Question

At the top of the Pikes peak, what is the boiling point of water?
A.It is ${{100}^{0}}C$
B. It is $>$ ${{100}^{0}}C$. since the pressure is less than at ground level
C. It is $<$ ${{100}^{0}}C$, since the pressure is less than at ground level
D. It is $>$ ${{100}^{0}}C$, since the pressure is greater than at ground level
E. It is ${{100}^{0}}C$ since the pressure is greater than at ground level

Answer 1

There is an equation that relates the pressure, volume and the temperature of gaseous substances. On reaching high altitudes, there is a change in atmospheric pressure and that results in a change of the boiling point.

Complete step by step answer:
In order to answer the question, we need to understand the role of pressure in maintaining the boiling point. Before that, let us get to know what boiling point is. Boiling point is the temperature of a liquid, which when is available, then transformation of the liquid takes place into a gas. However, it is influenced by pressure. Pressure is a downward force which prevents the molecules of liquid state to escape out the region. It is highly influenced by the ideal gas equation i.e $PV=nRT$. Suppose we open a cold drink bottle at sea level and on top of a mountain. In the sea level, pressure is high so there is high resistance. This prevents the cold drink from spilling very rapidly on opening. However, on top of a mountain, pressure is low. So, on opening, the volume expands rapidly according to the equation, and finally the cold drink spills out. As the resistance is less the substances will try to expand more and that is the reason for lowering of boiling point of liquids.
Now on coming to the question, Pikes peak has a high altitude, so the pressure will be less than ground level. As resistance is less, so the boiling point will be also less, i.e the tendency of becoming gaseous is more.

So, we obtain our correct answer as option C.

Note: It is to be noted that when we talk about the boiling point of a liquid, generally the boiling point is taken where the altitude is at mean sea level. At higher altitudes, the rate of evaporation of water is also more.