Predict the precipitate formed when sodium sulphate (${\mathrm{Na}}_2{\mathrm{SO}}_4$) reacts with barium chloride.

$\mathrm{Zn} + {\mathrm{CuSO}}_4\left(\mathrm{aq}\right) \to \mathrm{X} + \mathrm{Y}$

What is X and Y in the above reactions?

A, B and C are three elements which undergo chemical reaction according to the following equations.

${\mathrm{A}}_2{\mathrm{O}}_3 + 2\mathrm{B}\to {\mathrm{B}}_2{\mathrm{O}}_3 + 2\mathrm{A}$

$3{\mathrm{CSO}}_4 + 2\mathrm{B}\to {\mathrm{B}}_2({\mathrm{SO}}_4{)}_3+ 3\mathrm{C}$

$3\mathrm{CO} + 2\mathrm{A}\to {\mathrm{A}}_2{\mathrm{O}}_3+3\mathrm{C}$

Answer the following questions with reason.

(i) Which element is the most reactive?
(ii) Which element is the least reactive?
(iii) What is the type of reaction listed above?

Give an example of chemical changes in a reaction, where colour change is observed.

Give an example of chemical changes in a reaction involving

(i) formation of insoluble salt
(ii) formation of neutral products.

Give an example in chemical change of an exothermic and endothermic reaction involving carbon as one of the reactants.

What is meant by activity series of metals? Arrange the metals zinc, magnesium, aluminium, copper and iron in a decreasing order of reactivity?