Reactions of acids and saltsIB MYP Sciences: Subtopic test

1. 1
   A student in Cairo adds a piece of magnesium ribbon to dilute sulfuric acid in a test tube. The mixture fizzes and the test tube becomes warm. When the student holds a lit splint at the mouth of the tube, it goes out with a squeaky pop.

   (a)

   Which gas is produced in this reaction?

   [1 mark]

   • ACarbon dioxide
   • BHydrogen
   • COxygen
   • DSteam

   (b)

   What is the name of the salt formed in this reaction?

   [1 mark]

   • AMagnesium sulfate
   • BMagnesium chloride
   • CMagnesium nitrate
   • DMagnesium sulfide

   (c)

   Write a word equation for the reaction between magnesium and dilute sulfuric acid.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student in Seoul adds small chips of marble (calcium carbonate) to dilute hydrochloric acid in a conical flask on a balance. The mixture fizzes and the reading on the balance slowly falls. The gas given off is collected and tested.

   (a)

   Which result of a test shows that the gas is carbon dioxide?

   [1 mark]

   • AIt relights a glowing splint
   • BIt burns with a squeaky pop
   • CIt bleaches damp litmus paper
   • DIt turns limewater milky (cloudy)

   (b)

   What is the name of the salt formed in this reaction?

   [1 mark]

   • ACalcium oxide
   • BCalcium sulfate
   • CCalcium chloride
   • DCalcium nitrate

   (c)

   Explain why the reading on the balance slowly falls during the reaction.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Kofi, a student in Accra, makes copper(II) sulfate crystals. He warms 25 cm³ of dilute sulfuric acid, adds copper(II) oxide a spatula at a time while stirring, and keeps adding until some black solid remains undissolved. The solution turns blue. He filters the mixture, then heats the filtrate in an evaporating basin until all the water has gone. He obtains a small amount of pale blue powder instead of the large blue crystals he expected.

   (a)

   Write a word equation for the reaction, and explain why Kofi adds copper(II) oxide until some remains undissolved.

   [3 marks]

   (b)

   Evaluate Kofi's method and suggest two improvements so that he obtains large, pure crystals.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A hotel in Dubai uses a descaling liquid containing dilute hydrochloric acid to remove limescale, which is mainly calcium carbonate, from its kettles. Staff notice that the liquid fizzes on the limescale, and also fizzes slowly if it splashes onto the zinc-coated metal sink. The manager is deciding whether to keep using this product or to switch to a milder one.

   (a)

   Explain the fizzing on the limescale and on the zinc-coated sink. Include word equations and describe a chemical test for each gas.

   [6 marks]

   (b)

   Discuss and evaluate whether the hotel should continue to use the hydrochloric acid descaler.

   [6 marks]

   Total for question 4: 12 marks

End of questions