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6. Over 20% of the crude oil refined at Whitingate in Cork Harbour in 2010 was imported from Libya - Leaving Cert Chemistry - Question 6 - 2011
Question 6
6. Over 20% of the crude oil refined at Whitingate in Cork Harbour in 2010 was imported from Libya. Libyan crude oil is particularly valued because of its rich light... show full transcript
Worked Solution & Example Answer:6. Over 20% of the crude oil refined at Whitingate in Cork Harbour in 2010 was imported from Libya - Leaving Cert Chemistry - Question 6 - 2011
Step 1
What is the nature of the chemicals that make up the bulk of crude oil?
Answer
The majority of crude oil is composed of hydrocarbons, specifically compounds primarily made up of carbon (C) and hydrogen (H). These hydrocarbons can include various types of alkanes and are classified based on their structure.
Step 2
Describe with the aid of a labelled diagram how crude oil is separated into useful substances in an oil refinery.
Answer
Crude oil undergoes a process called fractional distillation in an oil refinery. It is first heated in a fractionating column, where it vaporizes. As the vapor rises, it cools and condenses at different levels based on the boiling points of the various hydrocarbons. The lighter fractions, which have lower boiling points, condense at higher levels, while heavier fractions condense lower in the column. A labeled diagram should include the heating source, the fractionating column, and the various outlets for different products like petrol and diesel.
Step 3
What is catalytic cracking? Why is it carried out in oil refining?
Answer
Catalytic cracking is a method used to break down larger hydrocarbon molecules into smaller, more valuable products by using heat and a catalyst. This process is important in refining because it helps produce shorter chain hydrocarbons, which are in higher demand for fuel applications, such as petrol.
Step 4
Describe another method by which large quantities of hydrogen can be obtained from water.
Answer
Hydrogen can be obtained from water using electrolysis, a process where an electric current is passed through water to separate it into hydrogen and oxygen gases. This method is considered sustainable, especially when powered by renewable energy sources.
Step 5
Calculate the heat of this steam reforming reaction given that the heats of formation of methane, steam and carbon monoxide are –74.6, –242 and –111 kJ mol–1 respectively.
Answer
To calculate the heat of the steam reforming reaction:
ightarrow ext{CO}(g) + 3 ext{H}_2(g)$$ We apply the following formula: $$ ext{ΔH} = ext{ΣΔH f (products)} - ext{ΣΔH f (reactants)}$$ Where: - ΔH f of CH₄ = -74.6 kJ/mol - ΔH f of H₂O = -242 kJ/mol - ΔH f of CO = -111 kJ/mol - ΔH f of H₂ = 0 kJ/mol (elements in their standard state) Calculating: $$ ext{ΔH} = [(-111) + 0] - [(-74.6) + (-242)]$$ $$ ext{ΔH} = -111 - (-316.6)$$ $$ ext{ΔH} = 205.6 ext{ kJ mol}^{-1}$$