The gas produced when iron metal reacts with dilute hydrochloric acid is:

1. oxygen
2. hydrogen
3. chlorine
4. water vapour

When copper metal is added to a solution of silver nitrate, the colour of the solution changes to blue. This shows:

1. copper is less reactive than silver
2. copper is more reactive than silver
3. both are equally reactive
4. none of the above

Assertion (A): A chemical reaction is a process which involves the transformation of one or more substances into new substances with entirely different properties.

Reason (R): Breaking of chemical bonds between the atoms of reacting susbtances takes place to form new bonds between the atoms forming new substances called as products.

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 must be balanced in order to follow the law of conservation of mass.

Reason (R): A chemical equation called as skeletal equation may not have equal number of atom of each element present in the reactants and products.

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.