Which of the following are decomposition reactions?
A. 2LiOH (s) + CO² (g) --> Li²CO³ (s) + H²O (I)
B. K²CO³ (s) --> K²O (s) + CO² (g)
C. 2SO³ (g) --> 2SO² (g) + O² (g)
D. 2Na (s) + Cl² (g) --> 2NaCl (s)

The 2 decomposition reactions are:

B. (s) --> (s) + (g)

C. (g) --> (g) + (g)

Explanation:

Step 1:

A decomposition reaction is one in which a single compound breaks down into two or more products.

Step 2:

Let us examine each reaction if it satisfies the above rule.

A. 2 LiOH +   ---> +

In this reaction we have 2 reactants giving 2 products. Hence this is not a decomposition reaction.

B. ---> +

In this reaction a single reactant potassium carbonate gives rise to 2 products Potassium Oxide and carbon-di-oxide. Hence this is a decomposition reaction

C. ---> +

In this reaction a single reactant sulfur tri-oxide gives rise to 2 products sulfur di-oxide and oxygen. Hence this is a decomposition reaction.

D. + --->

In this reaction 2 reactants sodium and chlorine gives rise to a single product sodium chloride. Hence this is not a decomposition reaction.

Step 3:

The 2 decomposition reactions are:

B. (s) ---> (s) + (g)

C. ---> +

true tan speed = ang vel x radius

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.