2. Suppose the earth's atmosphere contained twice the number of molecules it does today. Would atmospheric pressure be greater than, equal to, or less than it is now?

Question

3. Two students make two different barometers. Although they are placed side by side so that they are both exposed to exactly the same atmospheric pressure, the column of liquid in the first student's barometer is significantly lower than the column of water in the second student barometer. Assuming both students made their barometers correctly, what explains the difference?
4. The average sea-level value for atmospheric pressure is 14,7 pounds per square inch, which same as 20.0 inches of mercury. If the atmospheric pressure is 0.85 atms, which of the follo values would correspond to atmospheric pressure as reported in a weather report?
31.1 inches of mercury, 29.9 inches of mercury, 25.4 inches of mercury

Answer 1

2. Atmospheric Pressure with Twice the Number of Molecules

If the Earth's atmosphere contained twice the number of molecules, the atmospheric pressure would be greater than it is now. Atmospheric pressure is directly proportional to the number of gas molecules present in a given volume, as described by the ideal gas law (PV = nRT). If the number of molecules (n) doubles while temperature (T) remains constant, then pressure (P) also doubles, leading to higher atmospheric pressure.

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3. Difference in Barometer Readings

If two barometers are placed side by side and exposed to the same atmospheric pressure, but one shows a significantly lower column of liquid (let's assume water) than the other, the likely explanation is the type of liquid used in each barometer.

Barometers typically use mercury or water. Mercury is much denser than water. A standard mercury barometer measures atmospheric pressure in inches of mercury, while a water barometer would need a much higher column to exert the same pressure because water's density is lower.

For example, standard atmospheric pressure of 14.7 psi corresponds to about 29.92 inches of mercury but would require a much taller column of water (approximately 34 feet). If the first student's barometer is using water and shows a much lower column, it could be due to using a much smaller diameter tube or it could be indicating a much lower height due to measurement error.

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4. Atmospheric Pressure in Inches of Mercury

If the atmospheric pressure is 0.85 atm, we can calculate the corresponding pressure in inches of mercury using the conversion factor that 1 atm = 29.92 inches of mercury.

To calculate:

\[ \text{Pressure in inches of mercury} = 0.85 , \text{atm} \times 29.92 , \text{inches of mercury/atm} \]

Calculating that gives:

\[ \text{Pressure in inches of mercury} ≈ 0.85 \times 29.92 ≈ 25.4 , \text{inches of mercury} \]

Thus, the atmospheric pressure of 0.85 atm corresponds to 25.4 inches of mercury, which is one of the options provided and falls in line with standard values.