$A$ sample of $O_2$ gas is collected over water at $23\,^oC$ at a barometric pressure of $751\, mm\, Hg$ (vapour pressure of water at $23\,^oC$ is $21\, mm\, Hg$). The partial pressure of $O_2$ gas in the sample collected is

Write the important physical properties of liquids.

At higher altitudes,the boiling point of water lowers because:

Fill in the blanks:
$(1)$ The properties of gases were first measured by ......... .
$(2)$ The dipole-dipole interaction energy between stationary polar molecules is proportional to .......... .
$(3)$ The interaction energy between rotating polar molecules is proportional to .......... .
$(4)$ The bond energy of a hydrogen bond is about ......... $kJ \ mol^{-1}$.

What is the mathematical form of Dalton's Law of Partial Pressure?

The unit of pressure is equivalent to which of the following?