Structural isomers are chemical compounds that have
a)the same atoms that are arranged in different orders.
b)the same atoms that are arranged in the same order.
c) the same types of bonds that are bonding the same number of carbon atoms to different atoms.
d) different types of bonds that are bonding the same number of carbon atoms to different atoms.

A) the same atoms that are arranged in different orders.

Explanation: Structural isomers are those chemical compounds which have same molecular formula but different bonding patterns.  

These isomers are also called as constitutional isomers.

Eample: Butane and isobutane have same molecular formula i.e. but the arrangement of atoms differ as shown below.

the answer would be a

"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"