Chemistry MCQ Practice

The table shows the boiling points of some gases in air.

 

Gas	Boiling Point/ °C
Argon	-186
Helium	-269
Neon	-246
Nitrogen	-196
Oxygen	-183

 

When air is cooled to -200 °C, which gases will liquefy?

 

A)  argon, helium, neon

 

B)  argon, nitrogen, oxygen

 

C)  helium, neon, nitrogen

 

D)  helium, neon

 

 

Answer: B

 

- For such questions, drawing a number line can be very useful i.e.

 

(1) draw a line to represent temperature range (left to right = increasing temperature),
(2) mark out 2 points and indicate melting point and boiling point,
(3) write the states (solid, liquid, gas) in the corresponding regions.

 

 

- Next, mark out the temperature(s) given in the question.

 

 

- As shown in the diagram above, for a gas to be liquid at -200 °C, the boiling point must be higher than -200 °C.
- Do take note that since the temperatures are negative, the larger the numerical value, the lower is the temperature.