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This question is about gold and compounds of gold - AQA - GCSE Chemistry Combined Science - Question 6 - 2020 - Paper 1
Question 6
This question is about gold and compounds of gold. In the alpha particle scattering experiment alpha particles are fired at gold foil. Alpha particles are positivel... show full transcript
Worked Solution & Example Answer:This question is about gold and compounds of gold - AQA - GCSE Chemistry Combined Science - Question 6 - 2020 - Paper 1
Step 1
What two conclusions can be made from the results?
Answer
- Atoms have a positively charged nucleus.
- Mass is concentrated in the nucleus in the centre of atoms.
These conclusions reflect the structure of the atom, where the nucleus contains the majority of the mass and carries a positive charge due to protons.
Step 2
What is the diameter of one gold atom in metres?
Answer
To find the diameter of one gold atom:
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First, convert the thickness of the gold foil from meters to atoms:
4.00 × 10⁻⁷ m / 2400 atoms = 1.66666 × 10⁻¹⁰ m.
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Now, round this to 3 significant figures:
Diameter of one gold atom = 1.67 × 10⁻¹⁰ m.
Step 3
Calculate the mass of chlorine needed to react with 0.175 g of gold.
Answer
To find the mass of chlorine needed:
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Calculate the moles of gold:
(moles Au = rac{0.175}{197}) = 0.000888 moles.
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From the reaction, 2 moles of Au react with 3 moles of Cl₂, hence:
(moles Cl₂ = 0.000888 × rac{3}{2}) = 0.00133 moles.
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Calculate the mass of chlorine:
(mass Cl₂ = moles Cl₂ × 71) = 0.0946 g.
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Convert grams to milligrams:
(0.0946 g = 94.6 mg).