Question

Solubility of common salt in 100 ml water at 20°C is around 36 grams. Then why salt concentration in 1 litre sea water is only 35 grams where the temperature is about 30°C?

Answer 1

On average, seawater in the world's oceans has a salinity of approximately 3.5%, or 35 parts per thousand.

This means that for every 1 litre (1000 mL) of seawater there are 35 grams of salts (mostly, but not entirely, sodium chloride) dissolved in it.

Although a vast majority of seawater is found in oceans with salinity around 3.5%, seawater is not uniformly saline throughout the world.