The bar chart shows the approximate composition of clean, dry air by volume. Which gas is represented by the tallest bar, labelled P?
Question 1 Report
The bar chart shows the approximate composition of clean, dry air by volume. Which gas is represented by the tallest bar, labelled P?
Answer Details
Read the scale on the chart before comparing the bars. The vertical axis is percentage by volume, marked at 0, 40 and 80. Bar P rises almost to the 80 line, bar Q stands at roughly 20, and bar R is barely visible above the axis.
Those readings match the real composition of air: nitrogen about 78%, oxygen about 21%, and the remaining trace gases such as argon at about 0.9% and carbon dioxide at about 0.04%. So the tallest bar P is nitrogen. Choosing oxygen means confusing the tallest bar with bar Q beside it, and argon or carbon dioxide are far too small to reach anywhere near 78%. Always read values off the axis rather than judging heights by eye.
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