Question

Two containers A and B are partly filled with water and closed. The volume of A is twice that of B and it contains half the amount of water in B. If both are at the same temperature, the water vapor in the containers will have pressure in the ratio of
A.$1:2$
B.$1:1$
C.$2:1$
D.$4:1$

Answer 1

The vapor pressure is described as the pressure applied by the vapors on top of the liquid surface. When the water is heated up to its boiling point, the molecules have sufficient energy to escape from the liquid. Therefore, we have to find the factors which depend on the vapor pressure to select the correct option.

Complete answer:
The vapor pressure is also called the equilibrium vapor pressure, which is described as the pressure applied by the vapor in equilibrium with its solid phase and liquid phase at a known temperature in a closed system. The equilibrium vapor pressure specifies the evaporation rate of liquid. The body which has a high vapor pressure at normal temperature is known as a volatile body. Vapor pressure is stated as the pressure applied by the vapors above the liquid surface and the pressure at which the water vapor is in thermodynamic equilibrium with its liquid state (or condensed state). The water will begin to condense at higher pressure.
The vapor pressure of water depends on the temperature. Because the temperature of water rises, the vapor pressure of water also rises and as the temperature reduces the vapor pressure of the water also drops. Therefore the vapor pressure of the water does not depend on the volume of the container and surface area of the container, because the liquid taken in both the containers is water then the ratio of their vapor pressure ${P_A}:{P_B}$ must be the same.

Therefore, the correct option is (B)- $1:1$ .

Note:
The kind of molecule existing in the liquid or solid also affects the vapor pressure. If the intermolecular forces existing between the molecules are powerful then the vapor pressure is low. If the forces between the molecules are comparatively less, then the vapor pressure is high.