CIE iGCSE Co-Ordinated Science C11.1 Formulas and terminology Exam Style Questions Paper 3
Question
(a) The proton numbers and nucleon numbers of carbon and hydrogen are shown in Table 11.1
i) State the number of neutrons in a carbon atom and the number of neutrons in a hydrogen atom.
(ii) State the number of electrons in a carbon atom.
(b) (i) State the difference between a saturated hydrocarbon and an unsaturated hydrocarbon.
(ii) Aqueous bromine is used to show the difference between a saturated hydrocarbon and an unsaturated hydrocarbon.
Describe the result of the test with a saturated hydrocarbon.
(c) Fig. 11.1 shows the apparatus used for the catalytic cracking of a saturated hydrocarbon.
(i) State the purpose of the catalyst in the cracking of a saturated hydrocarbon.
(ii) Cracking is an endothermic reaction.
State what is meant by an endothermic reaction.
(d) The complete combustion of hydrocarbons produces the greenhouse gas carbon dioxide.
(i) Name one other greenhouse gas.
(ii) Identify the gas in the air that reacts with hydrocarbons during combustion.
(iii) Carbon dioxide is one of the gases found in clean air.
State the name of the two gases found in clean air in the greatest proportions.
▶️Answer/Explanation
Ans : 11(a)(i) carbon = 6 ;
hydrogen = 0 ;
11(a)(ii) 6 ;
11(b)(i) unsaturated has a C=C double bond ;
11(b)(ii) aqueous bromine remains orange ;
11(c)(i) speed up the reaction ;
11(c)(ii) temperature decreases / thermal energy is absorbed (from the surroundings) ;
11(d)(i) methane ;
11(d)(ii) oxygen ;
11(d)(iii) oxygen ;
nitrogen ;
Question
Table 5.1 shows five compounds, A, B, C, D and E, and the formula of each compound.
(a) (i) State the compound from Table 5.1 that is an unsaturated hydrocarbon.
…………………………………………………………………………………………………………………….
(ii) Describe the chemical test that distinguishes between a saturated hydrocarbon and an
unsaturated hydrocarbon and state the results for each.
test ……………………………………………………………………………………………………………………
………………………………………………………………………………………………………………………….
result for a saturated hydrocarbon ………………………………………………………………………
………………………………………………………………………………………………………………………….
result for an unsaturated hydrocarbon …………………………………………………………………
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
(b) (i) State the name of the two compounds from Table 5.1 that are possible products of the
combustion of compound E.
1 ……………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………….
(ii) State the name of the compound made when compound D reacts with steam.
…………………………………………………………………………………………………………………………
(iii) State the name of the polymer made using compound D as a monomer.
…………………………………………………………………………………………………………………….
(iv) Draw the structure of compound E, C$_{2}$H$_{6}$.
(c) State the names of the two most common greenhouse gases from Table 5.1.
………………………………………………………… and …………………………………………………………
▶️Answer/Explanation
Ans: 5(a)(i) D ;
5(a)(ii) (aqueous) bromine ;
saturated – stays orange ;
unsaturated – goes colourless ;
5(b)(i) carbon monoxide ;
carbon dioxide ;
5(b)(ii) ethanol ;
5(b)(iii) poly(ethene) ;
5(b)(iv) C–C single bond ;
3 hydrogens each attached to a different carbon atom ;
5(c) carbon dioxide and methane ;
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
Fig. 11.1 shows the structures of five compounds A, B, C, D, and E.
(a) Use the letters A–E to identify all the hydrocarbon molecules.
▶️Answer/Explanation
Answer: B, C, and D
Explanation: Hydrocarbons are compounds that contain only hydrogen and carbon atoms. From the structures shown in Fig. 11.1, compounds B, C, and D consist solely of hydrogen and carbon atoms, making them hydrocarbons.
(b) Use the letters A–E to identify the two products of the complete combustion of a hydrocarbon.
▶️Answer/Explanation
Answer: A and E
Explanation: The complete combustion of a hydrocarbon produces carbon dioxide (CO₂) and water (H₂O). From the structures shown in Fig. 11.1, compound A represents carbon dioxide (CO₂), and compound E represents water (H₂O).
(c) Use Fig. 11.1 to name one greenhouse gas.
▶️Answer/Explanation
Answer: Carbon dioxide (CO₂) or methane (CH₄)
Explanation: Greenhouse gases trap heat in the Earth’s atmosphere. From the structures shown in Fig. 11.1, compound A is carbon dioxide (CO₂), which is a well-known greenhouse gas. Additionally, compound D could represent methane (CH₄), another potent greenhouse gas.
(d) Draw a dot-and-cross diagram to show the bonding in molecule E.
Only show the outer shell electrons.
▶️Answer/Explanation
Answer:
Explanation: Molecule E is water (H₂O). In the dot-and-cross diagram, oxygen has six outer shell electrons, and each hydrogen atom has one. Oxygen shares one electron with each hydrogen atom, forming two covalent bonds. The remaining four electrons on oxygen are lone pairs.
(e) Compound D is an unsaturated compound.
- State what is meant by the term unsaturated compound.
- Name the process that produces smaller unsaturated hydrocarbon molecules from large saturated hydrocarbon molecules.
- State the chemical test for an unsaturated hydrocarbon and give the observation for a positive result.
▶️Answer/Explanation
Answer:
- An unsaturated compound contains at least one carbon-carbon double or triple bond.
- The process is called cracking.
- The chemical test is the addition of aqueous bromine (bromine water). A positive result is indicated by the bromine water changing from orange to colorless.
Explanation:
- Unsaturated compounds have double or triple bonds between carbon atoms, which allow them to undergo addition reactions.
- Cracking is a process where large hydrocarbon molecules are broken down into smaller, more useful molecules, often producing unsaturated hydrocarbons.
- Bromine water reacts with the double bonds in unsaturated hydrocarbons, causing the orange color of bromine to disappear, indicating the presence of an unsaturated compound.