formula of sulphur trioxide

SO3

formula of phosphorus pentoxide

P2O5

formula of sugar

C12H22011

formula of methane

CH3

formula of ammonia

NH3

formula of ammonium

NH4

formula of hydroxide

OH-

formula of nitrite

NO2-

formula of nitrate

NO3-

formula of nitride

N3-

formula of bicarbonate

H2CO3-

formula of bisulphite

H2SO3-

formula of bisulphate

H2SO4-

formula of acetate

CH3COO-

formula of permangate

MnO4-

formula of sulphite

SO3 2-

formula of sulphate

SO4 2-

formula of carbonate

CO3 2-

formula of chromate

CrO4 2-

formula of dichromate

CrO7 2-

formula of manganate

MnO4 2-

formula of phosphate

PO4 3-

formula of phosphide

P 3-

why is the valency of inert gases zero

Because their valence shells are complete.

when do we put a polyatomic ion in brackets while represented as a formula

when the valency of the cation is more than 1.

which element is present in all acids

Hydrogen is omnipresent in acid

valency

it can be defined as the combining capacity of an atom of an element, or the number of electrons lost, gained, or shared [if valency is one].

metals with variable valency

copper [I & II] , iron [II & III], silver [I & II], lead [II & IV], mercury [I & II], tin [II & IV]

sulphur valencies

2, 4, 6

importance of molecular formulae

1. represents one molecule of an element/compound. 2. represents the elements in the compound 3. it enables us to calculate the molecular mass of the compound 4. represents the number of each kind of element and ion present in one molecule of a compound in a ratio.

amu of H

1

amu of He

4

amu of Li

7

amu of Be

9

amu of B

11

amu of C

12

amu of N

14

amu of O

16

amu of Fl

19

amu of Ne

20

amu of Na

23

amu of Mg

24

amu of Al

27

amu of Si

28

amu of P

31

amu of S

32

amu of Cl

35

amu of Ar

40

amu of K

39

amu of Ca

40

chemical equation

it is the symbolic representation of a chemical reaction using symbols and formulae.

reactants

the substances which are the starting material of the reaction and react with each other.

products

the substances which are created as a result of a chemical reaction.

aw of conservation of mass

Matter can neither be created nor destroyed; it can only transform from one form to another.

why do we have to balance chemical reactions

Because the number of reactants must be equal to no of products. A chemical reaction is simply a rearrangement of atoms; it breaks the law of conservation if not balanced.

limitations of a chemical equation

1. It does not mention the state of the reactants and products 2. It does not tell us the concentration of reactants and products 3. It does not tell us the time taken to complete the reaction 4. Does not tell us the rate at which the reaction proceeds 5. Does not say if heat is taken in or given out 6. Does not tell us the temperature, pressure, and catalyst required 7. Does not mention whether or not the reaction can be reversed

how can we improve chemical reactions

1. by using ⇌ for reversible reactions and → for irreversible reactions 2. adding the state of matter in brackets below the reactants and the products 3. adding (dil.) and (conc.) to show the concentration 4. adding (aq.) for aqueous state. 5. adding the temperature, pressure, and catalyst above the arrow 6. using arrow to indicate precipitate and evolved gas