Magnesium chloride is an important coagulant used in the preparation of tofu from soy milk. its solubility in water at 200c is 54.6 g/100 g. at 800c, its solubility is 66.1 g/100 g. a mixture is made up of 16.2 g of magnesium chloride and 38.2 g of water at 200c.
(a) is the mixture homogeneous? if it is, how many more grams of magnesium chloride are required to make a saturated solution? if the mixture is not homogeneous, how many grams of magnesium chloride are undissolved?
(b) how many more grams of magnesium chloride are needed to make a saturated solution at 800c?

(a) Homogeneous. 4.7 g of MgCl₂.

(b) 9.1 g

Explanation:

(a)

At 200°C, we can dissolve 54.6g of MgCl₂ in 100 g of water. The mass that we could dissolve in 38.2 g of water is:

Since we can dissolve up to 20.9 g of MgCl₂ and we added only 16.2 g, the mixture is homogeneous and we could add 20.9 g -16.2 g = 4.7 g of solute to make it saturated.

(b)

At 800°C, we can dissolve 66.1 g of MgCl₂ in 100 g of water. The mass that we could dissolve in 38.2 g of water is:

Since we can dissolve up to 25.3 g of MgCl₂ and we added only 16.2 g, we could add 25.3 g - 16.2 g = 9.1 g of solute to make it saturated.

thats how its supposed to be

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.