Which of the following statements about the reaction given below are correct?

MnO₂ + 4HCl ⟶ MnCl₂ + 2H₂O + Cl₂

(i) HCl is oxidized to Cl₂

(ii) MnO₂ is reduced to MnCl₂

(iii) MnCl₂ acts as an oxidizing agent

(iv) HCl acts as on oxidizing agent

1. (ii), (iii) and (iv)
2. (i), (ii) and (iii)
3. (i) and (ii) only
4. (iii) and (iv) only

Select from the following the statement which is true for bases.

1. Bases are bitter and turn blue litmus red.
2. Bases have a pH less than 7.
3. Bases are sour and change red litmus to blue.
4. Bases turn pink when a drop of phenolphthalein is added to them.

It is important to balance the chemical equations to satisfy the law of conservation of mass. Which of the following statements of the law is incorrect?

1. The total mass of the elements present in the reactants is equal to the total mass of the elements present in the products.
2. The number of atoms of each element remains the same, before and after a chemical reaction.
3. The chemical composition of the reactants is the same before and after the reaction.
4. Mass can neither be created nor can it be destroyed in a chemical reaction.

Consider the following statements in connection with the functions of the blood vessels marked A and B in the diagram of a human heart as shown.

(i) Blood vessel A — It carries carbon dioxide rich blood from the lungs.

(ii) Blood vessel B — It carries oxygen rich blood from the lungs.

(iii) Blood vessel B — Left atrium relaxes as it receives blood from this blood vessel.

(iv) Blood vessel A — Right atrium has thick muscular wall as it has to pump blood to this blood vessel.

The correct statements are

1. (i) and (ii) only
2. (ii) and (iii) only
3. (ii), (iii) and (iv)
4. (i), (ii) and (iii)