Which reaction is endothermic?
2brcl mc019-1.jpg br2 + cl2 + 29.3 kj
2h2 + o2 mc019-2.jpg 2h2o + 572 kj
c + o2 mc019-3.jpg co2 + 394 kj
n2o4 + 59 kj mc019-4.jpg 2no2

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"

gold is my favorite solid.