IB Chemistry SL S1.5 Ideal gases questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

Type

Multiple choice Written

Difficulty

Easy Medium Hard

Question 1

Multiple choiceMedium1 mark

A fixed amount of an ideal gas is heated from 300 K to 600 K while its pressure increases from 1.0 × 10⁵ Pa to 2.0 × 10⁵ Pa. What happens to its volume and molar volume?

Show answer and explanation

Answer: B. The molar volume is $V/n = RT/P$ Both $T$ and $P$ double, so $T/P$ and the molar volume remain unchanged; with the amount fixed, the volume also remains unchanged.
A: considers the pressure increase but ignores the effect of the doubled temperature.
C: considers the temperature increase but ignores the effect of the doubled pressure.
D: multiplies the temperature and pressure factors instead of using their ratio.
Remember: at fixed amount, volume changes in the same proportion as molar volume.

Question 2

Paper 2Hard12 marks

A laboratory is checking whether the ideal-gas model gives reliable volume estimates for gases in a transfer line. Samples of carbon dioxide and methane are measured at $280\ \mathrm{K}$ The table gives their measured molar volumes and the ideal-gas molar volume at each pressure.

Pressure / bar	Ideal-gas molar volume / dm³ mol⁻¹	Measured CO₂ molar volume / dm³ mol⁻¹	Measured CH₄ molar volume / dm³ mol⁻¹
1.00	23.3	23.1	23.2
5.00	4.66	4.54	4.63
10.0	2.33	2.14	2.29
20.0	1.16	0.94	1.11

(a)

Use Figure 1 to determine the molecular formula of each gas.

[2]

(b)

For an ideal-gas sample of $1.00\ \mathrm{mol}$ at $280\ \mathrm{K}$ and $20.0\ \mathrm{bar}$ calculate the molar volume. Give your answer in $\mathrm{dm^3\,mol^{-1}}$ to three significant figures. Use the ideal gas equation in the data booklet.

[2]

(c)

At $1.00\ \mathrm{bar}$ compare the measured molar volume of each gas with the ideal-gas value.

[2]

(d)

Explain why real gases are more likely to deviate from the ideal-gas model at low temperature and high pressure.

[2]

(e)

A technician argues that the ideal-gas model is equally reliable for carbon dioxide and methane at $280\ \mathrm{K}$ and $20.0\ \mathrm{bar}$ because the ideal molar volume is the same for both gases. Evaluate this argument using the table and Figure 1.

[4]

The best questions are still waiting

Unlock every question in this topic, then type, photograph or draw your answer and have it marked against the markscheme. Find out where you are dropping marks.

Unlock all questions Compare Student and Student Plus