Henry's Law Formulas and Examples
The law states that the solubility of an ideal gas in a liquid is directly proportional to the partial pressure of the gas over the liquid.
Mathematically,
P α x
P implies the partial pressure of the gas.
X implies the dissolved gas concentration.
The proportionality factor in the law is called Henry's law constant.
The units are correct. We rounded to one significant figure to match the number in the pressure. A 0.5 L bottle of cola has about 2 g (0.05 mol) of dissolved CO2.
Mathematically,
P α x
The units are correct. We rounded to one significant figure to match the number in the pressure. A 0.5 L bottle of cola has about 2 g (0.05 mol) of dissolved CO2.
Question: O2 is bubbled through water at 293 K. Assuming that O2 exerts a partial pressure of 0.98 bar. Calculate the solubility of O2 in gL-1. The value of Henry law constant (kH) for O2 is 34.84 k bar.
Options:
(a) 0.05 gL-1
(b) 0.08 gL-1
(c) 0.07 gL-1
(d) 0.01 gL-1
Answer: (a)
Solution: According to Henry’s law,
\[p_{o_2} = k_H \times x_{o_2} \text{ or } x_{o_2} = \frac{p_{o_2}}{k_H} \]
\[p_{o_2} = \frac{0.98 (bar)}{34.84 \times 10^3 (bar)} = 2.81 \times 10^{-5}\]
Mol of H2O in 1 L = 55.5
\[x_{o_2} = \frac{n_{o_2}}{n_{o_2} + 55.5} ( or) \frac{n_{o_2}}{55.5}\]
\[n_{o_2} = 2.81 \times 10^{-5} \times 55.5 = 1.56 \times 10^{-3} mol \]
Thus, solubility of \[O_2 = 1.56 \times 10^{-3} molL^{-1} \]
\[= 1.56 \times 10^{-3} \times 32gL^{-1} = 0.05 gL^{-1}\]
Applications of Henry's law
Henry's law is used in the production of carbonated beverages. The solubility of carbon dioxide increases under high pressure. But as the bottle of a beverage is opened under atmospheric pressure, the solubility decreases, as a result, the air bubbles are formed as soon as the bottle of a carbonated beverage is opened.
For those living in high altitudes, the concentration of oxygen in the bloodstream is low, as well as in the tissues. As a result, the person living the higher altitudes feels weak or is unable to think clearly. Such a condition is called hypoxia.
During underwater diving. Due to the hydrostatic pressure, there is an increase in the ambient pressure of the gas. According to Henry's law, the solubility of the games increases at the depth. The human tissues take upon more gas over time till its saturation. As the diver ascends, the decompression of tissues takes place and as a result, the solubility of the gases in the tissues also decreases. If the saturation is too high, there will be bubbles and they can cause blockages in the human capillaries.
There might also be distortion in the tissues and it is called decompression sickness. Hence, to prevent all the injuries, one must descend from the water as slowly as possible. This allows the excess gas to be carried to the lungs via the blood.
Simple Tips to memorise Henry's Law
Try Understanding the Derivation of the Formula
Learning the concept of the formula will help in becoming familiar and retaining the same for a long time. What one understands, one does not forget it easily. While deriving one formula, one comes across other formulas as well, which in turn aids better understanding.
Learn the Importance and Benefits of the Law in Real Life
While learning law or a formula, it is crucial to know the importance of it in day-to-day life. Knowing how much of an impact a law or a formula makes in our life makes it easy to remember the law itself. For example, one can remember Henry's law as the one that applies to carbonated drinks, this way it is easier to remind oneself of the law in exams.
Practice until Perfect
Try to solve the problems related to the law or using the formula. Try solving it with the help of a friend or a mentor. Doing this will help you know in which areas of the understanding you are facing the problems.
Create Flashcards for Easy Learning
After reading the law and the related concepts, write them again and again so it is retained in the memory. Make the flashcards so they can be easily re-read again and can be memorised in a short time before the exam. Making the separate flashcards for just the laws and formulas.
Draw Illustrations for Easy Learning
It is so helpful to look at a drawing and understand the concepts of the law or formula. Using graphics or even small drawings of the same can be beneficial to retain the law in the memory. Since our brain tends to retain a memory of the drawing more than the words themselves. When done in the exam, it may help in gaining some extra marks as well.
Ask for Help
Learn to ask and extend help as and when needed from tutors to friends. Learning is easy and fun when done with other peers. The concept is grasped in much less time since one can take less time to make it understand. Additionally, do not hesitate to ask for help from teachers and mentors, since they are there to help all the students learn better.
Keep making Notes and Refer to Vedantu
The library is a great learning resource and so is the Vedantu website. Visit the Vedantu site if and when needed to clear the doubts in minutes. There are ample resources to understand the concepts of physics better. Keep making notes to refer to them later. Revisioning whatever that is read before will help in retaining the memory.
