Neutralisation and making saltsIB MYP Chemistry: Subtopic test

1. 1
   A school technician in Dubai prepares blue crystals of copper(II) sulfate for a Year 9 class. She warms 50 cm³ of dilute sulfuric acid and adds black copper(II) oxide a spatula at a time, stirring, until some black solid remains at the bottom of the beaker. She then filters the mixture and heats the blue filtrate in an evaporating basin until crystals begin to form at the edge.

   (a)

   Which row correctly gives the products of the reaction between sulfuric acid and copper(II) oxide?

   [1 mark]

   • ACopper(II) sulfate and water
   • BCopper(II) sulfate and hydrogen
   • CCopper(II) sulfate, water and carbon dioxide
   • DCopper(II) chloride and water

   (b)

   Why does the technician keep adding copper(II) oxide until some solid remains?

   [1 mark]

   • ATo make the solution more acidic
   • BTo make sure all the acid has reacted
   • CTo produce more water in the beaker
   • DTo make the copper(II) oxide dissolve

   (c)

   Explain why the mixture must be filtered before the filtrate is heated.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student in Nairobi investigates how the mass of calcium carbonate affects the volume of carbon dioxide made. Each time, she adds a different mass of calcium carbonate chips to 50 cm³ of 1.0 mol dm⁻³ hydrochloric acid in a flask connected to a gas syringe, and records the total volume of gas collected once the fizzing stops. Masses of 0.5 g, 1.0 g, 1.5 g, 2.0 g, 3.0 g and 4.0 g give volumes of 120 cm³, 240 cm³, 360 cm³, 480 cm³, 600 cm³ and 600 cm³ respectively.

   (a)

   Which variable is the dependent variable in this investigation?

   [1 mark]

   • AThe mass of calcium carbonate
   • BThe volume of hydrochloric acid
   • CThe volume of carbon dioxide collected
   • DThe concentration of the acid

   (b)

   Which test confirms that the gas collected in the syringe is carbon dioxide?

   [1 mark]

   • AIt relights a glowing splint
   • BIt makes a lit splint burn with a squeaky pop
   • CIt bleaches damp litmus paper
   • DIt turns limewater cloudy

   (c)

   Describe the trend in the results for masses of calcium carbonate from 0.5 g to 2.0 g.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student in Singapore wants to find out how much 0.100 mol dm⁻³ hydrochloric acid is needed to neutralise 25.0 cm³ of sodium hydroxide solution. She uses a pipette, a burette, a conical flask and phenolphthalein indicator, which is pink in alkali and colourless in acid. She repeats the titration several times. Her titres are 24.8 cm³, 24.3 cm³, 24.4 cm³ and 24.5 cm³.

   (a)

   Describe how the student should carry out the first titration, from filling the burette to finding the titre.

   [3 marks]

   (b)

   Process the results to find the mean titre. Concordant results agree to within 0.2 cm³. Explain which results you use.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A fertiliser company in Gujarat, India makes ammonium nitrate by reacting nitric acid with ammonia solution. The salt is crystallised and sold to farmers, whose crop yields rise when it is added to the soil. Rain can wash unused fertiliser into nearby rivers, where it makes algae grow rapidly and use up the oxygen in the water.

   (a)

   Discuss the benefits and drawbacks of using ammonium nitrate fertiliser, and reach a justified conclusion.

   [6 marks]

   (b)

   In the laboratory, ammonium nitrate is made from nitric acid and ammonia solution, which are both soluble. Explain why a student cannot add an excess of one reactant and filter it off, and describe a method to make pure, dry crystals of ammonium nitrate.

   [6 marks]

   Total for question 4: 12 marks

End of questions