Assertion (A): PCl₃, is known as phosphorus trichloride while AlCl₃, is aluminium chloride and not aluminium trichloride.

Reason (R) : Phosphorus shows variable valency. Aluminium does not show variable valency

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Assertion (A): In a chemical reaction, the total mass of the products remains the same as that of the reactants.

Reason (R): A chemical reaction involves a simple exchange of partners and no new species are formed.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Assertion (A): A chemical equation is written to represent molecules.

Reason (R): This is necessary for the law of conservation of mass

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Assertion (A): Chemical combination always takes place between two elements.

Reason (R): A single substance is formed in a chemical combination.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.