These questions revise the lessons in polymers. Use Ar values: H = 1, C = 12, O = 16, Cl = 35.5.
Try each question on paper before opening the answer.
Questions
Question 1
Which of these can form an addition polymer: ethane, ethene, propene? Give a reason.
Answer
Ethene and propene can, because each has a C=C double bond that opens during polymerisation. Ethane has only single bonds.
Question 2
Draw the repeating unit of poly(propene).
Answer
Propene is CH₂=CH–CH₃. The repeating unit is –CH₂–CH(CH₃)–, with a single bond between the carbons and open ends.
Question 3
A poly(propene) sample has a relative molecular mass of 42 000. How many repeating units does it contain?
Answer
The monomer C₃H₆ has Mr = 36 + 6 = 42. So n = 42 000 ÷ 42 = 1000.
Question 4
State one difference between addition and condensation polymerisation that can be seen in the products.
Answer
Addition gives only the polymer. Condensation gives the polymer and a small molecule, such as water, at each link.
Question 5
Explain why vulcanised rubber is harder and more elastic than natural rubber.
Answer
Sulfur atoms form cross-links between the long rubber chains. The chains cannot slide apart easily, and they are pulled back after stretching. So the rubber is harder and springs back.
Question 6
A reusable drinking bottle costs RM15 and is used 300 times. A disposable bottle costs RM0.80 per use. Which has the lower cost per use?
Answer
Reusable bottle: 15 ÷ 300 = RM0.05 per use. The disposable bottle costs RM0.80 per use. The reusable bottle is cheaper per use by RM0.75.
Question 7
In forming a condensation polymer, 0.50 mol of links form. One water molecule is released per link. What mass of water is released? (H = 1, O = 16.)
Answer
Moles of water = 0.50 mol. Mass = 0.50 × 18 = 9.0 g.
Question 8
Give one benefit and one drawback of using a synthetic polymer for food packaging, and state a conclusion.
Answer
Benefit: it is light and keeps food clean and dry. Drawback: most synthetic polymers persist as waste for a long time. A fair conclusion is that packaging is worthwhile if it is reused or recycled, which reduces the waste per use.
If you got these wrong
- Questions 1 and 4: revise distinguishing addition and condensation polymerisation.
- Questions 2 and 3: revise identifying repeating units.
- Question 5: revise connecting polymer structure with properties.
- Questions 6 and 8: revise evaluating uses and environmental trade-offs.
Log the failing step in the mistake log and paper error review, or plan a timed round with the timed original practice session builder. To practise with a teacher, see online one-to-one Chemistry tuition.