Pesticides are the chemicals that are used to kill or stop the growth of unwanted organisms. But these pesticides can affect the health of human beings. These are further classified as
a. Insecticides:
Insecticides like DDT ,BHC ,aldrin etc. can stay in soil for long period of time and are absorbed by soil . Th.y contaminate root crops like carrot, raddish, etc.
b. Fungicide :
Organo mercury compeunds are used as most common fungicide. They dissociate in soil to produce mercury which is highly toxic.
c. Herbicides :
Herbicides are the chemical compounds used to control unwanted plants. They are otherwise known as weed killers. Example sodium chlorate (NaClO₃) and sodium arsenite (Na₃ As O₃). Most of the herbicides are toxic to mammals.

CH₂ =CH₂ +HCI⟶CH₃ -CH₂CI
(A)                   (B)
Ethene   Chloroethane
CH₃CH₂CI+ NH₃⟶CH₃CH₂NH₂
(B)                        (C)
Chloroethane        Ethyl amine
A CH₂ =CH₂      Ethene
B CH₃CH₂CI     Chloroethane
C CH₃CH₂NH₂  Ethylamine

(a) mass of 1.5 moles of CoCl₂ = 1.5 x 129.9
= 194.85 g
194.85 g anhydrons cobalt chloride is dissolved in water and the solution is make up to one litre in a standard flask.
(b) \(6\%{V\over V}\)  aqeous solution contains 6g of methanol in 100 ml solution.
\(\therefore\) To prepare 500 ml of  \(6\%{V\over V}\) solution of methanol 30g methanol is taken in a 500 ml standard flask and required quantity of water is added to make up the solution to 500 ml.

Given data:
[NH₃] = 1.8 x 10^-2 M
[N₂] = 1.2 x 10^-2 M
[H₂] = 3 x 10^-2 M
K_c = ?
Solution:
N_2(g) + 3H_2(g) \(\rightleftharpoons \) 2NH_3(g)
\(K_c={[NH_3]^2\over[N_2][H_2]^3}={1.8\times 10^{-2}\times 1.8\times 10^{-2}\over 1.2\times 10^{-2}\times 3\times 10^{-2}\times 3\times 10^{-2}\times 3\times 10^{-2}}\)
= 1 x 10³l²mol^-2

Strong acids and strong bases exist in the fully ionised form in aqueous solutions as below:
H₃O⁺ + CI^- + Na⁺ + OH^- ⟶ Na⁺ + CI + 2H₂O
(or)
H₃O⁺_(aq)+OH^-_(aq)⟶2H₂O(1)⁰
ΔH^o =-57.32 KJ.
The H⁺ions produced in water by the acid molecules exist as H₃O⁺. Thus, enthalpy change of neutralisation is essentially due to enthalpy change per mole of water formed from H₃O⁺ and OH- ions. Therefore, irrespective of the chemical nature, the enthalpy of neutralisation of strong acid by strong base is a constant value which is equal to -57.32 KJ

The balanced equation for the combustion of ethane
C₂H₆ + \(\frac { 7 }{ 2 } \)O₂ \(\longrightarrow \) 2CO₂ +3H₂O
2C₂H₆ + 7O₂ \(\longrightarrow \) 4CO₂ + 6H₂O
To produce 4 moles of CO₂, 2 moles of ethane is required
To produce 1 moles (44 g) of CO₂ required
Number of moles of ethane
\(=\frac{2 \mathrm{~mol} \text { ethane }}{4 \not \mathrm{molCO}_{2}} \times 1 \not \mathrm{molCO}_{2}\)
= \(\frac { 1 }{ 2 } mole\quad of\quad ethane\)
= 0.5 mole of ethane

6Li + N₂ ⟶ 2Li₃ N

(i) 2KMnO₄ + 3H₂O₂ ➝ 2MnO₂ + 2KOH + 2H₂O + 3O₂ (Redox reaction)
(ii) CrCl₃ + 6H₂O ➝ [Cr Cl₂ (H₂O)CI. 2H₂O [Hydration reaction]
(iii) CaO + H₂O ➝ Ca(OH)₂ (Hydration reaction)

Gases which obey Boyle's Law and Charle's law or ideal gas equation PV = nRT are called ideal gases.
All gases whose behaviour is consistent with the assumption of kinetic theory of gases under all condition are called ideal gases.

	Ideal Gas	Real gas
(i)	Ideal gases obey all gas laws under all conditions of temperature and pressure	Real obey gas law only at low pressures and high temperature.
(ii)	The volume occupied by a gas molecule is negligible when compared to the total volume of the gas.	The volume occupied by a gas molecule is not negligible when compared to the total volume of the gas.
(iii)	The attractive forces between the molecules are negligible	The force of attraction are not negligible at all temperatures and pressures.
(iv)	They obey the ideal gas equation: PV = nRT	They obey the Vander waal's equation: \(\left(P+\frac{n^{2} a}{V^{2}}\right)(V-n b)=n R T\)
(v)	The collision between the molecules are elastic	The collision between the molecules are not elastic
(vi)	No energy is involved during, the collision of the molecules of ideal gas	Collision of molecules in real gas have attractive energy

(i) Electronic configuration is the arrangement of electrons in an atom. The outermost electron shell is often referred to as the "valence shell"determines the chemical properties.
(ii) Ionization energy and electron affinity is the amount of energy released or required in pulling out or adding an electron to a neutral atom. So both depend on electronic configuration of the element.