Explanation:
(a) It is known that relation between energy and mass is as follows.

where, E = energy
m = mass
c = speed of light =
m/s
As it is given that mass is
kg. So, putting the given values into the above formula as follows.

=
= 
Therefore, we can conclude that the energy produced by the reaction between one electron and one positron is
.
(b) When gamma ray photons are produced then they will have the same frequency. Relation between energy and frequency is as follows.
E =
..... (1)
where, h = plank's constant = 
= frequency
Also,
........ (2)
Hence, equating equations (1) and (2) as follows.
=
So,
= 
= 
Thus, we can conclude that the frequency is
.
The concentration of a and b will decrease while c will increase provided all other physical quantities are kept constant in the reaction
3. Silicon Dioxide
4. Phosphorus Tetrabromide
5. Iron(II) sulfate
6. Sulfur hexafluoride
7. Nitric acid
8. Lithium sulfide
9. Hydrogen chloride
10. Magnesium bromide
I think that’s what it is,sorry if I’m wrong.