Working Out Repeat Units Flashcards

1️⃣ Familiarise yourself with the flashcards:

  • Look through all the flashcards to see what's on both sides.
  • Make sure you understand the information on each card. If something's unclear, click the link to the revision notes at the bottom of the page for more details.

2️⃣ Test yourself:

  • Look at the question or prompt on each card and try to remember the answer before flipping it over.
  • Check the answer and make a note of any cards you find challenging and need to go over more.

3️⃣ Consistently Review and Practice:

  • Use spaced repetition: spend more time on the cards you struggle with and go over them more often.
  • Regularly review all the flashcards to help you better understand and retain the information over time.

Note: We may include questions that have multiple correct answers. It's useful to remember specific examples to understand these concepts better.

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What is a repeat unit in a polymer?

A repeat unit is the smallest group of atoms that repeats again and again along a polymer chain.

What do the square brackets around a group of atoms in a polymer formula show?

The square brackets show the repeat unit of the polymer.

What does the small letter n after the square brackets in a polymer formula mean?

The letter n means there are many repeat units joined together in a very long chain.

How do you draw the repeat unit of an addition polymer from its alkene monomer?

Change the C=C double bond to a C–C single bond, keep all the attached atoms the same, put the unit in square brackets, and draw bonds passing through the brackets with an n outside.

What happens to the C=C double bond in an alkene monomer when an addition polymer forms?

The C=C double bond opens up and becomes a C–C single bond in the repeat unit.

What is the repeat unit of poly(ethene) formed from ethene, CH2=CH2?

The repeat unit is –CH2–CH2–, shown in square brackets with a single bond between the carbons and an n outside.

How can you find the repeat unit when you are given a long section of a polymer chain?

Look for the smallest section of the chain that repeats in the same pattern, then draw that section once in square brackets with bonds going out of each end.

How do you work out the monomer from the repeat unit of an addition polymer?

Remove the square brackets, change the central C–C single bond back to a C=C double bond, and keep all the attached atoms the same.

The repeat unit of a polymer is –CH2–CHCl–. What is the monomer?

The monomer is chloroethene, CH2=CHCl.

How can you tell if a displayed structure is a monomer or a polymer repeat unit?

A monomer has a C=C double bond and no square brackets, while a polymer repeat unit has a C–C single bond inside square brackets with an n after them.