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A student carried out an investigation to determine the order of reactivity of four metals, W, X, Y, and Z - Edexcel - GCSE Chemistry - Question 9 - 2022 - Paper 1
Question 9
A student carried out an investigation to determine the order of reactivity of four metals, W, X, Y, and Z. A piece of metal W was added to a test tube containing e... show full transcript
Worked Solution & Example Answer:A student carried out an investigation to determine the order of reactivity of four metals, W, X, Y, and Z - Edexcel - GCSE Chemistry - Question 9 - 2022 - Paper 1
Step 1
Use the information in Figure 8 to place the metals in order of reactivity from the least reactive to the most reactive.
Answer
The order of reactivity from least to most reactive is:
X - Y - W - Z
This is deduced from the observations where metal X showed very little reaction, metal Y reacted quickly, metal W reacted quickly with some remaining metal after three minutes, and metal Z completed the reaction fully.
Step 2
Explain why the reaction between metal Y and excess dilute sulfuric acid stopped even though there was solid metal Y left.
Answer
The reaction between metal Y and dilute sulfuric acid stopped because the metal Y likely formed a protective layer of sulfate or similar compound on its surface, which prevented further reaction with the acid. This passivation occurs when the surface of the metal becomes coated, stopping additional oxidation and hydrogen gas production.
Step 3
Explain the meaning of the term weak acid.
Answer
A weak acid is one that does not completely dissociate into ions in solution. In contrast to strong acids, which fully ionize and release protons (H⁺) into the solution, weak acids only partially dissociate, resulting in a lower concentration of hydrogen ions. This means weak acids are less effective at donating protons and thus have a smaller effect on the pH of solutions.
Step 4
Calculate the total number of atoms that combine to form 5.13 g of aluminum sulfate.
Answer
First, determine the formula mass of Al₂(SO₄)₃:
- Al: 2 x 27.0 = 54.0
- S: 3 x 32.0 = 96.0
- O: 12 x 16.0 = 192.0 Total formula mass = 54.0 + 96.0 + 192.0 = 342.0 g/mol
Next, find the number of moles in 5.13 g of Al₂(SO₄)₃: Moles = mass / molar mass = 5.13 g / 342.0 g/mol = 0.0150 mol
The total number of atoms in Al₂(SO₄)₃:
- Each formula unit has 2 Al, 3 S, and 12 O atoms, giving a total of 17 atoms per formula unit.
Total number of atoms = 0.0150 mol x 17 atoms/formula unit x 6.02 x 10²³ atoms/mol = 1.53 x 10²² atoms.
Step 5
Carry out a calculation, using the information above, to show which equation represents the reaction taking place.
Answer
From the data given: 4.48 g of iron = 4.48 g / 56.0 g/mol = 0.0800 mol of Fe. According to the equations:
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For Equation 1: 1 mol of Fe reacts with 1 mol of Pb, hence 0.0800 mol of Fe should produce 0.0800 mol of Pb. Total mass of Pb produced = 0.0800 mol x 207 g/mol = 16.56 g.
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For Equation 2: 2 mol of Fe produces 3 mol of Pb. Thus, 0.0800 mol of Fe will produce (3/2) * 0.0800 mol = 0.1200 mol of Pb. Total mass of Pb produced = 0.1200 mol x 207 g/mol = 24.84 g.
Thus, Equation 2 represents the reaction taking place.