Electrochemical cellsIB MYP Chemistry: Subtopic test

1. 1
   A student makes a simple cell by placing a strip of zinc and a strip of copper in a beaker of sodium chloride solution, and joins the two strips to a voltmeter with wires. The voltmeter shows a reading of about 1 V.

   (a)

   Which metal is the negative terminal of the cell, and why?

   [1 mark]

   • ACopper, because it is more reactive
   • BCopper, because it is less reactive
   • CZinc, because it is less reactive
   • DZinc, because it is more reactive and loses electrons more easily

   (b)

   In which direction do the electrons flow?

   [1 mark]

   • AThrough the solution from copper to zinc
   • BThrough the wires from zinc to copper
   • CThrough the wires from copper to zinc
   • DThrough the solution from zinc to copper

   (c)

   State the purpose of the sodium chloride solution in the cell.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student makes simple cells by connecting a copper strip and a strip of a second metal to a voltmeter, with both strips dipped in the same salt solution. The second metal was magnesium in the first cell, zinc in the second and iron in the third. The readings were 2.0 V, 1.1 V and 0.7 V respectively. In every cell the second metal was the negative terminal.

   (a)

   Which statement correctly explains why the magnesium cell gave the highest voltage?

   [1 mark]

   • AMagnesium is furthest from copper in reactivity, so the difference in reactivity is greatest
   • BMagnesium is the least reactive of the three second metals
   • CMagnesium is the closest in reactivity to copper
   • DMagnesium is the only metal that conducts electricity

   (b)

   Silver is less reactive than copper. A cell is made from a copper strip and a silver strip in the same solution. Which prediction is correct?

   [1 mark]

   • ASilver is the negative terminal and the voltage is above 2.0 V
   • BElectrons flow from silver to copper
   • CCopper is the negative terminal and electrons flow from copper to silver
   • DThere is no voltage because both metals are unreactive

   (c)

   Describe the pattern in the results.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A car manufacturer in Seoul has developed a car powered by a hydrogen-oxygen fuel cell. Hydrogen from a pressurised tank and oxygen from the air are fed into the fuel cell, which produces the electricity that drives the motor. The only substance leaving the exhaust is water.

   (a)

   Outline how a hydrogen-oxygen fuel cell produces electricity.

   [3 marks]

   (b)

   Explain why the car does not need recharging but must be refuelled, and give one environmental advantage and one environmental disadvantage of using hydrogen fuel cells.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Pupils at a rural school in Kenya use torches powered by disposable zinc batteries. A charity proposes replacing these with rechargeable batteries that are charged by small solar panels. The science teacher wants her class to understand how a simple cell works before they decide.

   (a)

   Explain how a simple cell made from a zinc strip and a copper strip in an electrolyte produces a voltage, and why the cell eventually stops working.

   [6 marks]

   (b)

   Evaluate the charity's proposal to replace disposable batteries with rechargeable batteries charged by solar panels.

   [6 marks]

   Total for question 4: 12 marks

End of questions