Five students determined the solubility of KNO_3 in water at 30^degreeC. a. Can

Question

Five students determined the solubility of KNO_3 in water at 30^degreeC. a. Can the outlier be discarded from this data set b. Determine the mean, standard deviation, and confidence interval (at the level) of the data set. c. In preparation for a different solubility determination, a student measured the mass of an empty beaker (25.62 g) on a balance. Then, KNO_3 was added to the beaker and the mass recorded again as 35.18 g. Finally, water was added to the flask and the mass determined to be 50.03 g. The temperature of the mixture was increased until all of the solid had just dissolved. What was the solubility at this final temperature?

Explanation / Answer

For the given data values for KNO3 in water

a. No outliner value is valid in the given set of readings. They all fall withing the error values.

b. mean (X) = 45.7

standard deviation = sum(x-X)^2/5 = 0.64 + 0 + 0.16 + 0.01 + 0.09/5 = 0.18

                              = sq.rt.(0.18) = 0.424

confidence level at 90% level = 45.296 to 46.104

c. mass of KNO3 = 35.18 - 25.62 = 1.37 g

mass of water = 50.03 - 35.18 = 14.85 g

solubility = 1.37/14.85 = 0.092 g KNO3/water at this temperature.

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