Polystyrene repeat unit molecular weight.

In summary, polystyrene is a synthetic polymer that is commonly used in packaging materials and household products. Its repeat unit has a molecular weight of about 104 grams per mole, making it a relatively lightweight material. Polystyrene is known for its insulating properties and durability, but it is also a major contributor to environmental pollution due to its slow decomposition rate. Efforts are being made to find more sustainable alternatives to polystyrene, such as biodegradable and recyclable materials.
  • #1
AndrewDe
Edit: thread moved from non HW forum.
I'm trying to calculate the unit molecular weight of polystyrene. I'm given the structure, and I have to count all the elements in the structure. To calculate the weight, I keep counting 8C & 7H. The correct answer is 8C +8H. I'm having a hard time deterring where the additional H is coming from.
 
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  • #3
Can you draw the unit and post it as a picture?
 
  • #4
Picture from the textbook.
 

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  • #5
Borek said:
Can you draw the unit and post it as a picture?
Posted a picture from the textbook. Sorry about the wrong thread posting.
 
  • #6
How many hydrogen atoms on the ring? How many hydrogen atoms on the side chain?
 
  • #7
Borek said:
How many hydrogen atoms on the ring? How many hydrogen atoms on the side chain?
I see 4 in the ring, and 3 in the structure. Idk where I'm leaving the other H atom off.
 
  • #8
There are 5 in the ring, one on each C except the C joined to the rest of unit..
 
  • #9
AndrewDe said:
I see 4 in the ring

And - as epenguin said - that's where you are wrong. You were probably mislead by the picture and the way it depicts the hydrogen atoms on the alkane chain.

Imagine just benzene - how many hydrogens on the ring? How many hydrogens will be left on a mono substituted ring?
 
  • #10
AndrewDe said:
Edit: thread moved from non HW forum.
I'm trying to calculate the unit molecular weight of polystyrene. I'm given the structure, and I have to count all the elements in the structure. To calculate the weight, I keep counting 8C & 7H. The correct answer is 8C +8H. I'm having a hard time deterring where the additional H is coming from.

The benzene ring has 6 carbons and 6 hydrogens. There side chain takes the place of only of the hydrogens on the ring, leaving only 5 hydrogens on the ring. The side chain has 3 hydrogens. So, add 3 hydrogens from the side chain + 5 hydrogens from the benzene ring = total 8 hydrogens.
 

1. What is the molecular weight of a polystyrene repeat unit?

The molecular weight of a polystyrene repeat unit (C8H8) is 104.15 g/mol.

2. How is the molecular weight of a polystyrene repeat unit calculated?

The molecular weight of a polystyrene repeat unit is calculated by adding together the atomic weights of each element present in the molecule. In the case of polystyrene, this would be 8 carbon atoms (8 x 12.01 = 96.08 g/mol) and 8 hydrogen atoms (8 x 1.01 = 8.08 g/mol), for a total of 104.15 g/mol.

3. Why is the molecular weight of a polystyrene repeat unit important in scientific research?

The molecular weight of a polystyrene repeat unit is important because it helps determine the physical and chemical properties of the polymer. It also allows scientists to accurately measure and control the amount of polystyrene used in experiments and industrial processes.

4. Does the molecular weight of a polystyrene repeat unit affect its properties?

Yes, the molecular weight of a polystyrene repeat unit can greatly affect its properties, such as its strength, flexibility, and solubility. Generally, a higher molecular weight leads to a stronger and more rigid polymer, while a lower molecular weight results in a more flexible and soluble polymer.

5. Can the molecular weight of a polystyrene repeat unit vary?

Yes, the molecular weight of a polystyrene repeat unit can vary depending on the manufacturing process and the desired properties of the final product. Polystyrene can also be chemically modified to change its molecular weight, which can alter its properties.

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