'X' is CH₃-CH₂OH ethanol. It can be made unsaturated by heating it with cone. H₂SO₄ which is a dehydrating agent and removes water from it, thereby forming ethene.
CH₃-CH₂OH \(\xrightarrow[{}{H_2SO_4}]{Hot \ Conc.}\) H₂C = CH₂ + H₂O
                          Ethene

A is ethanol, C₂H₅OH
B is ethanoic acid, CH₃COOH
Equation: C₂H₅OH \(\overset {acidified \ K_2Cr_2O_7}{\longrightarrow}\) CH₃COOH

The reactions in which reactants combine to form products and then again decomposes to give initial reactants are called reversible reactions.
(i) N₂ + 3H₂ \(\longrightarrow\) 2NH₃    (ii) CaO + CO₂\(\longrightarrow\) CaCO₃
   NH₃\(\longrightarrow\)N₂ + 3H₂                CaCO₃ \(\longrightarrow\) CaO + CO₂

(a) because of anaerobic respiration; (fermentation)
(b) because of aerobic respiration
(c) because of anaerobic respiration in muscle cells.

In the formula \(m=\frac { { h }_{ 2 } }{ { h }_{ 1 } } =\frac { -v }{ u } \), the sign of m is determined by the signs of h₁ and h₂ . When m is positive, the image is virtual and erect. When m is negative, the image is real and inverted.

Monohybrid cross.

(a) Since the element A belongs to group II, it will have two valence electrons. On the other, the element B belongs to group 15 and so it will have 15 - 10 = 5 valence electrons.
(b) The electronic configuration of element A is 2 and so the valency is 2. On the other hand, the electronic configuration of the element B is 2, 8, 5 and so the valency is 3.

CH₃COOH

The above reaction is a decomposition reaction. The symbol \(\Delta\) represents the heat and the MnO₂ represents that it acts as a catalyst for the decomposition reaction to take place. Since the decomposition takes place in presence of heat, the reaction is thermal decomposition.

A substance 'A' which displaces 'B' from its solution in water must be higher in reactivity. Therefore, 'A' must be high reactivity metal, let us say zinc(Zn). The 'B' must be copper sulphate solution. This is because copper is least reactive than zinc.
CuSO₄+Zn\(\rightarrow\)ZnSO₄+Cu
In this reaction, zinc is oxidised to zinc sulphate and copper sulphate is reduced to copper metal. Thus this reaction is also called redox reaction.