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Magnesium and calcium are in group 2 of the periodic table - Edexcel - GCSE Chemistry - Question 2 - 2016 - Paper 1
Question 2
Magnesium and calcium are in group 2 of the periodic table. They are less reactive than the metals in group 1. (a) Calcium reacts with water to form calcium hydroxi... show full transcript
Worked Solution & Example Answer:Magnesium and calcium are in group 2 of the periodic table - Edexcel - GCSE Chemistry - Question 2 - 2016 - Paper 1
Step 1
Describe what would be seen when a piece of calcium is dropped into a container of water.
Answer
When a piece of calcium is dropped into a container of water, it will react vigorously, producing hydrogen gas. Bubbles of hydrogen will form as a gas is released, and the calcium may fizz as it dissolves. The water will also become cloudy due to the formation of calcium hydroxide, which may create a white precipitate in the water.
Step 2
Step 3
Suggest an explanation, in terms of their electronic configurations, why calcium is more reactive than magnesium.
Answer
Calcium is more reactive than magnesium because it has a higher atomic number and an additional electron shell. The electronic configuration of magnesium is 2.8.2, while that of calcium is 2.8.8.2. The outermost electron in calcium is further away from the nucleus, making it easier to lose compared to magnesium's outermost electrons, which are more strongly attracted to the nucleus. This increased distance and shielding effect enable calcium to react more readily with other substances.
Step 4
Calculate the empirical formula of calcium bromide.
Answer
To calculate the empirical formula of calcium bromide, follow these steps:
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Divide mass by relative atomic mass:
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For Calcium:
0.2 ext{ g} imes rac{1 ext{ mol}}{40 ext{ g}} = 0.005 ext{ mol}
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For Bromine:
0.8 ext{ g} imes rac{1 ext{ mol}}{80 ext{ g}} = 0.01 ext{ mol}
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Calculate simplest ratio:
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Ratio of Ca to Br is
rac{0.005}{0.005} : rac{0.01}{0.005} = 1 : 2
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Express ratio correctly as empirical formula:
- The empirical formula of calcium bromide is CaBr₂.