Major Laws of Chemistry

There are numerous laws of chemistry that form as the basis or the grounds of chemistry. These laws can be categorized and sub-categorized into many lists however, for the ease of the user we can define or categorize the laws of chemistry into major and minor laws. Here is look at some of the major laws of chemistry:

The law of conservation of mass: This is one of the most fundamental laws in all of chemistry. This law states that during a chemical reaction or a chemical change as well as a physical change, matter is neither made nor is it destroyed. With this said, we can also add by stating that during these changes, the mass of the final substance always stays the same whereas its properties change.

The law of definite proportions: No matter what source or sample of a compound we may use, it will always, according to the law of definite proportions have the same elements that will also be found in the same exact ratios of mass.

The law of multiple proportions: This is another major law of chemistry that aids in many chemical processes. This law states that if we have two entirely different compounds that are produced from two of the very same elements, then when we consider their mass in the form of ratios when the sample of these two compounds are combined, they will form a unique ratio that will always be equivalent to small whole numbers.

The law of conservation of energy: This is again a very important law of chemistry and is also similar to the conservation of mass. In this law, it is stated that the energy that is found in this entire universe is always and will always remain constant. It also goes on to say that energy, like mass can neither be destroyed nor can it be created.

Avogadro’s law: This law is a major gas law which states that two ideal gasses that contain the same volume at the same pressure and temperature will have the same number of molecules as well as atoms, ions, and electrons. The Avogadro’s law is also called the ideal gas law in which the pressure multiplied by the volume is equivalent to the multiplication of the number of molecules that are found in the gas with that of the temperature as well as the gas constant.

The concept that atoms play a fundamental role in chemistry is formalized by the modern atomic theory, first stated by John Dalton, an English scientist, in 1808. It consists of three parts:

· All matter is composed of atoms.

· Atoms of the same element are the same; atoms of different elements are different.

· Atoms combine in whole-number ratios to form compounds.

These concepts form the basis of chemistry.

Gas Laws

Gas has existed since the beginning of time; oftentimes, it was referred to as “air” or “oxygen;” however, in the late 18th century, “air” became known as gas, and people were able to distinguish between different types of gas. Towards the end of the 18th century, scientists started testing and developing laws that later became known as the “gas laws.” These laws describe properties of gases, and how they react in different situations. In order to understand the gas laws, we need to define a few terms:

Gas: a substance consisting of widely spread particles; it can expand indefinitely. This is also the third state of matter; it is not a solid or a liquid.

Pressure: the measure of force applied by another substance (such as a gas). It is commonly abbreviated as “P” (a capital letter P). Pressure can be measured in millimeters of Mercury (mmHg), torr, atmospheres (atm), Pascals (Pa), and kilopascals (kPa). All of the following measurements are the same, just different units, so you can use them to convert from one to the other. For the ideal gas law, the pressure will need to be in atmospheres. The conversions between these are as follows:

760 mmHg = 760 torr = 1.00 atm = 101,325 Pa = 101.325 kPa

If you need help setting up the conversions between pressure measurements, please refer back to the Mole section which also explains how to set up dimensional analysis.

Volume: the numerical amount of space occupied by a solid, liquid, or gas. It is commonly abbreviated as “V” (a capital letter V). Volume, in this situation, will be most often measured in liters, L.

Temperature: the measurement of the amount of energy seen in the motion of particles in a solid, liquid or gas. It can be measured on three scales: Fahrenheit, Celsius (sometimes referred to as Centigrade) and Kelvin. It is commonly abbreviated as “T” (a capital letter T). Temperature, in this situation, will most often be measured in Kelvin, K.

Amount of gas n: a lowercase “n” stands for the number of moles of a gas. This is a measurement in moles, so if you are given a mass in grams or kilograms, be sure to change it to moles first.

R (gas constant): when dealing with gas laws, R is a constant that means .0821 (L*atm)/(mol*K). The units are read as “liter-atmospheres per mole-Kelvin.” This label combines volume (measured in liters, L), pressure (measured in atmospheres, atm), mass (measured in moles, mol), and temperature (measured in Kelvins, K). In the Ideal Gas Law, the gas constant R = 8.3145 Joules · mol^-1 · K^-1 = 0.082057 L · atm·K^-1 · mol^-1

STP (Standard Conditions): STP stands for “standard temperature and pressure” and refers to conditions of 273 K (0 degrees C) and 1 atm. If in any of the laws, a variable is not give, assume that it is given. For constant temperature, pressure and amount:

1. Absolute Zero (Kelvin):0 K = -273.15^oC

T(K) = T(^oC) + 273.15 (unit of the temperature must be Kelvin)

2. Pressure: 1 Atmosphere (760 mmHg)

3. Amount: 1 mol = 22.4 Liter of gas

4. R = 8.3145 Joules · mol^-1 · K^-1 = 0.082057 L · atm·K^-1 · mol^-1