Oxygen and sulphur at at the same group in the periodic table and they form bonding with hydrogen. h2o and h2s
but h2o is liquid and h2s is gas at room temperature why?

Below.

Explanation:

Because of the hydrogen bonding that occurs in water. Oxygen is more electronegative than sulphur and forms inter molecular bonding between the H+ and O- ions in  the water. This does not occur in H2S.

in chemistry, a solution’s concentration is how much of a dissolvable substance, known as a solute, is mixed with another substance, called the solvent. the standard formula is c = m/v, where c is the concentration, m is the mass of the solute dissolved, and v is the total volume