Answer/Explanation
The process is called fermentation.
(ii) The student observes a gas bubbling into solution S. Solution S becomes milky. Identify the gas and solution S.
▶️Answer/Explanation
The gas is carbon dioxide (CO2), and solution S is limewater (Ca(OH)2).
(d) Fig. 11.3 shows apparatus the student uses to measure the change in mass when ethanol burns in air.
The mass of the burner and ethanol decreases during the experiment. Suggest why.
▶️Answer/Explanation
The mass decreases because ethanol undergoes combustion, producing carbon dioxide (CO2) and water (H2O) as gaseous products. These gases escape into the air, leading to a loss of mass from the system.