### Introduction

Many chemical reactions give off energy. Chemical reactions that release energy are called exothermic reactions. Some chemical reactions absorb energy and are called endothermic reactions. You will study one exothermic and one endothermic reaction in this experiment.

In Part I, you will study the reaction between citric acid solution and baking soda. An equation for the reaction is:

${{\text{H}}_{\text{3}}}{{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}{{\text{O}}_{\text{7}}}{\text{(aq) + 3 NaHC}}{{\text{O}}_{\text{3}}}{\text{(s)}} \to {\text{3 C}}{{\text{O}}_{\text{2}}}{\text{(g) + 3 }}{{\text{H}}_{\text{2}}}{\text{O(1) + N}}{{\text{a}}_{\text{3}}}{{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}{{\text{O}}_{\text{7}}}{\text{(aq)}}$

In Part II, you will study the reaction between magnesium metal and hydrochloric acid. An equation for this reaction is:

${\text{Mg(s) + 2 HCl(aq)}} \to {{\text{H}}_{\text{2}}}{\text{(g) + MgC}}{{\text{l}}_{\text{2}}}{\text{(aq)}}$

### Objectives

In this experiment, you will

• Study one exothermic and one endothermic reaction.
• Become familiar with using Logger Pro.
• Collect and display data on a graph.