Assertion (A): In the laboratory preparation of hydrogen, granulated zinc is reacted with dilute acid.

Reason (R): Granulated zinc contains copper as an impurity.

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): Pure hydrogen burns with a pop sound in air.

Reason (R): Hydrogen forms an explosive mixture with air.

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): Oxyhydrogen flame is used for cutting and welding metals.

Reason (R): For cutting and welding metals, a low temperature is required.

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.

Fill in the blanks:

(a) Hydrogen is …………… than air.

(b) Hydrogen is …………… soluble in water.

(c) Hydrogen burns with a …………… flame and …………… sound is heard.

(d) A metal …………… hydrogen in the reactivity series gives hydrogen with …………… .

(e) Hydrogen reacts with metal oxides to form …………… and …………… .

(f) Oxidation is the removal of …………… or addition of …………… .

(g) In redox reactions, oxidation and reduction occurs …………… .