Movement of electrons about a central nucleus is a concept by whom?

Bohr.

Explanation:

In 1913, N.Bohr proposed an atomic model for atom. He proposed that in an atom there is a central nucleus and electrons move around this center in a fixed path known as shell.

The shells or path have a fixed size and energy. The electrons do not lose energy during this movement.

There is possibility of energy change (emit or absorb) in an electron if they move from one shell to another.

"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 answer is true. hope it .