1. 1
   An engineer at an ammonia production plant is monitoring a side reaction that releases a gaseous by-product. She measures the volume of the gas collected at room temperature and pressure (RTP) and wants to work out how many moles of gas this represents, so that she can check the plant is operating safely and efficiently.

   (a)

   She wants to convert the volume of gas collected into an amount in moles. Which value should she use as the molar volume of any gas at RTP?

   [1 mark]

   • A1 dm3
   • B22 dm3
   • C24 dm3
   • D100 dm3

   (b)

   The engineer records the temperature and pressure conditions in the plant control room before taking her gas volume reading. Which conditions correspond to room temperature and pressure (RTP), as used when applying the molar gas volume of 24 dm3?

   [1 mark]

   • A0 degrees Celsius and 2 atmospheres
   • B20 degrees Celsius and 1 atmosphere
   • C100 degrees Celsius and 1 atmosphere
   • D20 degrees Celsius and 2 atmospheres

   (c)

   The engineer collects 6 dm3 of the gaseous by-product at RTP. Calculate the number of moles of gas she has collected.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A quality control chemist at a fizzy drinks factory reacts a sample of sodium hydrogencarbonate with excess acid to test how much carbon dioxide gas a batch will release, so that the correct amount of fizz can be added to each drink.

   (a)

   Which equation correctly links the amount of gas in moles to its volume at RTP?

   [1 mark]

   • Amoles = volume in dm3 divided by 24
   • Bmoles = volume in dm3 multiplied by 24
   • Cmoles = 24 divided by volume in dm3
   • Dmoles = volume in cm3 divided by 24

   (b)

   The chemist needs to know the number of moles of carbon dioxide (CO2) released from a known mass of gas. Which formula should she use to convert a mass of gas into an amount in moles?

   [1 mark]

   • Amoles = mass multiplied by relative formula mass
   • Bmoles = mass divided by 24
   • Cmoles = relative formula mass divided by mass
   • Dmoles = mass divided by relative formula mass

   (c)

   The chemist finds that a reaction produces 0.1 mol of carbon dioxide gas. Calculate the volume, in dm3, that this gas occupies at RTP.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   In an early 19th century experiment, a chemist reacted a 5 g sample of marble (calcium carbonate, CaCO3) with an excess of dilute hydrochloric acid, according to the equation CaCO3 + 2HCl -> CaCl2 + H2O + CO2. He wanted to measure the volume of carbon dioxide gas released in order to test his ideas about the composition of gases.

   (a)

   Given a relative formula mass of 100 for CaCO3, calculate the number of moles of calcium carbonate in the 5 g sample.

   [3 marks]

   (b)

   Using the equation CaCO3 + 2HCl -> CaCl2 + H2O + CO2 and your answer to part (a), calculate the volume of carbon dioxide gas produced at RTP.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A team of engineers is designing a weather balloon that must be filled with 2400 dm3 of hydrogen gas at RTP. They plan to generate the hydrogen by reacting zinc with excess dilute sulfuric acid, according to the equation Zn + H2SO4 -> ZnSO4 + H2. The relative atomic mass of zinc is 65.

   (a)

   Calculate the minimum mass of zinc the engineers must use to generate this volume of hydrogen gas, showing each step of your working clearly.

   [6 marks]

   (b)

   When the engineers carry out the reaction in practice, the actual volume of hydrogen collected is less than the calculated value from part (a). Evaluate two possible reasons for this difference, and discuss two further practical factors the engineers must consider when scaling up this reaction to fill a large weather balloon safely.

   [6 marks]

   Total for question 4: 12 marks

End of questions