Hydrogen

Q.

During photosynthesis, plants take in ___ gas and release ___ gas.

1. carbon dioxide, oxygen

2. oxygen, carbon dioxide

3. water vapour, methane

4. oxygen, methane

Q. The most abundant element present in the universe is.

Q. When metal X reacts with dilute $\text{HCl}$, bubbles of gas Y are formed. Moreover, when this metal X reacts with cold water, it will again produce gas Y. Identify X and Y.

1. X:- Copper, Y:- Hydrogen
2. X:- Potassium, Y:- Oxygen
3. X:- Calcium, Y:- Oxygen
4. X:- Sodium, Y:- Hydrogen