Question

Ringer's solution is used in physiology experiments. One liter of the solution contains 6 5g NaCl, 0.20g NaHCO_3, 0.10g CaCl_2 and 0.10g KCl. Assuming that one liter of water (with a density of 1.00g ml) is used to prepare the solution: a. Calculate the mass fraction and weight percent of NaHCO_3 in the solution. b. Calculate the mass fraction and weight percent of NaCl in the solution. c. Calculate the concentrations (in ppm) of K^+ ions and Ca^2+ ions in the solution.

Answer 1

a)

Mass fraction and weight percent of NaHCO3 in the solution.

We have 0.20g NaHCO3 in 1 L solution.

We will have to add mass of every component.

6.5g NaCl + 0.20g NaHCO3 + 0.10g CaCl2 + 0.10 g KCl + 1000 g water = 1006.9 g

Mass fraction = 0.20g/1006.9g = 0.00019

Weight percent = 0.20g/1006.9g * 100 = 0.019 %

b)

Mass fraction and weight percent of NaCl in the solution.

We have 6.5g NaCl in 1 L solution.

We will have to add mass of every component.

6.5g NaCl + 0.20g NaHCO3 + 0.10g CaCl2 + 0.10 g KCl + 1000 g water = 1006.9 g

Mass fraction = 6.5g/1006.9g = 0.00645

Weight percent = 6.5g/1006.9g * 100 = 0.645 %

c)

We have 0.10g KCl in our solution.

1) Convert to grams of KCl per L of solution.

KCl transferred is 0.10g and the solution's volume is 1 L (1000 mL), then

(0.10g)/(1 L) = 0.1g of KCl per L

2) Calculate the molarity of KCl solution.

Given MW 74.56 g/mol.

(0.1g KCl)*(1 mol KCl / 74.56 g/mol) = 0.0013 mol / L = 0.0013 M KCl solution

3) Find the concentration of solution in ppm of K.

Given KCl (aq) --> K+ (aq) + Cl- (aq)

Molarity calculated is 0.0013 mol/L for KCl.

0.0013 mol KCl * (1 mol K+ / 1 mol KCl) * (39.10 g K+ / 1 mol K+) = 0.0508 g K+ / L

In ppm 0.0508 g K+ * (1000 mg / 1 g) = 50.83 mg / L = 50.83 ppm