What is common of volcanoes that have the most violent eruptions?

A. They feature magma with very high silica content.

B. They are shield volcanoes.

C. They feature magma with low viscosity.

D. They have no magma, but have much lava.

They feature magma with very high silica content.

Explanation:

A P E X

"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"