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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 involves passing hard water through a column containing a resin. This resin is charged with sodium ions. As the hard water flows through the column, calcium and magnesium ions from the water are exchanged with sodium ions in the resin. This effectively removes the hardness-causing ions, resulting in softer water. It's important to note that the resin needs periodic replenishment with sodium ions to maintain its effectiveness.
Step 2
Method 2: Adding sodium carbonate (washing soda)
Answer
Adding sodium carbonate to hard water reacts with calcium and magnesium ions, forming insoluble calcium carbonate. This precipitate then settles out, reducing the mineral content of the water and therefore softening it. This method is relatively straightforward and can be done with minimal equipment.
Step 3
Comparison of advantages
Answer
The ion exchange method is highly effective and can continuously soften large volumes of water; however, it requires maintenance and periodic replacement of the resin. In contrast, adding sodium carbonate is simpler and can be done without specialized equipment, making it more accessible for everyday use. However, it may not be as efficient for very hard water compared to the ion exchange method.