neco 2022 chemistry | Practical

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Question 1 View Details
A student performed an experiment to determine the atomic mass of magnesium using the reaction with dilute hydrochloric acid. The following data were recorded:
Question Parts
(a)
Calculate the number of moles of hydrogen gas collected.
(b)
Using the stoichiometry of the reaction \(\text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2\), calculate the atomic mass of magnesium.
(c)
State two possible sources of error that could affect the result obtained for the atomic mass of magnesium.
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Question 2 View Details
A student is given an unknown aqueous solution of a metal chloride (XCl₂) and carries out the following qualitative tests:
Question Parts
(a)
Identify the metal ion present in the solution based on the observations given.
(b)
Write the symbol, atomic number, group and period of the identified metal in the periodic table.
(c)
Mention two practical applications of this metal.
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Question 3 View Details
A student is given an unknown white crystalline solid that is suspected to be either sodium chloride (NaCl) or potassium chloride (KCl). Using the following experimental procedures, the student must identify the compound and comment on the nature of the bonding present. **Procedures** 1. Perform a flame test on a small amount of the solid. 2. Dissolve a separate portion of the solid in 20 mL of distilled water. 3. Add a few drops of silver nitrate solution (0.1 M AgNO₃) to the aqueous solution and observe any precipitate. 4. Test the conductivity of the aqueous solution with a simple conductivity tester. **Observations recorded by the student** - Flame colour: violet - Solution is clear and colourless. - Immediate formation of a white precipitate on addition of AgNO₃. - The solution conducts electricity strongly.
Question Parts
(a)
Write the balanced chemical equation for the reaction of each possible salt (NaCl and KCl) with silver nitrate.
(b)
Based on the flame‑test observation, state which cation is present in the unknown solid.
(c)
Identify the unknown compound and indicate the type of chemical bond that predominates in it.
(d)
Suggest two possible sources of error in the experiment and explain how each could affect the identification of the salt.
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Question 4 View Details
A student determines the molar mass of an unknown metal by reacting a weighed sample with excess hydrochloric acid and collecting the hydrogen gas released over water. **Data recorded** - Mass of metal sample: 0.250 g - Volume of gas collected (over water): 250.0 mL - Temperature of the gas: 25 °C - Atmospheric pressure: 760 mm Hg - Water‑vapour pressure at 25 °C: 23.8 mm Hg The reaction is assumed to be: \(\text{M} + 2\text{HCl} \rightarrow \text{MCl}_2 + \text{H}_2\) (One mole of metal yields one mole of H₂.) The student is required to calculate the molar mass of the metal and identify it from the list: magnesium (Mg, 24.3 g mol⁻¹), zinc (Zn, 65.4 g mol⁻¹), iron (Fe, 55.8 g mol⁻¹), aluminium (Al, 27.0 g mol⁻¹).
Question Parts
(a)
Calculate the pressure of the dry hydrogen gas collected (in mm Hg).
(b)
Convert the corrected volume of H₂ to moles using the ideal‑gas equation (R = 0.0821 L atm mol⁻¹ K⁻¹).
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