It is a sedentary rock. Limestone are usually affected by chemical weathering when rainwater (containing a weak carbonic acid) reacts with limestone. This causes the limestone to dissolve.
I've never done a reaction that involved just bond enthalpies before, so this is just a guess.
It's still products - reactants. The problem is the C=O bond. Do you count it once or twice? I'm going to choose once, but don't be surprised if it is incorrect.
Sum of the products - Sum of the reactants.
ΔH = 799 - 494
ΔH = 305
And that would be your answer to three places.
You spelled calendar incorrectly, the correct spelling is the one I previously wrote...Calendar
It is a principle that states that mass cannot be loss or gained in a chemical reaction.
