Compounds can exist in all three states(solid, liquid, gas) provided that they can be heated/cooled enough(to their respective boiling/melting points). Thus water, ice, and steam all are compounds of hydrogen and oxygen.

Water is made of Hydrogen and Oxygen, which are gases at STP. 

Dissolved salts in potable water provide taste and are useful for living being like calcium and magnesium ions.

$22^{nd}$ of March every year is celebrated as the world water day.

Burning hydrogen with oxygen give rise to formation of water.

Henry Cavendish showed that water is made up of hydrogen and oxygen.

The number of molecules of water is 5. The formula is $CuSO _4. 5H _2O$.

The colour of hydrated copper sulphate is blue.

The colour of anhydrous copper sulphate is white.

The earth appears blue from outer space because 70% of the earth's surface contains water, i.e., water bodies like oceans, seas, rivers, lakes, etc.

The property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules is called surface tension. while washing clothes, detergents reduce the surface tension of the water molecule which causes the formation of foam and cleaning of clothes. 

Hard water contains chlorides, carbonates and bicarbonates of sodium and magnesium ions which combine with soap micelles and do not give lather with soap.

The number of molecules of water in $CoCl _2$ is 6. So the formula becomes $CoCl _2.6H _2O$.

Rain water and distilled water does not contain impurities.

The molecular weights of ammonia and water are 17 g/mole and 18 g/mole respectively.
4 moles of ammonia gives 6 moles of water.
$4 \times 17 = 68$ g of ammonia will give $6 \times 18 = 108$ g of water.
16.00 g of ammonia will give $16.00 \times \dfrac {108}{68} = 25.3$ g of water.

The molecular weights of ammonia, oxygen and water are 17 g/mole, 32 g/mole and 18 g/mole respectively.

66.00 g ammonia $= \dfrac {66.00}{17} = 3.88$ moles ammonia.
54.00 g oxygen $=\dfrac {54.00}{32.0}=1.6875$ moles oxygen.
4 moles ammonia reacts with 5 moles oxygen.
Hence, 3.88 moles ammonia will react with $3.88 \times \dfrac {5}{4} = 4.85$ moles oxygen but only 1.6875 moles oxygen are present. Hence oxygen is the limiting reagent.

5 moles of oxygen gives 6 moles of water.
1.728 moles of oxygen will give $1.6875 \times \dfrac {6}{5} = 2.025$ moles of water.
The mass of water obtained is $18 \times 2.025 = 36.51$ g of water.

Dissolved salts in water are important because
(A) They provide taste
(B) Growth of plants
(C) Minerals essential for body
Water contains dissolved salts which provide taste to water for drinking purposes. Also these salts are essential for growth and development of plants. These dissolved salts provide the essential minerals which are required for growth of body.

Dissolved gases can be removed from water by boiling.
Water contains certain gases in dissolved state. The higher the temperature of a solution becomes, the less a gas dissolves provided it doesn't react with the solvent. Consequently, heating/boiling a solution can expel the remaining gas.

Anhydrous $CoCl _2$ is blue in colour.

The gas-phase oxidation of hydrogen has been extensively studied over a wide range of temperatures and pressures.