The law of combined gases concerns pressure, temperature and volume if everything else is kept constant (mainly molar gas, n). The most common form of the equation for the combined gas law is: The combined gas law defines the relationship between pressure, temperature and volume. It derives from three other gas laws, including Charles` law, Boyle`s law, and Gay-Lussac`s law. Below we explain the equation of the law, how it is derived and provide solutions to practice problems. The combined gas law is also often written as two different points in time. This means that if the combined gas law is extended and the moles of gas (n) are not kept constant, the ideal gas law is obtained. You can also go back from the ideal gas law to get the other gas laws by keeping different variables constant. In the case of the combined gases act, this would be done by keeping the moles of the gas or gases constant. If all these relations are combined in an equation, we obtain the combined gas law. The relation of the combined gas law works as long as the gases act as perfect gases.
In general, this is true when the temperature is high and the pressure is low. You can find out what makes a gas an ideal gas in the article “The Law of Ideal Gas”. The combined gas law is derived from the combination of Charles` law, Boyle`s law and Gay-Lussac`s law. Here we consider two different gas states, state 1 and state 2. Therefore, we will use the following form of the combined gas law. We know all variables except P2. We can also say that we look at a before and after state, so let`s use the following equation. Both k`s have the same value and can therefore be defined equally. This results in the following equation: Charlemagne`s law gives the relationship between volume and temperature. It is V/T = k. Boyle`s law tells us that P * V = k.
And finally, the Gay-Lussac law tells us that P * T = k. Suppose you have a sample of gas at 303K in a container with a volume of 2L and a pressure of 760mmHg. The sample is moved to a temperature of 340 K and the volume increases slightly to 2.1 l. What is the sample pressure now? Next, we rearrange the equation so that it solves for P2. First, multiply each side by T2. The new volume of gas is 1.6 l. As the temperature and pressure of the gas increased, so did the volume of the gas. The first step is to determine the variables we know.
Pressure, temperature and volume are specified for the original state 1. And pressure and temperature are given for state 2 because standard temperature and pressure are defined as 760 mmHg and 273K. The only variable we don`t know is volume 2 for which we need to solve. P is the pressure of the gas. T is the temperature of the gas. V is the volume of the gas. And k is a constant. The exact value of k depends on the moles of the gas. Here we look at two different states.
The original state with index 1 and the second state with index 2. First, note the variables we know: Our ultimate pressure is 812 mmHg. Also note that all units, except printing units, will be cancelled. To make calculations easier, let`s rearrange the equation to solve it for V2 before entering values. To do this, we multiply both sides by T2 and then divide by P2. They collect a gas at 620 mmHg and 177 K. At the time of collection, it occupies a volume of 1.3 L. What will be the volume of the gas as it moves to standard temperature and pressure? .
