Notes, abstracts, papers, exams and problems of Chemistry

Nucleus: The Center of an Atom

The nucleus is located at the center of an atom. It is very small and has a positive electrical charge due to the protons. The nucleus contains particles called protons and neutrons, which make up nearly all of the atom's mass.

Electron Cloud: The External Area of an Atom

The electron cloud surrounds the nucleus and is longer than the nucleus. It has an equal but negative electrical charge compared to the protons. The electron cloud contains particles called electrons, and their mass is negligible compared to the protons and neutrons.

Historical Development of Atomic Structure

In the 5th century, ancient Greeks proposed the concept of the atom. In 1808, Dalton discovered the existence of protons and electrons. In 1904,... Continue reading "Atomic Structure and Chemical Reactions: A Comprehensive Overview" »

ALKANES- Are a homologous series of similar hydrocarbons(compounds of carbon and hydrogen only) in which all the carbons are joined to each other with single covalent bonds.

Saturated Solution

Contains the maximum amount of solute for a given quantity of solvent at a constant temperature and pressure.

Solubility

Is the amount of solute that dissolves in a given quantity of a solvent at a specified temperature and pressure to produce a saturated solution.

Unsaturated Solution

A solution that contains less solute than a saturated solution at a given temperature and pressure.

Supersaturated Solution

Contains more solute than it can theoretically hold at a given temperature.

Miscible

Forming a homogeneous mixture when added together.

Immiscible

Liquids that are insoluble in one another.

Henry's Law

States that at a given temperature, the solubility of a gas in a liquid is directly proportional to the pressure of gas above the liquid.... Continue reading "Solutions and Solubility: Key Terms and Definitions" »

Experiment:Red Cabbage Indicator

Aim:To make our own indicator.

Background information:

• The Red Cabbage is red in acid solution

• Purple is a neutral solution

• Greenish-yellow is a base solution

• Red Cabbage contains a pigment molecule called FLAVIN(antocianina).

• The red cabbage juice will work over a wide pH range.To identified substances(acid or Bases)

Conclusion:The red Cabbage works as an indicator because we could identify the changes of each substance and classifies the bu colour of pH.For that we needed the ph scale.

Experiment :Acids and Bases

Aim:To find which substances are acid and bases by using different indicators

Materials:

1. Indicators(blue and red Litmus paper)

2. Samples

Procedure:Drop one drop of each substance on the indicators(the litmus

Electronegativity

Measure of the tendency of an atom to attract bonding pair of electrons.

Cation

Ion that has a positive charge.

Ionic Bond

Chemical bond formed between two ions with opposite charge.

Anion

Ion that has a negative charge.

Chemical Bond

Electrical attraction between nuclei and valence electrons that binds atoms together.

Covalent Bond

Bond formed when atoms share one or more pairs of electrons.

Non Polar Bond

Type of chemical bond where two atoms share a pair of electrons with each other.

Polar

Uneven distribution of charge.

Polar Bond

Type of chemical bond where a pair of electrons is unequally shared between two atoms.

Molecule

Neutral group of atoms that are held together by covalent bonds.

Molecular Compound

Chemical compound whose simplest... Continue reading "Chemical Bonding and Organic Chemistry" »

Properties of Metals:

Shiny, lustrous, can be polished, strong, and solid.

Nonmetals:

Dull, not lustrous, cannot be polished, weak, half are gases.

18 Families or Groups, 18 Periods:

Elements in the same group have common characteristics. Horizontal is period, vertical is family or group.

Periodic Law:

The PT is organized by atomic number Z. Elements with similar properties are in the same family.

Properties of Metalloids:

Have characteristics of metals and nonmetals. Located between metals and nonmetals.

Johann Dobereiner (1829):

Classified elements into groups of three, called triads.

John Newlands (1838-1898):

Law of Octaves (1863) suggested arranging elements in octaves.

Dmitri Mendeleev (1834-1907):

Published a table of elements organized by increasing... Continue reading "Evolution of the Periodic Table: From Triads to Actinides" »

Quartiles- divides the data set into four parts.

Q1= cuts data set so 25% of the data set falls below it and 75% of data falls above it.

Q2= cuts data set such that 50% of data falls below it and 50% of data falls above it.

Measure of Variability- A measure of variability is a value that describes the spread of a data set.

Measure of Relative Position- A value that indicates the position of a single value in relation to other values in a data set. 

Interquartile Range (IQR)- This value is the diffrence between the third and first quartile (Q3-Q1).

eliminates the bottom 25% and eliminates the top 25% where outliers would occur if present.

only considers middle 50% of data, leaving 50% of the data overlooked.

Combustion is a major source of air pollution emissions. The complete combustion of hydrocarbon fuel produces only CO₂ and H₂O as products, according to the following stoichiometry:

CH₄ + 2 O₂ CO₂ + 2 H₂O

a) Mass of air required for complete combustion of 500 kg of CH₄, assuming O₂ = 21% of air.

b) Mass of CO₂ produced from the above combustion

c) Calculate the mass of air required for combustion of 500 kg of benzene (C₆H₆).

a) Mass of O₂ required =

Mass of air required= 2000/0.23=8696  kg

b) Mass of CO₂ produced=

c)

Mass of oxygen required=

Mass of air required= 1538/0.23= 6686 kg

Mass of CO₂ produced = (6 x 44)/78 x 500 = 1692 kg

Fuel oil contains the following components (by weight); C- 88.3%, H- 9.5%, S- 1.6%, ash- 0.1%

1. Calculate the stoichiometric