Acid Rain

Recommended for grades 9–12.

Figure from experiment 25 from Science with TI-Nspire Technology

Introduction

In this experiment, you will observe the formation of four acids that occur in acid rain:

carbonic acid, H₂CO₃
nitrous acid, HNO₂
nitric acid, HNO₃
sulfurous acid, H₂SO₃

Carbonic acid occurs when carbon dioxide gas dissolves in rain droplets of unpolluted air:

${\text{C}}{{\text{O}}_{\text{2}}}{\text{(g) + }}{{\text{H}}_{\text{2}}}{\text{O(1)}} \to {{\text{H}}_{\text{2}}}{\text{C}}{{\text{O}}_{\text{3}}}{\text{(aq)}}$

Nitrous acid and nitric acid result from a common air pollutant, nitrogen dioxide (NO₂). Most nitrogen dioxide in our atmosphere is produced from automobile exhaust. Nitrogen dioxide gas dissolves in rain drops and forms nitrous and nitric acid:

${\text{2 N}}{{\text{O}}_{\text{2}}}{\text{(g) + }}{{\text{H}}_{\text{2}}}{\text{O(1)}} \to {\text{HN}}{{\text{O}}_{\text{2}}}{\text{(aq) + HN}}{{\text{O}}_{\text{3}}}{\text{(aq)}}$

Sulfurous acid is produced from another air pollutant, sulfur dioxide (SO₂). Most sulfur dioxide gas in the atmosphere results from burning coal containing sulfur impurities. Sulfur dioxide dissolves in rain drops and forms sulfurous acid:

${\text{S}}{{\text{O}}_{\text{2}}}{\text{(g) + }}{{\text{H}}_{\text{2}}}{\text{O(1)}} \to {{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{3}}}{\text{(aq)}}$

Objectives

In this experiment, you will

Generate three gaseous oxides, CO₂, SO₂, and NO₂.
Simulate the formation of acid rain by bubbling each of the three gases into water and producing three acidic solutions.
Measure the pH of the three resulting acidic solutions to compare their relative strengths.

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

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