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Alloys of gold are often used to make jewellery - Edexcel - GCSE Chemistry - Question 1 - 2020 - Paper 1
Question 1
Alloys of gold are often used to make jewellery. The purity of gold is measured in carats. Different alloys of gold have different carats. (a) Figure 1 shows the per... show full transcript
Worked Solution & Example Answer:Alloys of gold are often used to make jewellery - Edexcel - GCSE Chemistry - Question 1 - 2020 - Paper 1
Step 1
Explain why 18 carat gold is stronger than 24 carat gold.
Answer
18 carat gold contains a mix of metals such as silver and copper, which disrupt the structure of the gold. This variation in atomic size enhances the bond strength between layers, making it less prone to slipping or sliding compared to 24 carat gold, which is pure gold and more malleable.
Step 2
Determine the purity of the gold necklace in carats.
Answer
To find the purity in carats, use the formula:
ext{Purity (in carats)} = rac{ ext{mass of gold}}{ ext{mass of necklace}} imes 24
Substituting the values:
ext{Purity} = rac{2.9 ext{g}}{5.0 ext{g}} imes 24 = 13.8 ext{ carats}
Thus, the purity of the gold necklace is approximately 14 carats.
Step 3
Calculate the number of gold atoms in the ring.
Answer
To calculate the number of gold atoms in the ring, use the formula:
ext{Number of atoms} = rac{ ext{mass of gold}}{ ext{relative atomic mass}} imes ext{Avogadro's constant}
Substituting the values:
ext{Number of atoms} = rac{3.94 ext{g}}{197} imes 6.02 imes 10^{23} ext{ atoms/mol}
Calculating gives:
Thus, the number of gold atoms in the ring is approximately .