Question

For all calculations, show all work and draw a box around the final answers. 1. Does the solubility of all solids in water increase with temperature? If not, list any exceptions shown in Figure 1 (do not include gases). 2. A 0.0500 M solution had an absorbance of 0.399. An unknown solution of the same solute in the same spectrometer had an absorbance of 0.231. Calculate the second solution's concentration, in molarity (Hint: recall that e and I are constant). 3. 10 drops of a 0.450 M NaCl solution was added to 5.0 mL of water. Assuming that the volume of each drop is 0.050 ml, find the molarity of the dilute solution. 4. In Part III, why is it not important to know the exact amount of water and CuSO4-5 H20(s) in Tube #1?

Answer 1

1) No, there are solids in which it is necessary to cool the solution so that its solubility increases. As for example: sodium hydroxide, ammonia, etc.

2) Absorptivity is calculated:

E = A / c * l = 0.399 / 0.05 * 1 = 7.98

The concentration of the second solution is calculated:

C = A / E * l = 0.231 / 7.98 * 1 = 0.03 M

3) The final concetracion is calculated:

C2 = 0.45 M * (10 * 0.05) mL / 5 + (10 * 0.05) = 0.041 M

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