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In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate - AQA - GCSE Chemistry - Question 4 - 2015 - Paper 3
Question 4
In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate. Hard water can be softened... show full transcript
Worked Solution & Example Answer:In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate - AQA - GCSE Chemistry - Question 4 - 2015 - Paper 3
Step 1
Method 1: Ion exchange
Answer
The ion exchange method softens hard water by replacing calcium and magnesium ions with sodium ions. In this process, hard water passes through a resin material containing sodium ions. As the water flows through the ion exchange column, calcium and magnesium ions are exchanged for sodium ions, thereby producing soft water. This method requires periodic replenishment of sodium ions and is highly effective at lowering water hardness.
Step 2
Method 2: Adding sodium carbonate (washing soda)
Answer
In this method, sodium carbonate is added to hard water, where it reacts with calcium and magnesium ions to form insoluble calcium carbonate. This precipitate is then removed from the water, effectively softening it. This method is straightforward and can be implemented easily, but it may not be as efficient in situations with high levels of hardness.
Step 3
Comparison of advantages
Answer
The ion exchange method is effective for continuous softening and can handle varying levels of water hardness. However, it requires regular maintenance to replenish sodium ions, making it potentially more costly over time. On the other hand, adding sodium carbonate is simple and inexpensive, but it may not adequately remove all hardness in extremely hard water. Each method has its merits, depending on the specific water quality and application needs.