Many chemistry calculations are for materials that are in their standard state. One very useful rule for gases that does not necessarily require standard state conditions is the Ideal Gas Law eq 1.
Using the Ideal Gas Law, one can determine the value of any one of the four variables P, V, n, T if we know the value of the other three R is a constant. The Ideal Gas Law is a very handy equation for estimating gas properties at both standard and non-standard conditions.
Safety Emporium has all kinds of lab equipment such as stirring hot plates. The letters "STP" occur most commonly on a Safety Data Sheet after a physical property such as the density , flammable limit , or vapor pressure of the material. These properties are found in Section 9 physical and chemical properties of the SDS.
And the density of water is 0. Some textbooks define it differently than others, but the newest IUPAC standard temperature and pressure are:. This leads to a difference of about "0. Ever had your university lab notebook "torn apart" by a lab TA for "not enough information"? Yeah, it's primarily because science tends to rely on consistency and reproducibility to prove that something is credible.
If someone can't read your lab notebook and then reproduce your lab experiment without your input and correction, you haven't provided enough information to replicate that experiment precisely. IUPAC has defined such standards so that people have consistent atmospheric conditions to use for comparisons of data from different experimental trials for the same type of experiment.
That improves the accuracy to which an experiment can be reproduced. Chemistry Gases Gas Laws. Its behavior is described by the assumptions listed in the Kinetic-Molecular Theory of Gases. This definition of an ideal gas contrasts with the Non-Ideal Gas definition, because this equation represents how gas actually behaves in reality.
For now, let us focus on the Ideal Gas. We must emphasize that this gas law is ideal. As students, professors, and chemists, we sometimes need to understand the concepts before we can apply it, and assuming the gases are in an ideal state where it is unaffected by real world conditions will help us better understand the behavior the gases.
In order for a gas to be ideal , its behavior must follow the Kinetic-Molecular Theory whereas the Non-Ideal Gases will deviate from this theory due to real world conditions. Before we look at the Ideal Gas Equation , let us state the four gas variables and one constant for a better understanding. The four gas variables are: pressure P , volume V , number of mole of gas n , and temperature T.
Lastly, the constant in the equation shown below is R, known as the the gas constant , which will be discussed in depth further later:. Another way to describe an ideal gas is to describe it in mathematically. Consider the following equation:. An ideal gas will always equal 1 when plugged into this equation. The greater it deviates from the number 1, the more it will behave like a real gas rather than an ideal.
A few things should always be kept in mind when working with this equation, as you may find it extremely helpful when checking your answer after working out a gas problem. This law came from a manipulation of the Ideal Gas Law. This equation would be ideal when working with problem asking for the initial or final value of pressure or volume of a certain gas when one of the two factor is missing. Charles's Law describes the directly proportional relationship between the volume and temperature in Kelvin of a fixed amount of gas, when the pressure is held constant.
This equation can be used to solve for initial or final value of volume or temperature under the given condition that pressure and the number of mole of the gas stay the same. Volume of a gas is directly proportional to the amount of gas at a constant temperature and pressure.
Avogadro's Law can apply well to problems using Standard Temperature and Pressure see below , because of a set amount of pressure and temperature. Given a constant number of mole of a gas and an unchanged volume, pressure is directly proportional to temperature. Boyle's Law, Charles' Law, and Avogradro's Law and Amontons's Law are given under certain conditions so directly combining them will not work.
Through advanced mathematics provided in outside link if you are interested , the properties of the three simple gas laws will give you the Ideal Gas Equation. Here comes the tricky part when it comes to the gas constant , R.
Value of R WILL change when dealing with different unit of pressure and volume Temperature factor is overlooked because temperature will always be in Kelvin instead of Celsius when using the Ideal Gas equation. Only through appropriate value of R will you get the correct answer of the problem. It is simply a constant, and the different values of R correlates accordingly with the units given. When choosing a value of R, choose the one with the appropriate units of the given information sometimes given units must be converted accordingly.
Here are some commonly used values of R:. Because of the various value of R you can use to solve a problem. It is crucial to match your units of Pressure, Volume, number of mole, and Temperature with the units of R.
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