This question is about some of the elements in group 7 of the periodic table - Edexcel - GCSE Chemistry Combined Science - Question 5 - 2021 - Paper 1
Question 5
This question is about some of the elements in group 7 of the periodic table.
(a) Which row in the table correctly shows the colours and physical states of the elem... show full transcript
Worked Solution & Example Answer:This question is about some of the elements in group 7 of the periodic table - Edexcel - GCSE Chemistry Combined Science - Question 5 - 2021 - Paper 1
Step 1
Which row in the table correctly shows the colours and physical states of the elements at room temperature?
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Answer
The correct answer is D: iodine is a dark grey solid and bromine is a red-brown liquid. Other options contain at least one incorrect piece of information.
Step 2
Calculate the percentage by mass of chlorine in phosphorus oxychloride.
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Answer
First, calculate the formula mass of POCl₃:
Formula mass POCl₃=31.0+(16.0×3)+(35.5×1)=153.5
Next, calculate the percentage by mass of chlorine:
%Cl=153.535.5×100=23.1%
Step 3
Show, using a calculation, which reaction, A or B, is taking place.
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Answer
To identify the correct reaction, we first calculate the number of moles of iron and the molar mass of iron chloride:
Molar mass of FeCl₃ = 55.8 + (35.5 \times 3) = 162.3 g/mol.
Number of moles of Fe = \frac{8.40}{55.8} = 0.150 moles.
From reaction A (1:1:3 stoichiometry):
Moles of FeCl₃ formed from 0.150 moles of Fe = 0.150 moles.
Mass of FeCl₃ produced = 0.150 \times 162.3 = 24.35 g.
From reaction B (2:3 stoichiometry):
Moles of FeCl₃ produced = 0.075 moles.
Mass of FeCl₃ produced = 0.075 \times 162.3 = 12.18 g.
Since 19.05g of FeCl₃ was produced, the reaction taking place is reaction A.
