We subtract the enthalpies of the reactants from that of the products:

Since this is < 0, this is an exothermic reaction.
Answer:The heat source for our planet is the sun. Energy from the sun is transferred through space and through the earth's atmosphere to the earth's surface.
Explanation:
Bro honestly I don’t understand either
The given above pretty much states already that with the presence of the calcium carbonate which acts as the buffer will allow the solution to withstand changes in acidity. The greater the amount, the higher chances that it will be able to withstand the said changes. Therefore, if Lake X had greater ppm of CaCO3 then, it will be able to withstand greater amount of acid rain.