Neco 2017 Chemistry Question 6

Practice essay / theory question 6 from the 2017 Neco Chemistry examination. This question covers States of Matter, Phase diagrams, Clausius–Clapeyron equation, Enthalpy of vaporisation .

Neco 2017 Chemistry Essay / Theory

Topics: States of Matter Phase diagrams Clausius–Clapeyron equation Enthalpy of vaporisation

Question 6 NECO • 2017 • CHEMISTRY • essay

The phase diagram of a pure substance X shows that its normal boiling point (1 atm) is 350 K. Two vapor‑pressure measurements are recorded: - At 300 K, the vapour pressure is 0.10 atm. - At 320 K, the vapour pressure is 0.30 atm. Assume the enthalpy of vaporisation (ΔHvap) is constant over this temperature range. Answer the following:

Question Parts

( a )

Explain, using the phase diagram, how pressure and boiling point are related for substance X.

( b )

Calculate the enthalpy of vaporisation (ΔHvap) of X in kJ mol⁻¹ using the two given vapour‑pressure data points.

( c )

Using the ΔHvap obtained in part (b), estimate the boiling point of X when the external pressure is 0.50 atm. Give your answer to the nearest kelvin.

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About This Question

This is Neco 2017 Chemistry Question 6. It is one of the essay questions from the 2017 Neco Chemistry examination.

The question covers States of Matter, Phase diagrams, Clausius–Clapeyron equation, Enthalpy of vaporisation .

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