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This question is about acids - AQA - GCSE Chemistry - Question 9 - 2021 - Paper 1
Question 9
This question is about acids. Hydrogen chloride and ethanoic acid both dissolve in water. All hydrogen chloride molecules ionise in water. Approximately 1% of ethan... show full transcript
Worked Solution & Example Answer:This question is about acids - AQA - GCSE Chemistry - Question 9 - 2021 - Paper 1
Step 1
Which is the correct description of this solution?
Answer
The solution made by dissolving 1 g of hydrogen chloride in 1 dm³ of water is a dilute solution of a strong acid. This is because hydrogen chloride completely ionizes in water and the concentration is low given the amount of solute compared to the solvent.
Step 2
Step 3
Suggest two improvements to the method that would increase the accuracy of the result.
Answer
- Use a white tile underneath the conical flask to easily see the color change of the indicator, ensuring more precise endpoint detection.
- Repeat the titration several times and calculate the average to improve reliability and account for any inconsistencies.
Step 4
Calculate the mass of ethanoic acid (H₂C₂O₄) needed to make 250 cm³ of a solution with concentration 0.0480 mol/dm³.
Answer
To calculate the mass, first determine the number of moles required:
ext{Moles} = ext{Concentration} imes ext{Volume} = 0.0480 ext{ mol/dm}^3 imes rac{250 ext{ cm}^3}{1000} = 0.012 ext{ mol}
Now, use the relative formula mass to find the mass:
Step 5
Calculate the concentration of the sodium hydroxide solution in mol/dm³.
Answer
From the reaction, we know the ratio of moles of H₂C₂O₄ to NaOH is 1:2. Thus, the moles of sodium hydroxide are:
Now calculate the concentration:
ext{Concentration} = rac{ ext{Moles}}{ ext{Volume}} = rac{0.00144 ext{ mol}}{ rac{25.0}{1000} ext{ dm}^3} = 0.0576 ext{ mol/dm}^3