Senior Secondary (HKDSE) · Chemistry

Catalysts; green chemistry (atom economy, pollution control): Practice Questions

5 multiple-choice questions marked as you go, and 5 written questions with worked solutions. All on Catalysts; green chemistry (atom economy, pollution control).

10 questions23 marksFree, no account

Question 1

1 mark

Which of the following statements about a catalyst is TRUE?

Question 2

1 mark

A chemical plant converts benzene (\(C_6H_6\)) into cyclohexane (\(C_6H_{12}\)) via catalytic hydrogenation:
\(C_6H_6(l) + 3H_2(g) \rightarrow C_6H_{12}(l)\)
Which of the following statements regarding the atom economy of this reaction is correct?

Question 3

1 mark

Which of the following describes a practice that aligns with the 'Use of Renewable Feedstocks' principle of green chemistry?

Question 4

1 mark

The atom economy of a chemical reaction is defined as a measure of:

Question 5

1 mark

Consider the synthesis of ethyl ethanoate (\(CH_3COOCH_2CH_3\)) from ethanoic acid (\(CH_3COOH\)) and ethanol (\(CH_3CH_2OH\)):
\(CH_3COOH + CH_3CH_2OH \rightarrow CH_3COOCH_2CH_3 + H_2O\)
Calculate the atom economy for the production of ethyl ethanoate.
(Relative atomic masses: H = 1.0, C = 12.0, O = 16.0)

Question 6

2 marks

How does a catalyst affect the reaction pathway of a chemical reaction?

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Question 7

3 marks

In the context of green chemistry, explain why a process with a high atom economy is generally preferred over one with a low atom economy.

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Question 8

5 marks

Compare the environmental implications of using a homogeneous catalyst versus a heterogeneous catalyst in an industrial process, from the perspective of green chemistry principles.

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Question 9

3 marks

The traditional synthesis of a specific organic compound often employs strong mineral acids as catalysts, which subsequently need to be neutralised, generating significant amounts of salt waste. A newly developed method utilizes an enzyme as a catalyst, operating under mild temperature and pH conditions, and producing no inorganic salt by-products.

Explain one advantage of using the enzyme catalyst in the new method from a green chemistry perspective, specifically focusing on pollution control.

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Question 10

5 marks

a) Explain how a catalyst increases the rate of a chemical reaction.

b) Acrylonitrile (\(C_3H_3N\)) is an important monomer used in the production of plastics. One industrial method involves the ammoxidation of propene (\(C_3H_6\)) using ammonia (\(NH_3\)) and oxygen (\(O_2\)). The balanced chemical equation is:
\(2C_3H_6(g) + 2NH_3(g) + 3O_2(g) \xrightarrow{catalyst} 2C_3H_3N(g) + 6H_2O(g)\)
Assuming acrylonitrile (\(C_3H_3N\)) is the sole desired product, calculate the atom economy of this reaction. Show your working. (Relative atomic masses: C=12.0, H=1.0, N=14.0, O=16.0)

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