Concentration?
Tuesday, February 23rd, 2010 at
8:12 AM
Each 200ml of an electrolyte solution designed for treating dehydration contains 0.47g of sodium chloride (NaCl), 0.30g of potassium chloride (KCl) and 3.56g of glucose (C6H12O6).
A)Calculate the concentration of potassium ions in the solution in mol L-1
B) Calculate the concentration of chloride ions in the solution in mol l-1
Filed under: Potassium and Being Sick
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As the questions ask for the concentration in mol/L, this signifies that Molarity has to be used. (Molarity = moles of solute / L of solution)
A.) To calculate the concentration of potassium ions (the solute), you must find the number of moles of the K+ ions. 0.30 g KCl x (1 mol KCl/74.6g KCl) x (1 mol K/1 mol KCl) <– to cancel out the units and get moles of K+ ion
= 0.0040 mol K+ ion
Since you have 200 mL of electrolyte solution, you have to convert it into liters to calculate molarity, so 200 mL / 1000 = 0.200 L.
Then Molarity = 0.0040 mol K+ion / 0.200 L solution = 0.020 M (the symbol for molarity)
B.) For this problem, you would do the same thing. To find number of mol Cl- ion, find # of mol of NaCl and convert to mol of Cl- ion:
0.47 g NaCl x (1 mol NaCl / 58.44 g NaCl) x (1 mol Cl- ion / 1 mol NaCl) = 0.0080 mol Cl- ion
Molarity = (0.0080 mol Cl- ion / 0.200 L solution) = 0.040 M