If 8.00 kJ of heat are added to 200. g of water

Question

at 20.0 ◦C, what is the final temperature of
the water

Answer 1

Hydrogen peroxide decomposes into water
and oxygen when exposed to heat or light.
A tightly capped bottle of hydrogen peroxide
is placed on a balance and exposed to light for
three weeks. The mass reading on the balance
does not change. This is an example of

Answer 2

You should make your posts separate. They have a better chance of being answered that way.
#1,
q = mass x specific heat x (Tfinal-Tinitial)

#2.
Conservation of mass.