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You have performed first-hand investigations on water samples using qualitative and quantitative analyses - HSC - SSCE Chemistry - Question 21 - 2004 - Paper 1
Question 21
You have performed first-hand investigations on water samples using qualitative and quantitative analyses. (a) Distinguish between qualitative analysis and quantita... show full transcript
Worked Solution & Example Answer:You have performed first-hand investigations on water samples using qualitative and quantitative analyses - HSC - SSCE Chemistry - Question 21 - 2004 - Paper 1
Step 1
Distinguish between qualitative analysis and quantitative analysis.
Answer
Qualitative analysis focuses on identifying the components or substances present in a sample without measuring their exact amounts. For example, detecting the presence of chloride ions using specific reagents would fall under qualitative analysis.
On the other hand, quantitative analysis measures the concentration or amount of a particular substance in a sample. It provides numeric data on how much of a component exists, such as determining the exact concentration of nitrate ions in water.
Step 2
Describe TWO factors that affect the concentrations of ions in natural bodies of water.
Answer
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Geological Factors: The geological composition of the surrounding land affects the mineral runoff that enters bodies of water. Areas with limestone or salt deposits may have higher concentrations of calcium or sodium ions due to weathering and erosion processes.
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Anthropogenic Activities: Human activities such as agriculture and industrial processes can significantly impact ion concentrations. Fertilizers runoff can lead to increased levels of nitrate and phosphate ions, while pollutants from industrial discharges can alter the ionic composition of natural waters.
Step 3
Complete the following table to show how the anions listed can be identified.
Answer
| Anion | Reagent | Observations if anion is present |
|---|---|---|
| Cl^- | Silver nitrate (AgNO₃) | Formation of a white precipitate (AgCl) |
| PO₄^{3-} | Ammonium molybdate | Formation of a yellow precipitate |
| SO₄^{2-} | Barium chloride (BaCl₂) | Formation of a white precipitate (BaSO₄) |