Chapter 20, Problem 23PS

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074

Chapter
Section

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074
Textbook Problem

# Energy consumption in the United States amounts to the equivalent of the energy obtained by burning 7.0 gal of oil or 70. lb of coal per day per person. Using data in Table 20.4, carry out calculations to show that the energy evolved from these quantities of oil and coal is approximately equivalent. The density of fuel oil is approximately 0.8 g/mL.(1.00 gal = 3.785 L and 1.00 lb = 454 g)

Interpretation Introduction

Interpretation:

The energy evolved from the same quantity of coal and oil is approximately equivalent should be proved.

Concept introduction:

• Enthalpy of combustion is the energy released by a combustion reaction between hydrocarbons, oxygen and heat source.
• Enthalpy of formation is the heat released or absorbed in a chemical reaction at constant temperature when simple substances combine into a more complex substance.
• 1lb=453.6g
• 1.0gal=3.785L
Explanation

Given,

The enthalpy of combustion of coal is 33â€‰KJ/g .

Per capita energy consumption in the United States has been equated to the energy obtained by burning 70â€‰â€‰lb of coal per day.

The lb unit (pound) can be converted into gram by multiplying the given value with 453.6â€‰g/lb.

Then the energy released as heat in kilojoules, when 70â€‰â€‰lb of coal is burned can be calculated as follows,

â€‚Â 70.0â€‰lbâ€‰Ã—â€‰(453.6â€‰g/lb)Ã—(33â€‰kJ/g)â€‰â€‰=â€‰â€‰1.0â€‰Ã—â€‰106â€‰kJ

Similarly the energy evolved from 7.0â€‰â€‰â€‰galâ€‰â€‰ofâ€‰â€‰oil on combustion can be determined as follows,

The enthalpy of combustion of oil is 43â€‰kJ/g

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