Gce Model Questions Vol1 2021 Chemistry Question 6

Practice essay / theory question 6 from the 2021 Gce Model Questions Vol1 Chemistry examination. This question covers States of Matter, Phase changes, Specific heat capacity, Heat of vaporisation, Energy calculations .

Gce Model Questions Vol1 2021 Chemistry Essay / Theory
Topics: States of Matter Phase changes Specific heat capacity Heat of vaporisation Energy calculations
Question 6 GCE_MODEL_QUESTIONS_VOL1 • 2021 • CHEMISTRY • essay

A 12.0 g sample of a pure liquid substance (molar mass = 84.0 g mol⁻¹) is initially at 20.0 °C. The substance has a specific heat capacity of 2.0 J g⁻¹ K⁻¹ in the liquid state and a heat of vaporisation of 35.0 kJ mol⁻¹ at its normal boiling point of 150.0 °C. The surrounding atmosphere is at 1 atm pressure. The sample is placed in an insulated calorimeter and 1.20 MJ of heat is supplied uniformly.\n\nAnswer the following:

Question Parts

( a )
Calculate the amount of heat required to raise the temperature of the liquid from 20.0 °C to its boiling point (150.0 °C).
( b )
From the remaining heat after reaching the boiling point, determine the mass of the liquid that will be completely vaporised.
( c )
If after vaporising the mass found in part (b) there is still heat left, calculate the final temperature of the vapour assuming no further phase change occurs. (Use the specific heat capacity of the vapour as 1.5 J g⁻¹ K⁻¹.)
( d )
Briefly discuss why the boiling point of the substance would change if the external pressure were reduced to 0.5 atm.

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About This Question

This is Gce Model Questions Vol1 2021 Chemistry Question 6. It is one of the essay questions from the 2021 Gce Model Questions Vol1 Chemistry examination.

The question covers States of Matter, Phase changes, Specific heat capacity, Heat of vaporisation, Energy calculations .

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