2019 P1 Q6 - Compare Pressure of Gaseous Compounds


In this video we want to discuss 2019 A Level H2 Chemistry Paper 1 Question 6.

2019 p1 q6 question

To determine the relationship between pressure and gaseous compounds of various molar masses, we need to use the Ideal Gas Equation.

From the ideal gas equation PV = nRT, we can write moles(n) as mass(m) / molar mass(M).

Given mass, temperature(T) and volume(V) are all constant, we can combine these terms together with Gas Constant(R) to form a big constant term.

This will give us the relationship between pressure(P) and molar mass.

2019 p1 q6 relationship between pressure and molar mass

Hence we can deduce pressure is inversely proportionate to molar mass.

This means the smaller the molar mass of the compound, the higher the pressure.

We can now look back at the list of compounds given to work out their molar masses.

2019 p1 q6 deduce pressure trend

CH4 with the smallest molar mass will have the highest pressure, while CH3Cl with the biggest molar mass will have the lowest pressure.

Finally we can look back at the options and choose the graph where CH4 has the highest pressure and CH3Cl has the lowest pressure.

2019 p1 q6 deduce answer

Hence the answer to this question is A.

Topic: Gaseous State, Physical Chemistry, A Level Chemistry, Singapore

Back to list of questions for 2019 A Level H2 Chemistry Paper 1

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