Which of the following reactions are exothermic?

 

$$\begin{gathered} 1) C + O2 → CO2 \\ 2) 2Mg + O2 → 2MgO \\ 3) CuSO4 + 5H2O → CuSO4.5H2O \\ 4) All the above \end{gathered}$$

Removing the contaminents if any in the water which causes harm to our health is involved in the purifying of water. 

This process involves chemicals. Chloramines, Hydrogen peroxide, Iodine are the chemicals which are used in purifying water.

An ionic bond is formed between two molecules when transfer of valency electrons take place between them. 

Colloids include gels, sols, and emulsions; the particles do not settle, and cannot be separated out by ordinary filtering or centrifuging like those in a suspension.

These Colloid substances consists of ultramicroscopic particles of one substance dispersed through another substance from which we cannot separate them.

Sugar water is not a colloid and it is a solution in which we can separate them.

ATP is a Adenosine Triphosphate.

ATP is 3 Phosphate groups attached to a Ribose attached to Adenine.

NH3, Ammonia is a neutral compound as the individual oxidation numbers elements that make up the compound NH3 are Nitrogen (N) and Hydrogen (H) sum to zero. 

We do not speak of the oxidation number of a molecule. We can speak of the oxidation numbers of the individual elements that make up the compound.

Here the oxidation number of Nirogen is -3 and that of Hydrogen is +1.

Now, NH3 = 1(-3) + 3(+1) = -3 + 3 = 0.

SO2 has a net dipole moment and has a bent shape in its structure as water molecule. Hence it is a polar molecule.