Analyze an environmental problem doing calculations

Sulfur dioxide from a coal plant

Unit 7
10 points
About 24 minutes

You can use a calculator on this question, just like on exam day.

You work through an environmental scenario using numbers: set up and solve calculations (showing your work), then explain the science and propose solutions. Several of the 10 points come from the calculations, usually one for the setup and one for the answer. On the exam: Question 3 of 3 in the 70-minute free-response section (Section II is 40% of the exam score).

The question

A coal-fired power plant burns 2.0 × 10⁶ metric tons of coal per year. The coal contains 2.5% sulfur by mass. When coal burns, each metric ton of sulfur produces 2 metric tons of sulfur dioxide (SO₂). The plant has a scrubber that removes 95% of the SO₂ from its exhaust before the exhaust leaves the smokestack.

Suggested time: 24 minutes

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Part (a)

2 points

Calculate the mass of sulfur, in metric tons, in the coal the plant burns each year. Show your work.

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Part (b)

2 points

Calculate the mass of SO₂ released from the smokestack each year. Show your work.

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Part (c)

2 points

The plant could switch to coal that contains 0.8% sulfur, while still burning the same mass of coal and using the scrubber. Calculate the percent change in the plant's yearly SO₂ emissions. Show your work.

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Part (d)

1 point

Describe how SO₂ released from the plant leads to acid deposition.

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Part (e)

1 point

Explain one way acid deposition can harm forests.

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Part (f)

1 point

Besides the scrubber, the plant uses an electrostatic precipitator. Describe how an electrostatic precipitator reduces air pollution.

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Part (g)

1 point

On some winter mornings, a layer of warm air sits above cooler air near the ground in the valley where the plant is located. Explain how this condition affects air quality near the ground.

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