Group 0: the noble gasesIB MYP Chemistry: Subtopic test

1. 1
   A party shop in Dubai fills foil balloons with helium. The balloons float upwards when released, and the shop owner has been told that helium is much safer to use than hydrogen.

   (a)

   Which property of helium makes the balloons float upwards?

   [1 mark]

   • AIt is unreactive
   • BIt has a full outer shell of electrons
   • CIt has a high boiling point
   • DIt is less dense than air

   (b)

   How many electrons are in the outer shell of a helium atom?

   [1 mark]

   • A1
   • B2
   • C8
   • D18

   (c)

   Explain why helium is safer than hydrogen for filling balloons.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A welder in a workshop in Seoul joins two stainless steel plates using a very hot electric arc. A steady stream of argon gas is blown over the hot metal while the welding is done.

   (a)

   Which statement about argon atoms is correct?

   [1 mark]

   • AThey have one electron in the outer shell
   • BThey have seven electrons in the outer shell
   • CThey have a full outer shell of eight electrons
   • DThey have outer electrons that are easily lost

   (b)

   How does argon exist as a gas?

   [1 mark]

   • AAs single atoms
   • BAs molecules containing two atoms
   • CAs a giant ionic lattice
   • DAs a giant covalent structure

   (c)

   Explain why argon is used instead of air during welding.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   The boiling points of the first five noble gases are: helium −269 °C, neon −246 °C, argon −186 °C, krypton −153 °C and xenon −108 °C. A student is asked to predict the properties of radon, the next noble gas below xenon. Room temperature is 20 °C.

   (a)

   Describe the trend in boiling point down the group.

   [3 marks]

   (b)

   Use the trend to predict the boiling point of radon and state its physical state at 20 °C.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Helium is a non-renewable gas that is extracted from natural gas fields. Because it is so light, helium that is released escapes into space and is lost. Hospitals need liquid helium, which boils at −269 °C, to cool the magnets in MRI scanners. A government is considering banning helium party balloons to save helium for medical use.

   (a)

   Explain, using electron arrangement and boiling point, why helium is suitable both for balloons and for cooling MRI magnets.

   [6 marks]

   (b)

   Discuss and evaluate whether the government should ban helium party balloons.

   [6 marks]

   Total for question 4: 12 marks

End of questions