Acid Rain

Recommended for grades 6–12.

Figure from experiment 29 from Physical Science with Vernier

Introduction

Acid rain is a topic of much concern in today’s world. As carbon dioxide gas, CO₂, dissolves in water droplets of unpolluted air, the following reaction happens

${\text{C}}{{\text{O}}_{\text{2}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}} \to {{\text{H}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}$

H₂CO₃ is a weak acid that causes the rain from unpolluted air to be slightly acidic.

Oxides of sulfur dissolve in water droplets to cause more serious problems. Sulfur trioxide dissolves to produce sulfuric acid, H₂SO₄, by the equation

${\text{S}}{{\text{O}}_{\text{3}}}{\text{ + }}{{\text{H}}_{\text{2}}}{\text{O}} \to {{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$

The acidity of a solution can be expressed using the pH scale, which ranges from 0 to 14. Solutions with pH above 7 are basic, solutions with pH below 7 are acidic, and a neutral solution has a pH of 7. In Part I of this experiment, you will study the effect of dissolving CO₂ in distilled water, which is similar to rain water, on the pH of the water. Then in Part II, you will study the effects of dissolving sulfuric acid on the pH of different water types.

Objectives

In this experiment, you will

Measure pH.
Study the effect of dissolved CO₂ on the pH of distilled water.
Study the effect on pH of dissolving H₂SO₄ in various waters.
Learn why some bodies of water are more vulnerable to acid rain than others.

Sensors and Equipment

This experiment requires each of the following Vernier sensors and equipment (unless otherwise noted):

pH Sensor

Additional Requirements

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

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Step-by-step instructions for computer-based data collection
List of materials and equipment

Note: The experiment preview of the computer edition does not include essential teacher information, safety tips, or sample data. Instructions for Logger Pro and other software (such as LabQuest App or TI handheld software, where available) are on the CD that accompanies the book. We strongly recommend that you purchase the book before performing experiments.

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