Dalton's Law Formula

This is an empirical law that states that the total pressure exerted by a mixture of non-reacting gasses is equal to the sum of partial pressures of individual gasses.

Note: It is important to have non-reacting gasses as the pressure is dependent upon the number of moles of gas taken in the mixture. If the gasses react, the number of moles may change and the total pressure will not be equal to the sum of the partial pressure of gasses we took initially. 

Mathematically,

Ptotal = P1 + P2 + P3 + ….. + Pn

Where ‘Ptotal' is the total pressure of the mixture, and ‘P1, P2, P3 … Pn’ are the partial pressures exerted by individual gasses.

Example: A container contains three gasses, N2, O2 and Ar, with partial pressures of 23.3 kPa, 40.9 kPa and 13.7 kPa respectively. What is the total pressure inside the container?

Solution: 

PN2 = 23.3 kPa; PO2 = 40.9 kPa; PAr = 13.7 kPa

PT = ? 

PT = PN2 + PO2 + PAr 

PT = 23.3 kPa + 40.9 kPa + 13.7 kPa = 77.9 kPa

Question: In the chem lab, a student filled a balloon with 2 different gasses, CO2 and N2. The atmospheric pressure in the chem lab was 770.0 mmHg and the partial pressure of CO2 added to the balloon was 0.3255 atm. What was the partial pressure of N2 in the balloon?

Options:

(a) 522.6 mmHg

(b) 540.6 mmHg

(c) 640.6 mmHg

(d) 840.7 mmHg

Answer: (d)

Solution: 

PT = 770.0 mmHg; 

PCO2 = 0.3255 atm ( 760 mmHg /1 atm ) = 247.4 mmHg; 

PN2 =? 

PT = PCO2 + PN2 

PN2 = PT − PCO2 

PN2 = 770.0 mmHg - 274.4 mmHg = 522.6 mmHg

Learning the Dalton’s Law Formula - Dalton’s Law of Partial Pressure Formulas

Dalton’s Law Formula - Dalton’s Law of Partial Pressure Formulas is an important formula of mathematics that requires an ample amount of time and attention to understand. This formula allows you to determine the partial pressure of gasses inside a container.  You will have to practice different questions to become more proficient in using Dalton’s Law of Partial Pressure Formula. Here are some tips and tricks to understand this topic: 

• Before you move to Dalton’s Law Formula - Dalton’s Law of Partial Pressure Formulas, read the theoretical part of the concept thoroughly. It will give you a better understanding of Dalton’s law and make the formula easy to learn. 

• Read the textbook explanation of Dalton’s Law Formula - Dalton’s Law of Partial Pressure Formulas to get an idea of what the law states. 

• When you are studying Dalton’s Law Formula - Dalton’s Law of Partial Pressure Formulas, make notes of the most important points of the concept. Handwritten notes will make the learning process a lot easier during exam preparations. 

• Once you have learned Dalton’s Law Formula - Dalton’s Law of Partial Pressure Formulas, go through the solved example provided in your textbooks and reference books to understand how to apply the formula in different types of questions.

• Try out unsolved exercises, based on Dalton’s law formula, given at the back of the chapter in your textbook to practice the applications of this formula. 

• Go through the sample papers and previous year's questions papers to get an idea of what type of questions related to Dalton’s Law Formula - Dalton’s Law of Partial Pressure Formulas can come in your final exams.