Question

Question: Explain why the numbers of molecules are not identical in the left- and right-hand bulbs shown in the centre illustration of Figure \({\rm{9}}{\rm{.27}}\).

Short answer

Since hydrogen gas gets effused faster than oxygen, there are different numbers of molecules of \({{\rm{H}}_{\rm{2}}}\) and \({{\rm{O}}_{\rm{2}}}\) gas in the left- and right-hand bulbs.

Step-by-step solution

Definition of molecule

A molecule is a group of two or more atoms bound together by chemical bonds.

Explaining difference in number of molecules

Before the stopcock is opened, the left bulb contains the lighter \({{\rm{H}}_{\rm{2}}}\) gas and the right bulb contains the heavier \({{\rm{O}}_{\rm{2}}}\) gas. When the stopcock is opened, the lighter \({{\rm{H}}_{\rm{2}}}\) gas moves through the opening faster than the heavier \({{\rm{O}}_{\rm{2}}}\) gas. The lighter \({{\rm{H}}_{\rm{2}}}\) gas effuses more rapidly than the heavier \({{\rm{O}}_{\rm{2}}}\) gas. So, a greater number of \({{\rm{H}}_{\rm{2}}}\) molecules moves from left to right than from right to left in a given time.

Therefore, the numbers of molecules are not identical in the left- and right-hand bulbs.