What is true about a neutral atom? * a. The number of electrons and protons are always the same.
b. The number of neutrons is always the same as the number of electrons.
c. The number of protons may change.
d. The mass number can be found by knowing the number of electrons.
e. The mass number can be found by knowing the number of neutrons of the atom.

"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"

the awnser is group 12