Which factor is most important to keep the same when comparing the hardness of solids? A. The temperature of the hot plate
B. The amount of each substance
C. The intensity of the light
D. The method of making a scratch on the material​

the formula would be mgso4

mgso[subscript]4

"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"

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements