chemistry for grade 7

1. First period - The first period has two elements - hydrogen and heliu..

The Seven Crystal System - Crystals along with suitable examples are listed in the table. System Axial distances Axial angles Examples Cubic a = b = c α = β = γ = 90° NaCl,KCl, Diamond, Cu, Ag Tetragonal a = b ≠ c α = β = γ = 90° White tin,SnO ..

Quantity Unit Symbol Length metre m mass kilogram kg Time second S Temperature kelvin K Amount of Substance mole mol Electric current ampere A Luminous intensity candela Cd ..

Calculate the vapor density and molecular weight of CO 2 gas occupying 200 mL and weighing 0.40 g at ST..

Catenation is the tendency of an atom to form bonds with identical atoms. In this group only sulphur has a strong tendency for catenation. Oxygen also shows this tendency to a limited extent. Thus the polyoxides and polysulphides of the following types are known: H 2 O 2 , H - O - O - H Polyoxides..

The molecular mass (or molar mass) is obtained either from the experimental data or from the vapor density of the compound by using the relationship, Molecular mass = 2 x Vapor dens..

A mixture of 97% oxygen and 3% carbon dioxide, called carbogen is used to revive persons affected by carbon monoxide poisoning, pneumonia, asphyxiation etc. b) Over production of hydrochloric acid in the gastric juice causes acidity. Health salts mostly contain sodium hydrogen carbonate, which rea..

An example of sharing of three pairs of electrons (Triple bond) Two atoms of nitrogen share three pairs of electrons to form one molecule of nitrogen (Fig. 3.6). Note : ..

Similarly, when hydrogen gas and iodine vapours are heated in a closed vessel at a constant temperature, 717K, the two react to form hydrogen iodide. In the beginning, the colour of the reaction mixture is deep violet due to the presence of iodine. But as the reaction proceeds, the intensity of th..