39. Magnesium chloride (MgCla) is a molecule held together by ionic bonds and co

Question

39. Magnesium chloride (MgCla) is a molecule held together by ionic bonds and completely dissociates in solution. If you are given a MgClz solution that has a concentration of 2.0 g/dL, what would be the molarity of that solution? Round your final answer to THREE decimal places. (7 points) 40. PART A) Calculate the osmolarity (in mOsM) of the MgCz solution you worked with in the previous question. Round your final answer to THREE decimal places. (5 points) PART B) If you added this solution to blood and then observed the erythrocytes with a microscope, DESCRIBE what you expect to see in terms of erythrocyte appearance and EXPLAIN HOW that change occurred by comparing this solution to the normal osmolarity of blood. USE TECHNICAL TERMINOLOGY! (5 points)

Explanation / Answer

39.
MgCl2 concentration = 2 g/dL = 2 g/100 mL = 20 g/L
MW of MgCl2 = 95.21 g/mol

M = (W/MW)(1000/V)
= (20/95.21)(1000/1000)
= 0.21 M

40.
MgCl2 -----> Mg+2 + 2Cl-
It can form three solutes.
So, osmolarity = 3 X molarity = 3 X 0.21 = 0.63 Osm/L

41.
Osmolarity of blood = 0.3 Osm/L
So, if we add 0.63 Osm/L MgCl2 solution to blood, it creates a hypertonic environment.
So, the water from RBC comes out by exosmosis and the cells will be plasmolyzed.

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