Factors affecting rateIB MYP Chemistry: Subtopic test

1. 1
   A student in Lima reacts 1.0 g of zinc granules with 50 cm³ of excess dilute hydrochloric acid and measures the volume of hydrogen made over time. She then repeats the experiment with 1.0 g of zinc powder, keeping everything else the same.

   (a)

   Which factor is the independent variable in this comparison?

   [1 mark]

   • AThe surface area of the zinc
   • BThe mass of zinc
   • CThe volume of the acid
   • DThe volume of hydrogen made

   (b)

   How does the volume of hydrogen against time line for the powder compare with the line for the granules?

   [1 mark]

   • ASteeper at the start and a higher final volume
   • BLess steep at the start and the same final volume
   • CThe same steepness and a higher final volume
   • DSteeper at the start and the same final volume

   (c)

   Explain why zinc powder reacts faster than zinc granules.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Ammonia for fertiliser is made in the Haber process, in which nitrogen gas reacts with hydrogen gas at high temperature and high pressure in the presence of an iron catalyst. Engineers at the plant are always looking for ways to make ammonia faster.

   (a)

   Which statement about the iron catalyst is correct?

   [1 mark]

   • AIt is used up and must be replaced after each reaction
   • BIt slows down the reaction
   • CIt speeds up the reaction and is not used up
   • DIt makes the reaction release more energy

   (b)

   Why does increasing the pressure of the nitrogen and hydrogen increase the rate of reaction?

   [1 mark]

   • AThe gas particles move more slowly
   • BThe gas particles are closer together, so they collide more often
   • CThe gas particles become smaller
   • DThe gas particles are heated up

   (c)

   State two ways, other than adding a catalyst, of increasing the rate of the reaction between nitrogen and hydrogen.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An engineer in Seoul tests an effervescent tablet that fizzes when it is dropped into 200 cm³ of water. She times how long the tablet takes to stop fizzing at three temperatures. At 15 °C it takes 120 s, at 25 °C it takes 60 s and at 35 °C it takes 30 s.

   (a)

   Describe the effect of temperature on the rate of reaction, using the data to support your answer.

   [3 marks]

   (b)

   Explain, in terms of particles, why increasing the temperature increases the rate of reaction.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A chemical company in Rotterdam makes hydrogen peroxide solution for hospitals and water-treatment plants. Hydrogen peroxide slowly decomposes into water and oxygen. The decomposition is sped up by manganese(IV) oxide, which is a catalyst. Company chemists are investigating the factors that affect the rate, and the managers are also considering using catalysts in other production processes.

   (a)

   Plan an investigation into how the concentration of hydrogen peroxide affects the rate at which oxygen is made when manganese(IV) oxide is added. Include a testable hypothesis, the variables and a precaution.

   [6 marks]

   (b)

   Discuss the benefits and drawbacks of the company using catalysts in its production processes and evaluate whether it should do so.

   [6 marks]

   Total for question 4: 12 marks

End of questions