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This is about silver iodide - AQA - GCSE Chemistry - Question 3 - 2020 - Paper 1
Question 3
This is about silver iodide. Silver iodide is produced in the reaction between silver nitrate solution and sodium iodide solution. The equation for the reaction is... show full transcript
Worked Solution & Example Answer:This is about silver iodide - AQA - GCSE Chemistry - Question 3 - 2020 - Paper 1
Step 1
Explain how the results demonstrate the law of conservation of mass.
Answer
The total mass before the reaction is calculated by adding the masses of beaker A and beaker B. From Table 3, the mass before mixing is:
Total mass before = 78.26 g (Beaker A) + 78.50 g (Beaker B) = 156.76 g.
After mixing, the mass of beaker A and its contents is 108.22 g, and the mass of beaker B and its contents is 48.54 g.
Thus, the total mass after mixing is:
Total mass after = 108.22 g + 48.54 g = 156.76 g.
Since the mass before mixing equals the mass after mixing (156.76 g), it demonstrates that no mass is lost, complying with the law of conservation of mass.
Step 2
Suggest how the student could separate the insoluble silver iodide from the mixture at the end of the reaction.
Answer
The student could use filtration to separate the insoluble silver iodide from the solution. By pouring the mixture through filter paper in a funnel, the solid silver iodide would be retained on the paper, while the liquid surrounding it would pass through.
Step 3
Step 4
Step 5
Calculate the percentage atom economy for the production of silver iodide in this reaction.
Answer
To calculate the percentage atom economy, we first find the total relative formula mass of the reactants:
Total Mr of reactants = Mr of AgNO3 + Mr of NaI = 170 + 150 = 320.
Next, determine the relative formula mass of the desired product:
Mr of AgI = 235.
The formula for percentage atom economy is:
Percentage Atom Economy = (Mass of desired product / Total mass of reactants) × 100
Substituting the values we have:
Percentage Atom Economy = (235 / 320) × 100 = 73.4375%
Rounding to three significant figures, the answer is 73.4%.
Step 6
Give one reason why reactions with a high atom economy are used in industry.
Answer
Reactions with a high atom economy are preferred in industry for sustainable development, as they reduce waste and make more efficient use of resources, leading to a higher yield of useful products with less environmental impact.