Question

How do you find the pressure of a gas in an eudiometer tube?

Answer 1

Hint: The pressure is nothing but the force applied to the unit area of an object. If the force has unit Newton and the area is in meters then the unit of the pressure is Newton per meter. The pressure is also expressed in units of Pascal, torr, mmHg, etc.

The ideal gas equation relates pressure, volume, temperature, numbers of moles of gas, and the gas constant as follows:
${\text{PV = nRT}}$
A eudiometer tube is used to determine the pressure of the gas which is collected over the water. Here, Dalton's law of partial pressure is used to determine the pressure of the gas which is collected over the water.

Formula used: The Dalton's law of partial pressure is given as follows:
${\text{P = }}\sum\limits_{\text{i}} {{{\text{P}}_{\text{i}}}} {\text{ = }}{{\text{P}}_{\text{1}}}{\text{ + }}{{\text{P}}_{\text{2}}}{\text{ + }}{{\text{P}}_{\text{3}}}{\text{ + }}...$
Here, i represents the numbers of the gaseous components.

Complete step by step answer:
- In the eudiometer, tube gas is collected over the water. There are water vapors and hydrogen gas is present in the gaseous mixture.
- Here, the pressure of the water vapors is determined at a particular temperature at which the experiment is carried out.
- Here, Dalton’s law is used to determine the pressure of the gas.
${{\text{P}}_{{\text{total}}}}{\text{ = }}\,{{\text{P}}_{{\text{gas}}}}\,{\text{ + }}\,{{\text{P}}_{{\text{water}}}}$

To find out the pressure of the gas rearrange the equation as follows:
${{\text{P}}_{{\text{gas}}}}\,{\text{ = }}{{\text{P}}_{{\text{total}}}}\,{\text{ - }}\,{{\text{P}}_{{\text{water}}}}$
In this way, the pressure of the gas is determined using the eudiometer tube.

Note: The volume of gas produced in a chemical reaction is measured using the eudiometer tube. It is also used to determine the pressure of gas using the vapor pressure of the water. Here, Dalton's law of partial pressure is used. The law states that in the mixture of the non-reacting gases, the total pressure of the gaseous mixture is nothing but the sum of the partial pressure of all gases present in the mixture.