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Poly(propenenitrile) is an addition polymer - OCR Gateway - GCSE Chemistry - Question 20 - 2019 - Paper 4
Question 20
Poly(propenenitrile) is an addition polymer. Look at the flow chart. It shows how poly(propenenitrile) is made from crude oil. crude oil → fractional distillation →... show full transcript
Worked Solution & Example Answer:Poly(propenenitrile) is an addition polymer - OCR Gateway - GCSE Chemistry - Question 20 - 2019 - Paper 4
Step 1
Explain how fractional distillation separates the hydrocarbons, in terms of intermolecular forces.
Answer
Fractional distillation is a method that relies on the differences in boiling points of the hydrocarbons present in crude oil. As the mixture is heated, the components with lower boiling points vaporize first and ascend the distillation column.
In the column, the temperature decreases as you move up, leading to condensation of the vapor at different heights corresponding to specific boiling points. The intermolecular forces, primarily Van der Waals forces, play a crucial role here. Hydrocarbons with weaker intermolecular forces (like those with shorter carbon chains) have lower boiling points and thus vaporize at lower temperatures. Consequently, they are collected at higher points in the column, while those with stronger intermolecular forces remain condensed at lower levels. This separation continues until all fractions have been collected based on their boiling point ranges.
Step 2
How can you tell from the displayed formula that propenenitrile is an unsaturated compound?
Answer
Propenenitrile has the molecular structure H2C=CH-C≡N. The presence of the double bond (C=C) between the two carbon atoms indicates that it is an unsaturated compound, as unsaturation is characterized by the presence of double or triple bonds. Additionally, unsaturated compounds can undergo addition reactions, which is a feature associated with alkenes and alkynes. Thus, the displayed formula clearly shows that propenenitrile is unsaturated due to the double bond.