Question
(a) The structures of four organic compounds, P, Q, R and S, are shown.
Answer the following questions about these structures.
Each structure may be used once, more than once or not at all.
(i) State which structure, P, Q, R or S, has a carboxylic acid functional group.[1]
(ii) State which structure, P, Q, R or S, is in the same homologous series as ethane.[1]
(iii) State which structure, P, Q, R or S, decolourises aqueous bromine.[1]
(iv) Deduce the molecular formula of structure Q to show the number of carbon, hydrogen and oxygen atoms.[1]
(b) Structure S is produced by cracking petroleum fractions.
(i) Complete the sentence using a word from the list.
acids alkenes alcohols nitrogen
During cracking, long-chain alkanes are converted to shorter chain alkanes and[1]
(ii) Cracking is an example of thermal decomposition.
State the meaning of the term thermal decomposition.[2]
(c) Link each petroleum fraction on the left to its use on the right.
The first one has been done for you.
Answer/Explanation
Ans:
(a)(i) Q
(a)(ii) S
(a)(iii) R
(a)(iv) C4H8O2
(b)(i) alkenes
(b)(ii) breakdown of a compound (1)
using heat / by heat (1)
(c) naphtha → making chemicals
lubricating fraction → waxes and polishes
kerosene → jet fuel
all 3 correct (2)
1 or 2 correct (1)
Question
The table shows the masses of some ions in a 1000cm3 sample of toothpaste.
(a) Answer these questions using only the information in the table.
(i) State which negative ion has the lowest mass in 1000cm3 of toothpaste.[1]
(ii) Name the compound that contains NH4+ and Cl–ions.[1]
(iii) Calculate the mass of phosphate ions in 250cm3 of toothpaste.
mass = g [1]
(b) Describe a test for sulfate ions.[2]
test
observations
(c) Toothpaste also contains cinnamal.
The structure of cinnamal is shown.
Deduce the formula of cinnamal to show the number of atoms of carbon, hydrogen and oxygen.[1]
(d) Cinnamal can be oxidised to a carboxylic acid.
(i) Draw the structure of a carboxylic acid functional group to show all of the atoms and all of the bonds. [1]
(ii) Ethanoic acid is a carboxylic acid.
Ethanoic acid reacts like a typical acid.
Complete the word equation for the reaction of ethanoic acid with sodium carbonate.
[2] [Total: 9]
Answer/Explanation
Ans:
(a)(i) Cl – / chloride
(a)(ii) ammonium chloride
(a)(iii) 6.1 (g)
(b) (acidify and) add barium nitrate (1)
white precipitate (1)
(c) C9H8O
(d)(i)
d)(ii) carbon dioxide (1)
water (1)
Question
The structure of malic acid is shown.
(a) (i) On the structure draw a circle around the alcohol functional group.
(ii) Deduce the formula of malic acid to show the number of carbon, hydrogen and oxygen atoms.
(b) When malic acid is heated it forms compound F.
The structure of compound F is shown.
Explain why compound F is described as unsaturated.
(c) Compound F can form polymers.
(i) State the meaning of the term polymer.
(ii) State the name of the polymer formed when ethene is polymerised.
(d) Ethanoic acid is a carboxylic acid.
Describe the observations made when dilute ethanoic acid reacts with:
magnesium ………………………………………………………………………………………………………………..
litmus solution. ……………………………………………………………………………………………………………
(e) The graph shows how the pH changes when dilute ethanoic acid is added slowly to aqueous sodium hydroxide.
(i) Deduce the pH of the aqueous sodium hydroxide before the addition of dilute ethanoic acid.
pH = …………………………
(ii) Deduce the volume of dilute ethanoic acid added when the pH is neutral.
………………………… \(cm^3\)
Answer/Explanation
Answer:
(a) (i) OH alcohol group cicled
(ii) \(C_4H_{6}O_5\)
(b) it has a C = C double bond
(c) (i) large molecules / long chain molecules / macromolecules (1)
built up from (many) small units / made from monomers (1)
(ii) poly(ethene)
(d) with Mg: fizzes / bubbles / effervescence (1)
litmus: turns red / turns pink (1)
(e) (i) pH 13
(ii) 18 (\(cm^3\))