Partial pressure is a pressure exerted due to a single constituent of a gas present in the mixture of gases.
The combination of partial pressure by all the gases present in the system is the total pressure experience in the system due to gas. There are many examples in nature where you will come across partial pressure and this is applied in different aspects. Here is a list of partial pressure example:-
Opening Soda Bottle
Soda bottles are filled with carbon dioxide gas to preserve the soda in the container. When you open the soda bottle, this carbon dioxide gas is released into the atmosphere thus the effervescences are generated as a result of it.
Tomato from Refrigerator Dropped in Lukewarm Water
If you took out the tomato from the refrigerator and drop it in the water or if you drop the tomato in the warm water, you will notice small bubbles start gathering on the surface of the tomato.
This is because the heat energy comes in the equilibrium state, the excess heat is either taken out or absorbed. Due to this, the gas molecules are settled on the surface of the tomatoes because of surface tension.
Air Inside a Balloon
A balloon that is filled tightly with air may burst if the molecular force on the surface of the balloon increases.
The air molecules in the middle region of the balloon exert no force on the surfaces while the molecules present near the inner wall of the balloon exerts molecular force.
Cartesian Diver is a small toy diver you can easily design by tying a nut with thread underneath the driver model and putting it inside the bottle containing 3/4 volume of water.
The pressure due to water molecules is opposing the force exerted on the diver from the walls of the bottle. Also, the downward force is incident on the diver on putting the cap of the bottle. Hence, on applying additional force on the bottle in opposite directions, the molecular force on the surface of the wall from the sides cancels and the only force that sustains is the force from the cap therefore we can see that the diver dives into the water.
The blood circulating in the entire body parts of our body is also an example of partial pressure. The pressure exerted in the body due to the motion of the blood is between 90-120 mm of Hg
The manometer is a U-shaped device filled with either water, alcohol, or mercury and is used to measure the pressure in mm.
One end or both ends of the tube is opened. The pressure is felt on the fluid from one end of the tube and accordingly the level of the fluid decreases at this end and rises on the other end of the fluid.
Effervescences in Lime Soda
Use must have noticed on adding soda to the lime juice, the effervescence emerges out from the juice continuously for some time. This is because, lime juice is a citric acid and baking soda is nothing but sodium bicarbonate that reacts to produce salt, water, and carbon dioxide.
The effervescence is due to the carbon dioxide gas produced in the reaction. Hence, the pressure is due to the CO2 gas in the lime soda.
The moisture is created due to the partial pressure between the dry gas and the water vapor. The molecules of dry gas collide with the molecules of water vapor and form a moist.
The air in the atmosphere is a mixture of different gases like oxygen, nitrogen, carbon dioxide, etc. When we breathe in oxygen from the air, the pressure within the lung is only 116 torr while the pressure outside the lungs is actually 159 torr.
That means the pressure of oxygen gas is reduced when we inhale the oxygen. Implies that the pressure is felt in our lungs is a partial pressure due to a few gases and not the entire gases that are entering our body.
Air Pressure at Higher Altitude
As we go above the higher altitude, the atmospheric pressure is reduced. Since the pressure of the oxygen gas is also reduced, the pressure of the air entering our body will be still less and therefore we find it uncomfortable breathing.
Deep Sea Divers
Seawater is a mixture of different salts and minerals. Below the sea surface, the pressure increases thrice the atmospheric pressure.
Hence, it’s very difficult for a diver to breathe in at this pressure beneath the seawater level as the oxygen is mixed with an inert gas like He and therefore carries an oxygen cylinder along with him while diving.
The soap bubble is spherical in shape because of the surface tension and hence the pressure inside the bubble is P=4δ/r and is more than the atmospheric pressure 1atm. This pressure is due to the air molecules trapped inside the soap bubble. The pressure due to these molecules is exerted on the surface of the bubble.
Bubbles in Hot Water
As the heat energy is supplied to the volume of water, the bonds between the water molecules break, and the oxygen gas is released.
Thus we see that small tiny bubbles of oxygen are formed as the water starts acquiring the heat.
Air in the Atmosphere
The air is composed of different gases and a combination of all these gases gives the total atmospheric pressure of 1 atm. It is the addition of all the gases present in the air. The partial pressure due to nitrogen gas is 593 mm of Hg, oxygen exerts 159 mm of Hg, argon contributes 7.6 mm of Hg, and likewise, different gases will partially exert different values of pressure.
The oxygen is required to keep the flame burning while the carbon dioxide is utilized to turn off the blaze. The fire extinguishers are filled with carbon dioxide gas and hence are handy to extinguish the fire.
The carbon dioxide gas is stored in the pressurized cylinders maintaining the pressure at around 185 – 195 Pound force per square inch and thus becoming easy to release the gas on the target area.
Frequently Asked Questions
How is vapor pressure different from partial pressure?
The vapor pressure is formed due to boiling the liquids while the partial pressure is a term used for gases.
The vapor pressure is a pressure felt due to the number of vapors formed by the conversion of the liquid phase into gaseous, while the partial pressure is due to the force due to one constituent of a gas comprising the entire mixture.
What is Dalton’s Law of partial pressure?
If the pressure of the mixture of gas A and B is P then it is equal to the sum of partial pressure PA+PB.
Dalton’s Law states that the total pressure due to the mixture of the gases is the sum of the partial pressures felt due to the constituent of each gas present in that mixture.
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