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Aqueous solutions of ammonia, ethylamine and phenylamine are prepared - AQA - A-Level Chemistry - Question 24 - 2018 - Paper 3
Question 24
Aqueous solutions of ammonia, ethylamine and phenylamine are prepared. Each solution has the same concentration. Which is the correct order for the pH values of the... show full transcript
Worked Solution & Example Answer:Aqueous solutions of ammonia, ethylamine and phenylamine are prepared - AQA - A-Level Chemistry - Question 24 - 2018 - Paper 3
Step 1
Which is the correct order for the pH values of these solutions?
Answer
To determine the correct order of the pH values for ammonia, ethylamine, and phenylamine, we need to consider their basicity and the resulting pH of their solutions:
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Ammonia: Ammonia () is a weak base that ionizes in water to form hydroxide ions. It has a relatively higher pH.
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Ethylamine: Ethylamine () is also a weak base but is stronger than ammonia due to the electron-donating effect of the ethyl group, which helps stabilize the positive charge on ammonium ion formed when it acts as a base.
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Phenylamine: Phenylamine (), on the other hand, is weaker than both ammonia and ethylamine. The phenyl group has a withdrawing effect, which makes it less basic than both ammonia and ethylamine.
Based on this analysis, the correct order for the pH values from highest to lowest is:
- Ammonia > Ethylamine > Phenylamine.
Therefore, the correct choice is (A).