Question

Read the descriptions below of two substances and an experiment on each. Decide whether the result of the experiment tells you the substance is a pure substance or a mixture, if you can .
Sample A is 100.mL of a clear liquid. The density of the liquid is measured, and turns out to be 0.77/gmL. The liquid is then heated in a flask until it boils. The vapor that rises off the boiling liquid is collected for 10 minutes and cooled until it condenses into a separate beaker. The density of the liquid that remains in the flask is then measured, and turns out to be 1.04/gmL.

Sample B is 100.g of a coarse grey powder with a faint unpleasant smell. 15.g of the powder are dissolved in ethanol. 0.5mg of the resulting black solution is carefully dropped onto a thick sheet of paper laid flat in a tray. After 30 minutes the initial round black stain has spread out and faded in color to a deep purple. Additionally, there is a dark green ring surrounding the inner stain.

a. Is sample A made from a pure substance or a mixture?
b. If the description of the substance and the outcome of the experiment isn't enough to decide, choose "can't decide.
c. Is sample B made from a pure substance or a mixture?
d. If the description Of the substance and the outcome of the experiment isn't enough to decide, Choose "can't decide.

Answer 1

Answer:

Samples A and B are mixtures

Explanation:

For sample A, we were told that the initial density of the solution is 0.77/gmL. After distillation, the liquid left has a density of 1.04/gmL. Apparently, A is a mixture of liquids.

As for sample B, the spread of the chromatogram resulting in different colours show that the sample B is not pure. It is a mixture of substances. A pure sample will yield only a single spot.