Answer:
Atmospheric pressure decreases as altitude increases. At the summit of a high mountain, the atmospheric pressure is 380 mmHg.
To calculate the partial pressure of oxygen at this altitude, we can use the following formula:
Partial pressure of oxygen = Total atmospheric pressure x Fraction of oxygen in air
Fraction of oxygen in air = 21% = 0.21 (given in the question)
Substituting the given values:
Partial pressure of oxygen = 380 mmHg x 0.21 = 79.8 mmHg
Therefore, the partial pressure of oxygen at the summit of a high mountain is about 79.8 mmHg.