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AQA GCSE · Question 04.4 · Chemical analysis
The student calculated that the Rₑ value of the orange dye in the experiment shown in Figure 5 was 0.48.
Calculate the distance moved by the solvent front when the orange dye had moved 5.4 cm.
The student calculated that the Rₑ value of the orange dye in the experiment shown in Figure 5 was 0.48.
Calculate the distance moved by the solvent front when the orange dye had moved 5.4 cm.
How to approach this question
This question requires you to use and rearrange the formula for the Rₑ value.
1. Recall or write down the formula: Rₑ = (distance moved by spot) / (distance moved by solvent).
2. You are given the Rₑ value (0.48) and the distance moved by the spot (5.4 cm). You need to find the distance moved by the solvent front.
3. Rearrange the formula to solve for the distance moved by the solvent front.
4. Substitute the numbers into your rearranged formula and calculate the answer.
Full Answer
The Rₑ (retardation factor) value in chromatography is a ratio calculated using the formula:
Rₑ = distance moved by the substance (the spot) / distance moved by the solvent front.
In this problem, we are given:
- Rₑ = 0.48
- Distance moved by substance = 5.4 cm
We need to find the distance moved by the solvent front. We must rearrange the formula:
Distance moved by solvent front = Distance moved by substance / Rₑ
Now, substitute the values:
Distance moved by solvent front = 5.4 cm / 0.48
Distance moved by solvent front = 11.25 cm
The solvent front moved 11.25 cm.
Common mistakes
✗ Incorrectly rearranging the formula (e.g., multiplying 5.4 by 0.48).
✗ Dividing the numbers the wrong way up (0.48 / 5.4).
✗ Calculation errors.
Practice the full AQA GCSE Chemistry Higher Tier Paper 2
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