Under certain conditions the solid and liquid states of water can exist in equilibrium how are these conditions indicated on the phase diagram for water

in the phase diagram the line between solid and liquid is where both phases available at the same time

The phase diagram of water has following features

a) Triple point : this is the point of intersection of three curves and is the point where all the three phases of water exist together

The triple point of water is 273.16K, and 4.58 mm Hg

b) Curves : these represents the presence of two phases together

the curve is shared by any two phases

i) melting curve : shared between liquid and solid phase of water

ii) vapour curve : shared between liquid and gas phase

iii) sublimation curve: shared between solid and gas phase of water

c) area : these are the portions of a phase diagram which represent single phase of water : solid, liquid or gas

Thus answer is :

Curves are used to indicate that the solid and liquid states of water can exist in equilibrium

"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"

20 drops hope this