Ch.11 - Liquids, Solids & Intermolecular ForcesWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Problem

Consider the heating curve shown below for 22.86 grams of an unknown substance. You may assume constant pressure conditions. Note: the points are labeled as (amount of heat added, temperature). 

Calculate the enthalpy of fusion, ΔH fus, (in kJ/mol). Show all work and circle your final answer. The moles were identified to be 0.496 mol.

Solution

We are asked to the enthalpy of fusion, ΔH fus, (in kJ/mol) given the heating curve. 

Phase changes occur on the horizontal parts of the curve since there are no temperature changes. 


We go through the following steps to solve this problem:

Step 1. Calculate the heat to vaporize

Step 2. Calculate the molar heat of fusion


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