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5 (c) Some fractions from crude oil contain large hydrocarbon molecules - AQA - GCSE Chemistry - Question 5 - 2015 - Paper 1
Question 5
5 (c) Some fractions from crude oil contain large hydrocarbon molecules. 5 (c) (i) Hydrocarbon molecules, such as decane, can be cracked to produce smaller, more us... show full transcript
Worked Solution & Example Answer:5 (c) Some fractions from crude oil contain large hydrocarbon molecules - AQA - GCSE Chemistry - Question 5 - 2015 - Paper 1
Step 1
Hydrocarbon molecules, such as decane, can be cracked to produce smaller, more useful molecules. Write the correct formula of the third product to complete the chemical equation.
Answer
The third product in the cracking of decane (C10H22) is ethylene, which has the formula C2H4. Hence, the complete chemical equation is:
Step 2
Pentene is used to produce poly(pentene). Complete the equation and the displayed structure of poly(pentene).
Answer
The equation for the polymerization of pentene is:
n \text{C}_{5} ext{H}_{10} \rightarrow \text{[-C}_{5} ext{H}_{10}-]_{n}}
The displayed structure of poly(pentene) shows repeating units of pentene linked together. Here is a simplified version:
H H
| |
C - C
| |
C - C
| |
C3H7
The repeating unit consists of carbon-carbon bonds and hydrogen atoms.
Step 3
Step 4
Describe how crude oil is separated into fractions.
Answer
Crude oil is separated into fractions through the process of fractional distillation. The oil is heated to evaporate the different hydrocarbons. As the vapor rises through the column, it cools. Components with lower boiling points reach the top while those with higher boiling points condense lower down the column, allowing for separation based on their boiling points.
Step 5
Suggest how the use of a suspension of limestone decreases one of the environmental impacts that the waste gases would cause.
Answer
The suspension of limestone in water neutralizes acids such as sulfur dioxide and carbon dioxide in the waste gases. This process reduces the formation of acid rain, which is caused by these gases reacting with moisture in the atmosphere.