Neco 2021 Chemistry Question 32

Practice objective / multiple choice question 32 from the 2021 Neco Chemistry examination.

Neco 2021 Chemistry Objective / Multiple Choice Medium Difficulty
Question 32 NECO • 2021 • CHEMISTRY • objective

A pure substance has a triple point at a pressure of 0.5\,MPa and a temperature of 250\,K. Its enthalpy of fusion is \(6.0\ \text{kJ mol}^{-1}\) and the molar volume change on melting is \(1.2\times10^{-6}\ \text{m}^3\text{mol}^{-1}\). (a) Using the Clapeyron equation, estimate the slope \(\frac{dP}{dT}\) of the solid-liquid equilibrium line near the triple point. (b) Assuming the liquid-vapor equilibrium follows the Clausius-Clapeyron relation with \(\Delta H_{\text{vap}} = 30\ \text{kJ mol}^{-1}\) and that the vapor pressure at the triple point equals the triple‑point pressure, calculate the vapor pressure at 300\,K.

Answer Options

A. dP\/dT ≈ 2.5×10⁷ Pa K⁻¹ (25 MPa K⁻¹); vapor pressure at 300 K ≈ 7.0 MPa
B. dP\/dT ≈ 1.8×10⁷ Pa K⁻¹ (18 MPa K⁻¹); vapor pressure at 300 K ≈ 4.2 MPa
C. dP\/dT ≈ 1.0×10⁷ Pa K⁻¹ (10 MPa K⁻¹); vapor pressure at 300 K ≈ 3.0 MPa
Correct Answer D. dP/dT ≈ 2.0×10⁷ Pa K⁻¹ (20 MPa K⁻¹); vapor pressure at 300 K ≈ 5.5 MPa
Correct Answer
D
Correct Option:
dP/dT ≈ 2.0×10⁷ Pa K⁻¹ (20 MPa K⁻¹); vapor pressure at 300 K ≈ 5.5 MPa

About This Question

This is Neco 2021 Chemistry Question 32. It is one of the objective questions from the 2021 Neco Chemistry examination.

Difficulty level: Medium .

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