Question detail
When phosphorus pentoxide (P2O5) reacts with water, what is the resulting product?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Properties of Period 3 elements and their oxides (A-level only)
Question
- A. Phosphoric acid (H3PO4)
- B. Phosphorous acid (H3PO3)
- C. Phosphine (PH3)
- D. Phosphoric anhydride (P4O10)
Answer
Phosphoric acid (H3PO4)
Explanation
The correct option is Phosphoric acid (H3PO4). Phosphoric acid (H3PO4) is the best answer because it directly supports the AQA A-Level Chemistry objective to explain reactions of Period 3 oxides with water. This reasoning is anchored to Period 3 oxides (A-level only) in Properties of Period 3 elements and their oxides (A-level only), and it separates Period 3 oxide from similar A-Level ideas rather than relying on a vague recall statement. Other options are weaker if they use the wrong evidence, calculation, mechanism, observation, unit, or conclusion for this subtopic.
Common mistake
Incorrect Reaction Type
Students often confuse the reactions of Period 3 oxides with water as only acid-base reactions, neglecting to mention the formation of acids or bases.
Clearly state the type of reaction occurring, such as 'When sodium oxide reacts with water, it forms sodium hydroxide, a strong base, while silicon dioxide reacts with water to form a weak acid, silicic acid.'. Keep the correction anchored to Period 3 oxides (A-level only) and the objective: Explain reactions of Period 3 oxides with water.
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