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step J pour the potassium hydroxide solution into a conical flask and add a few drops of indicator to this solution step K fill a burette with the dilute hydrochloric acid and record the initial reading from the burette step L use a measuring cylinder to obtain 25 cm³ of potassium hydroxide solution step M take a final reading from the burette and calculate the volume of the dilute hydrochloric acid reacted step N run the dilute hydrochloric acid from the burette into the conical flask until the indicator changes colour (i) Write the steps in the correct order - Edexcel - GCSE Chemistry - Question 4 - 2020 - Paper 1
Question 4
step J pour the potassium hydroxide solution into a conical flask and add a few drops of indicator to this solution step K fill a burette with the dilute hydroch... show full transcript
Worked Solution & Example Answer:step J pour the potassium hydroxide solution into a conical flask and add a few drops of indicator to this solution step K fill a burette with the dilute hydrochloric acid and record the initial reading from the burette step L use a measuring cylinder to obtain 25 cm³ of potassium hydroxide solution step M take a final reading from the burette and calculate the volume of the dilute hydrochloric acid reacted step N run the dilute hydrochloric acid from the burette into the conical flask until the indicator changes colour (i) Write the steps in the correct order - Edexcel - GCSE Chemistry - Question 4 - 2020 - Paper 1
Step 1
Write the steps in the correct order.
Answer
The correct order of the steps is as follows:
- K: fill a burette with the dilute hydrochloric acid and record the initial reading from the burette.
- J: pour the potassium hydroxide solution into a conical flask and add a few drops of indicator to this solution.
- N: run the dilute hydrochloric acid from the burette into the conical flask until the indicator changes colour.
- M: take a final reading from the burette and calculate the volume of the dilute hydrochloric acid reacted.
- L: use a measuring cylinder to obtain 25 cm³ of potassium hydroxide solution.
Step 2
Step 3
Explain why this new mixture was evaporated rather than the original mixture from the titration, to produce a pure sample of solid potassium chloride.
Answer
The new mixture was evaporated because the solution from the titration contains an indicator, which could contaminate the produced solid potassium chloride. By using the new mixture, free from the indicator, a purer sample is obtained.
Step 4
Calculate a percentage yield of this experiment.
Answer
The percentage yield can be calculated using the formula:
ext{Percentage Yield} = rac{ ext{Actual Yield}}{ ext{Theoretical Yield}} imes 100 Substituting the given values:
ext{Percentage Yield} = rac{0.84 ext{ g}}{0.70 ext{ g}} imes 100 = 120 ext{ %}
Step 5
Suggest a reason why the percentage yield was greater than the theoretical yield.
Answer
The percentage yield may be greater than the theoretical yield because the product could still contain some water, meaning that the actual mass measured includes excess moisture. Thus, the weight recorded is higher than what is theoretically expected.
Step 6
Calculate the atom economy for the production of potassium chloride from potassium hydroxide and hydrochloric acid.
Answer
To calculate the atom economy, use the formula:
ext{Atom Economy} = rac{ ext{Mass of desired product}}{ ext{Total mass of reactants}} imes 100 Mass of the desired product (KCl) = 74.5 g + 18.0 g (for water) = 92.5 g. Total mass of reactants = 56.0 g (KOH) + 36.5 g (HCl) = 92.5 g. Calculating atom economy:
ext{Atom Economy} = rac{74.5}{(56.0 + 36.5)} imes 100 = 80.5 ext{ %}