A synthesis or combination reaction is a reaction in which simple compounds combine to make a more complex one. The opposite of combination reaction is a decomposition reaction in which a single substance splits into two or more substances. We also have

single displacement reaction (in which a more reactive element displaces a less reactive element from its compound) and double displacement reaction (in which exchange of ions takes place between two compounds). Having a thorough understanding of the types of reactions will be useful for predicting the products of an unknown reaction.

(A) $\alpha$ Prashant performed several experiments and then noted down his observations in a tabular form as given:

S. No.	Observation	Conclusions Regarding types of Reactions Taking Place
(I)	When copper powder is heated in a china dish, the surface of copper powder turns black.	Combination reaction
(II)	Hydrogen gas is evolved when iron reacts with dil. HCl.	Decomposition reaction
(III)	A black precipitate is formed along with sulphuric acid solution when hydrogen sulphide gas is passed through copper sulphate solution.	Double displacement reaction
(IV)	When electricity is passed through molten aluminium chloride, aluminium metal is formed along with a gas.	Displacement reaction

Select the option that correctly describes the conclusions made by the student regarding type of reaction taking place:

(a) Both (I) and (II)
(b) Both (I) and (III)
(c) Both (II) and (III)
(d) (I), (III) and (IV)

(B) $\alpha$ When a metal X, which is used for coating iron articles, is added to a blue solution of a reddish brown metal Y, the colour of the solution gets discharged.

Select the option which correctly identifies the metals X and Y and the type of reaction taking place.

Option	Metal X	Metal Y	Type of Reaction
(a)	Zinc	Iron	Double displacement
(b)	Copper	Zinc	Double displacement
(c)	Copper	Zinc	Displacement
(d)	Zinc	Copper	Displacement

(C) Assertion (A): The reaction between copper oxide and hydrogen is an oxidation reduction reaction.

Reason (R): Copper oxide acts as an oxidising agent and hydrogen acts as a reducing agent.

(a) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true, and (R) is not the correct explanation of (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.

(D) Which of the following statement(s) are INCORRECT?

(I) The precipitation reactions produce insoluble salts.
(II) Displacement reactions are opposite of combination reactions.
(III) Decomposition reactions can be carried out only in presence of heat or light.

Options:

(a) Only (I)
(b) Only (III)
(c) Both (I) and (III)
(d) Both (II) and (III)

OR

(D) Ravi placed copper sulphate solution in an iron vessel and Mahima kept iron sulphate solution in a copper vessel for a few days. In which vessel the holes can be seen?

(a) Iron vessel
(b) Copper vessel
(c) Both (a) and (b)
(d) Holes will not appear in any vessel