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Heat of Combustion: Magnesium

Figure from experiment 19 from Chemistry with Vernier

Introduction

In Experiment 18, you learned about the additivity of reaction heats as you confirmed Hess’s law. In this experiment, you will use this principle as you determine a heat of reaction that would be difficult to obtain by direct measurement—the heat of combustion of magnesium ribbon. The reaction is represented by the equation

{\text{(4)  Mg(s)  +  1/2 }}{{\text{O}}_{\text{2}}}{\text{(g)}} \to {\text{MgO(s)}}

This equation can be obtained by combining equations (1), (2), and (3):

{\text{(1)  MgO(s)  +  2 HCl(aq)}} \to {\text{MgC}}{{\text{l}}_{\text{2}}}{\text{(aq)  +  }}{{\text{H}}_{\text{2}}}{\text{O(1)}} {\text{(2)  Mg(s)  +  2 HCl(aq)}} \to {\text{MgC}}{{\text{l}}_{\text{2}}}{\text{(aq)  +  }}{{\text{H}}_{\text{2}}}{\text{(g)}} {\text{(3)  }}{{\text{H}}_{\text{2}}}{\text{(g)  +  1/2 }}{{\text{O}}_{\text{2}}}{\text{(g)}} \to {{\text{H}}_{\text{2}}}{\text{O(1)}}

The pre-lab portion of this experiment requires you to combine equations (1), (2), and (3) to obtain equation (4) before you do the experiment. Heats of reaction for equations (1) and (2) will be determined in this experiment. As you may already know, ΔH for reaction (3) is –285.8 kJ.

Objectives

In this experiment, you will

  • Combine three chemical equations to obtain a fourth.
  • Use prior knowledge about the additivity of reaction heats.
  • Determine the heat of combustion of magnesium ribbon.

Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

Option 1

Option 2

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Standards Correlations

See all standards correlations for Chemistry with Vernier »

Experiment 19 from Chemistry with Vernier Lab Book

<em>Chemistry with Vernier</em> book cover

Included in the Lab Book

Vernier lab books include word-processing files of the student instructions, essential teacher information, suggested answers, sample data and graphs, and more.

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