   Chapter 5, Problem 24PS

Chapter
Section
Textbook Problem

A 25.0-mL sample of benzene at 19.9 °C was cooled to its melting point, 5.5 °C, and then frozen How much energy was given off as heat in this process? (The density of benzene is 0.80 g/mL, its specific heat capacity is 1.74 J/g · K, and its heat of fusion is 127 J/g.)

Interpretation Introduction

Interpretation:

The amount of released in the process has to be calculated.

Concept Introduction:

Heat energy required to raise the temperature of 1g of substance by 1k.Energy gained or lost can be calculated using the below equation.

q=C×m×ΔT

Where,

q= energy gained or lost for a given mass of substance (m),

C =specific heat capacity

ΔT= change in temperature

Explanation

Given,

Density of benzene=0.80g/mL

Mass of benzene = Density × volume

Substitute in the given equation as

Mass of benzene=0.80g/mL×25mL =20g

Melting point=5.50C

Heat of fusion of benzene=127J/g

To decrease the temperature of 19.90C-5.50C

q=C×m×ΔT

Substitute in the above equation as

q1 =1

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