Spinach is a leafy green vegetable - Scottish Highers Chemistry - Question 11 - 2022
Question 11
Spinach is a leafy green vegetable.
(a) Fertilisers containing copper(II) ethanoate are used to supply spinach with copper ions.
Copper(II) ethanoate can be made b... show full transcript
Worked Solution & Example Answer:Spinach is a leafy green vegetable - Scottish Highers Chemistry - Question 11 - 2022
Step 1
Name the other products of this reaction.
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Answer
The other products of the reaction between copper(II) carbonate and ethanoic acid are water (H₂O) and carbon dioxide (CO₂).
Step 2
Write the ionic formula of copper(II) ethanoate.
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Answer
The ionic formula of copper(II) ethanoate is ext{Cu(CH}_3 ext{COO)}_2.
Step 3
Describe fully how 250 cm³ of a standard solution of oxalic acid could be prepared.
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To prepare a 250 cm³ standard solution of oxalic acid:
Accurately weigh the required mass of oxalic acid using a balance.
Add the solid to a small volume of distilled water in a beaker. Stir until the solid has completely dissolved.
Transfer the solution to a 250 cm³ volumetric flask using a funnel, rinsing the beaker and funnel with more distilled water to ensure all acid is transferred.
Add distilled water to the volumetric flask until the bottom of the meniscus is level with the 250 cm³ mark.
Step 4
Draw a diagram of a pipette suitable for measuring an accurate volume.
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Answer
A diagram of a graduated pipette is required, showing the scale and the narrow tip, indicating it is used for accurate measurements.
Step 5
State the colour change that would be observed at the end point in this titration.
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The colour change observed at the end point in this titration would be from pink to colourless as the acidic oxalic acid neutralizes the sodium hydroxide.
Step 6
State the term used to describe titration values within 0.2 cm³ of each other.
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The term used to describe titration values within 0.2 cm³ of each other is 'concordant'.
Step 7
Calculate the concentration, in mol/dm³, of the sodium hydroxide.
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Answer
To calculate the concentration of sodium hydroxide (NaOH):
Calculate moles of oxalic acid using the formula:
[ n = \frac{\text{mass}}{\text{molar mass}} = \frac{0.126 \text{ mol/dm}^3 \times 26.75 \text{ cm}^3}{1000} = 0.00337 \text{ moles} ]
From the balanced equation, it takes 2 moles of NaOH for every 1 mole of oxalic acid;
[ n\text{(NaOH)} = 2 \times 0.00337 = 0.00674 \text{ moles} ]
Using the volume of NaOH solution used in titration (25.0 cm³):
[ \text{Concentration} = \frac{n}{V} = \frac{0.00674 \text{ moles}}{0.025 \text{ dm}^3} = 0.2696 \text{ mol/dm}^3 \approx 0.27 \text{ mol/dm}^3 ]
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