Difference between reaction enthalpy and heat absorbed by water

[Lori]

Homework Statement

Homework Equations

q = mCat

The Attempt at a Solution

I'm kinda confused the different between Hrxn and q? I know the reaction warms the water with q=mcat = 150*4.18*(59.5-20)=24766.5 J. This is the heat released from 1.25 grams of Ca which is 0.03 moles of Ca. But, the reaction equation only have calcium per 1 mole so i thought that i would divide q by 0.03 = 825550 J or 825KJ, but this is not an answer.

Can someone help me with these heat problems? Thanks

 

[Lori]

Nevermind everyone. It seems like i didn't enter enough decimals here. So, my answer is 794052

 

[Borek]

Exactly. Don't round down intermediate results during calculations (that is, report them rounded down, but calculate with a full accuracy, or at least several "guard digits").