Some Basic Concepts of Chemistry

Some Basic Concepts of Chemistry

Chemistry is the study of atoms and molecules. To understand atoms and molecules, we’ve to dig deeper in Chemistry to understand its most fundamental laws and concepts.

Scientific Notation

It is a method to express vary large numbers in the form of N*10ⁿ where N is a number lying between 1.000 . . . . to  9.999 and n is an exponent which can’ve negative values also.

Dimensional Analysis

—> It’s a method for converting one measurement unit to another unit for easy calculation.

Important Laws

1. Laws of conservation of mass —>

It states that matter can neither be created nor destroyed during chemical reaction.

• Law of definite proportions/composition —>

It states that a compound always contains the exact same proportion of elements by weight.

• Law of multiple proportions —>

It states that if 2 elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in the ratio of whole numbers.

• Gay Lussac’s Law of gaseous volumes/ Law of definite proportions by volume —>

It states that when gases combine or are produced during a chemical reaction, they do it in a simple ratio by volume.

• Avogadro’s Law

It states that at the same temperature and pressure, volume of all gases contain equal number of molecules.

• Dalton’s Atomic Theory

It states that –

1. Matter comprises of indivisible atoms.
2. All atoms of a particular elements have a identical properties.
3. When atoms of different elements combine in a fix ratio, compounds are formed.
4. Chemical reactions just reorganises atoms.

Significant figures

They’re the numbers which help in accuracy and precision of a measurement such as: – in a number 223, three significant figures are present.

Mases

• Atomic mass –> It’s the number of nucleons in an atom.
• Atomic weight –> Average atomic mass is called atomic weight.

One atomic mass unit (AMU) = One-twelfth of the mass of one carbon-12 atom.

I-e 1 AMU = 1.66056*10^-24 g. but thesedays AMU is replaced by “U” which stands for unified mass.

• Molecular Mass –> It’s the sum of atomic masses of each element present in a molecule.
• Molar Mass —> Sum of atomic weight of elements of a compounds is called molar mass.

One mole = No of atoms in 12g of the ¹²C.

Unit of Molar mass is “U”.

Mass % of an element = Mass of that element in compound/Molar Mass of compound*100

Number of moles = Mass (given)/Molar Mass.

Amount of any substance can be expressed in any of the following ways: –

1. Mass % = Mass of solute/mass of solution*100
2. Mole Fraction –> It’s the ratio of number of moles of a particular element to the total number of moles of the solution.

If substance ‘A’ dissolves in substance ‘B’, then

Mole fraction of A = number of moles of A/number of moles of solution

• N_a/ N_a + N_b
• Mole fraction of B = N_b / N_a + N_b

• Molarity = It’s the concentration of a solution expressed as the number of moles of solute per litre of solution.

• Molality = It’s the number of moles of solute present in 1 kg of solvent.

                                  Molality (m) = number of moles of solute/ mass of solvent of kg.