Lesson: Enthalpy and Internal Energy Glencoe • Chemistry • Matter & Change • Chemistry • The Molecular Nature of Matter and Change • Eighth Edition • Chemistry 13e • AP Edition

Chemistry

In this lesson, we will learn how to calculate enthalpy changes from changes in internal energy and changes in volume, at constant pressure.

Worksheet

Q1:

A 1.50 mol sample of an ideal gas at 245 K and a pressure of 0.75 bar is altered by some process that takes it to a state in which its temperature is increased to 295 K and its pressure is increased to 0.90 bar. What will the enthalpy change (Δ𝐻) of the gas in this process be?

Q2:

Consider the shown reaction, for which the standard reaction enthalpy has a value of Δ𝐻=−890.4/⦵rkJmol at a temperature of 298 K. 2C()+Cl()+2F()CFClCFCl()sggg2222 What is the value of Δ𝑈⦵r for this reaction at 𝑇=298K?

Q3:

Consider the shown reaction, for which the standard reaction enthalpy is Δ𝐻=−3,228.2/⦵rkJmol. CHCOOH()+O()7CO()+3HO()65222sggl152 Calculate the value of Δ𝑈⦵r for this reaction and determine whether any thermodynamic work is done on (𝑤>0) or by (𝑤<0) the reaction system if the reaction is carried out at a constant pressure. Assume that the gases in this reaction exhibit ideal gas behavior at 𝑇=298.15K and 𝑃=1bar.
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