S1.5 Ideal gases questions for IB Chemistry
124 questions on Ideal gases, written by Augment in the style of IB exam papers. Six of them are below in full, to answer on paper.
- IB Chemistry
- Part of S1 Models of the particulate nature of matter
- SL and HL
Questions by paper and level
SL and HL questions are for students at either level. HL only questions cover what only HL students study.
| Paper | SL and HL | HL only | All |
|---|---|---|---|
| Paper 1A | 49 | 0 | 49 |
| Paper 1B | 24 | 3 | 27 |
| Paper 2 | 47 | 1 | 48 |
| Every paper | 120 | 4 | 124 |
Counted on
Questions to try
Written by Augment in the style of IB exams, not past papers. Answer them on paper, then check each one against its markscheme with a free account.
Which is an assumption of the ideal gas model?
The molar volume of hydrogen at room conditions was determined. Different masses of magnesium ribbon were each added to excess dilute hydrochloric acid in a conical flask connected to a gas syringe. Room temperature was 21.0 °C and pressure was 101.2 kPa.
Mass of Mg / g ± 0.001 g | 0.020 | 0.030 | 0.040 | 0.050 | 0.060 |
|---|---|---|---|---|---|
Amount of Mg / mmol | 0.823 | 1.234 | 1.645 | 2.057 | 2.468 |
Volume of H2 / cm3 ± 0.5 cm3 | 19.5 | 28.5 | 34.0 | 47.0 | 57.5 |
- line of best fit
- (a)
Write the equation for the reaction, including state symbols.
1 mark
- (b)
Show that the amount of magnesium in 0.050 g is 2.057 mmol.
1 mark
- (c)
Identify the anomalous result and suggest one reason for it.
2 marks
- (d)
Determine the experimental molar volume of hydrogen, in dm3 mol−1, from the gradient of the line of best fit.
2 marks
- (e)
Calculate the theoretical molar volume of an ideal gas, in dm3 mol−1, at the conditions of the experiment. Use section 1 of the data booklet.
1 mark
- (f)
Calculate the percentage error in the experimental value.
1 mark
- (g)
The experimental value is consistently lower than the theoretical value. Suggest one systematic error that would cause this, and a modification to reduce it.
2 marks
A gaseous hydrocarbon, X, contains 85.6 % carbon and 14.4 % hydrogen by mass. A 0.255 g sample of X occupies 150.0 cm3 at 25.0 °C and 100.0 kPa.
- (a)
Determine the empirical formula of X.
2 marks
- (b)(i)
Calculate the molar mass of X, in g mol−1. Use sections 1 and 2 of the data booklet.
3 marks
- (b)(ii)
Deduce the molecular formula of X.
1 mark
- (c)
State one assumption made in using the ideal gas equation in (b)(i).
1 mark
- (d)
The experiment is repeated at a temperature just above the boiling point of X. Explain why the value of the molar mass obtained would be less accurate.
2 marks
Which statements describe an ideal gas?
I. The volume of the particles is negligible compared with the volume of the container.
II. There are no forces of attraction between the particles.
III. The average kinetic energy of the particles is proportional to the temperature in °C.
A column of dry air was trapped in a sealed capillary tube of uniform bore by a short bead of liquid. The tube was placed in a stirred water bath, and the length of the air column, which is proportional to its volume, was measured at different temperatures. The pressure of the trapped air stayed constant.
Temperature / °C ± 0.5 °C | 10.0 | 25.0 | 40.0 | 55.0 | 70.0 | 85.0 |
|---|---|---|---|---|---|---|
Length of air column / cm ± 0.05 cm | 5.67 | 5.95 | 6.27 | 6.55 | 6.88 | 7.15 |
- line of best fit
- (a)
Identify the independent and dependent variables.
1 mark
- (b)
State one variable, other than pressure, that must be kept constant.
1 mark
- (c)
Suggest why the water bath is stirred and left for a few minutes before each length is measured.
1 mark
- (d)
Determine the gradient of the line of best fit, including its units.
2 marks
- (e)
Determine, by extrapolation, the temperature at which the length of the air column would be zero.
2 marks
- (f)
Calculate the percentage error in the value from (e), using the accepted value of −273.15 °C.
1 mark
- (g)
Outline the significance of the temperature found in (e) in terms of the kinetic energy of particles.
2 marks
- (h)
Suggest why the volume of a real sample of air would never actually fall to zero on cooling.
1 mark
Car airbags inflate when solid sodium azide, NaN3, decomposes rapidly to produce nitrogen gas.
An airbag has a volume of 60.0 dm3 when fully inflated. The gas in it is at 125 kPa and 27 °C.
- (a)
Calculate the amount, in mol, of nitrogen in the inflated airbag. Use section 1 of the data booklet.
2 marks
- (b)
Determine the mass, in g, of sodium azide needed.
2 marks
- (c)
Immediately after it inflates, the gas in the bag is at 77 °C. Calculate the pressure of the gas at this temperature, assuming that the volume and amount of gas are the same as in (a).
2 marks
- (d)
Explain why the nitrogen in the airbag can be treated as an ideal gas.
2 marks
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More questions in Models of the particulate nature of matter
- S1.1Introduction to the particulate nature of matter
- S1.2The nuclear atom
- S1.3Electron configurations
- S1.4Counting particles by mass: the mole
- S1.5Ideal gasesThis page
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