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Hard water contains dissolved solids - Edexcel - GCSE Chemistry - Question 3 - 2017 - Paper 1
Question 3
Hard water contains dissolved solids. a) (i) Describe how to find the mass of dissolved solid in a 25 cm³ sample of hard water. (ii) A different 25 cm³ sample of a... show full transcript
Worked Solution & Example Answer:Hard water contains dissolved solids - Edexcel - GCSE Chemistry - Question 3 - 2017 - Paper 1
Step 1
Describe how to find the mass of dissolved solid in a 25 cm³ sample of hard water.
Answer
To find the mass of dissolved solid in a 25 cm³ sample of hard water, follow these steps:
- Determine the mass of an empty evaporating basin by weighing it on a balance.
- Pour 25 cm³ of hard water into the basin. Use a measuring cylinder for accuracy.
- Heat the basin to evaporate the water. This can be done either on a Bunsen burner or using an electric heater. Ensure that all the water evaporates.
- Weigh the basin again after all water has evaporated, and take note of the new mass.
- Subtract the mass of the empty basin from the mass of the basin with the solid. The result is the mass of the dissolved solid.
Step 2
Calculate the concentration of X in the solution, in g dm⁻³.
Answer
To calculate the concentration of dissolved solid X in the solution, use the formula:
ext{Concentration (g dm}^{-3} ext{)} = rac{ ext{mass of solute (g)}}{ ext{volume of solution (dm}^3 ext{)}}
For the given question:
- The mass of solid X is 0.6 g.
- The volume of the solution is 25 cm³, which is equal to 0.025 dm³.
Plugging in the values:
Step 3