Neco Model Questions Vol1 2022 Chemistry Question 4

In a laboratory experiment a clean, dry piece of magnesium ribbon was weighed and then reacted with excess hydrochloric acid. The hydrogen gas produced was collected over water. Data recorded: - Mass of magnesium before reaction: 0.150 g - Volume of gas collected: 155.0 mL - Temperature of the gas: 25 °C (298 K) - Atmospheric pressure: 760 mm Hg - Vapour pressure of water at 25 °C: 23.8 mm Hg The reaction is: Mg(s) + 2 HCl(aq) → MgCl₂(aq) + H₂(g) Using the data above, answer the following: (a) Calculate the number of moles of hydrogen gas collected. (b) Determine the experimental molar mass of magnesium from the data. (c) Calculate the percentage error of the experimental molar mass relative to the accepted value of 24.31 g mol⁻¹. (d) Identify two possible sources of error in the experiment and suggest how each could be minimised.