1) A student failed to clean their test tube and had an impurity that is insolub

Question

1) A student failed to clean their test tube and had an impurity that is insoluble in water. What effect would this have on the molar mass determination ( too high, too low or no change) ? Explain your answer.

2) A spike in temperature is often seen when a solid is first dissolved into water water. Provide an explanation for this initial increase.

3) Compare the molar mass you calculated for the unknown in part B to the possible compounds used in Table 2. Which compound do you think your unknown was? Determine the percent error of your calculation. Percent error = Actual - Experimental/Actual x 100.

4 ) List 2 sources of error that you could have had in part B of this experiment. For each indicate whether the error would cause the molar mass of the solute to be calculated as too high or too low.

( Please show all workings and solutions)

Explanation / Answer

1) if you fail to clean the test tube, you may have material inside the tube which will increase the mass of the content. If you have a greater mass, you will expect a different % mass fraction or mole ratios for your reactions. it will be higher since formula

MW = mass per mole

if you increase mass (mass of sample + dirt or odther material)

Therefore, expect a higher Molar mass

2)

The spike on temperature may be due to the heat of solution of the sample. When disolving material you may experience exothermic heat of solutions.

NOTE:

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