 ## GOB Chemistry

Learn the toughest concepts covered in your GOB - General, Organic, and Biological Chemistry class with step-by-step video tutorials and practice problems.

Gases, Liquids and Solids

# Dalton's Law: Partial Pressure (Simplified)

Partial Pressure (PGas) is the pressure exerted by an individual gas within a container.

Partial Pressure of Gases
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concept

## Dalton's Law: Partial Pressure (Simplified) Concept 1 44s
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partial pressure is the pressure exerted by an individual gas within a mixture. So think of it as the gas is individual pressure, we're going to say in a container of un reacting, gas is total pressure of the container is the sum of partial pressures of each gas. Now this is known as the law of partial pressures. So basically the total pressure inside of a container comes from adding up all the pressures of each individual gas. So total pressure would equal the pressure of gas one plus gas two plus gas three and so on. If there are additional gas, is so just remember, the total pressure that container is experiencing is contributed by each of the individual gasses within it.

In a container of unreacting gases, total pressure of the container is the sum of the partial pressures of each gas. 2
example

## Dalton's Law: Partial Pressure (Simplified) Example 1 2m
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here we're told that a sample of neon gas exerts a pressure of 1. atmospheres inside a cylinder. Some nitrogen gas is also present at a pressure of 500 tour. What is the total pressure inside the cylinder? So remember, we just learned about the law off partial pressures, which tells us that the total pressure felt inside of a container, or in this case, a cylinder comes from adding up the partial pressures of each gas present. So in the container, we have neon gas, and we also have nitrogen gas. The total pressure is when you add their partial pressures together. Now the issue is we don't have the same units for these gasses. Neon is in atmospheres, but nitrogen is in tours. Since atmospheres is a standard unit we usually use for pressure. Let's convert the tour into atmospheres. So we're gonna have 500 tour and remember that for everyone atmosphere that's 760 tour. So when we do that, we're gonna get as our atmospheres 0.65789 atmospheres. Take that and plug it in. And when we do that, we're gonna get a total pressure of 2. atmospheres. Within our question, 1.85 has three SIG figs. 500 only has one sick fig here. If we went by 16 fig, this would round up to three, which is a pretty big round there in terms of our value. So it's just better to go. Let's go with the three Sig figs in this 1.85 Again, the question isn't asking for a number of sick fixing. Your final answer. We're doing this as continual, continuous practice in terms of determining Sig Figs again. Better to go with three sig figs. I know it's not the least number of Sig Figs, but going from 2.5 to 33 atmospheres. It's such a big increase better just to go with three sig figs. And then we have 2.51 atmospheres at the end. So now that we've seen this question, let's move on to the next video
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## Dalton's Law: Partial Pressure (Simplified) Concept 2 48s
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So we know at this point that the total pressure felt within a container is a result of adding up. All the partial pressures of the gas is present. Now, if we can focus on one of these gasses and we know it's moles, its temperature and its volume, we could also find its partial pressure. Now we're going to stay here. If you assume that the gasses behave ideally, then their partial pressures can be calculated from the ideal gas law. We're gonna say here that the pressure of that gas that I'm focusing on so let's call a gas one. We confined its partial pressure if we know it's moles. So moles one. Ours are gas, constant times the temperature of the container divided by the volume of the container. So here we're using the ideal gas law to just focus in on one gas and from it determine its partial pressure.
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example

## Dalton's Law: Partial Pressure (Simplified) Example 2 3m
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## Dalton's Law: Partial Pressure (Simplified) Concept 3 1m
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Now, when the percent composition of a gas is given, first determine its fractional composition. Now by fractional composition, we mean that it represents the percent composition of a gas divided by total percent. So here we have our fractional composition formula. So here we're going to say fractional composition, which we're gonna use em As a stand in Ford's variable equals the percentage of your particular gas. You're looking at divided by the total percent, which is 100%. Then we're going to say that we can calculate the partial pressure of the gas using its fractional composition and the total pressure. So that feeds into Dalton's Law. And Dalton's Law says that the partial pressure of a gas, let's say, call it gas A equals the fractional composition of gas a times the pressure total. Right? So, using fractional composition allows us to step into Dalton's Law to help us figure out the partial pressure of gases within any given container.
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example

## Dalton's Law: Partial Pressure (Simplified) Example 3 1m
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A cylinder of a gas mixture used for calibration of blood gas analyzers in medical laboratories contains 5% carbon dioxide, 12% oxygen and the remainder nitrogen at a total pressure of 146 atmospheres. What is the partial pressure of each component of this gas? All right. So We're going to say we have 5% co two We have 12% oxygen and if we did 100% minus the 5% and 12% That would give us the percentage of our nitrogen gas. So that will come out to 83% nitrogen gas. Now that we know each other percentages, we can figure out their fractional compositions and by extension or partial pressures. So for C. 02 so pressure of C. 02 equals its fractional composition, which is 5% divided by 100% Times the total pressure of 1 46 atmospheres. This tells me that the partial pressure of co two is about 7. atmospheres for that B 12%. So pressure of 02 equals 12% divided by 100% times the total pressure, So that will come out to 17.5 atmospheres. And then finally we have nitrogen gas. So that would be pressure of nitrogen gas equals 83%, divided by 100 Times 1 Atmospheres. So this comes out to approximately one 21.2 Atmospheres. So this will be the partial pressure of each gas component within the gas mixture of this cylinder.
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Problem

A gas mixture contains 72.8% chlorine and 27.2% neon by mass. What is the partial pressure of neon in the mixture if the total pressure is recorded as 809 mmHg?

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Problem

The partial pressure of N2 in the air is 593 mmHg at 1 atm. What is the partial pressure of N2 in a bubble of air a scuba diver breathes when he is 66 ft below the surface of the water where the pressure is 3.00 atm? 