23 because of 1
Piece of bread
In my opinion I say 1 and 3 only or answer chose C
Answer: C. The sign of the enthalpy of the reaction reverses.
Explanation: Enthalpy of a reaction is the net heat absorbed or released during a chemical reaction.It is represented by 
. It is negative for exothermic reactions in which heat is released and is positive for endothermic reactions in which heat is absorbed.
When a chemical reaction is reversed the heat of the reaction changes its sign.
The decomposition of calcium carbonate is an endothermic reaction as heat is required to break the bonds and thus energy is absorbed.
When the reaction is reversed, the reaction becomes exothermic as now bonds are getting formed and energy is released.
Answer:
option C
Explanation:
Plants may serve as starting point when observing the carbon cycle. they undergo a process called photosynthesis that enables them to absorb and utilize carbon dioxide from the atmosphere and combine it with water. in the presence of the energy of the Sun absorbed by chlorophyll in plants, they are able to synthesize sugars and oxygen molecules. They play a huge in keeping the air clean with the carbon becoming a part of the plant. Plants and other organisms that die and become buried may be converted into fossil fuels made of carbon like coal and oil over millions of years. when these are then burnt by humans, most carbon then return to the atmosphere as carbondioxide.
