Separation of a MixtureSeparation of a Mixture / Lab /

Background:

It is often necessary to separate mixtures of two or more substances. There are different ways of accomplishing this process. It might be a purely physical procedure such asdistillation in which substances of different boiling points are involved. Another way to physically separate a mixture is by the differences in the solubilities of the components of the mixture. In this experiment a mixture of sand and salt will be separated based on differences in solubility first and then by distillation. Once the separation is complete, it is possible to determine what percentage of the original mixture consisted of salt.

Purpose:

To separate the components of a mixture based upon physical characteristics of each component within the mixture and then to determine how well the procedure was carried out by calculating percent yield.

Materials:

Small beaker / Wash bottle / Hot plate
Balance / Water / Rubber mitt
Test tube with mixture / Florence flask / Wire gauze
Filter paper / Ring stand / Paper
Pencil / Ring
Funnel / Drying oven

Procedure (DAY 1):

  1. Record the mass of your emptybeaker
  2. Pour the contents of the test tube containing the salt/sand mixture into your beaker. Record the mass of the beaker and the mixture together.
  3. On a piece of filter paper and write your name around the edge in pencil.
  1. Fold the filter paper as shown in the diagram below (be sure your name is visible), and record the mass of the empty filter paper. Place the filter paper in the funnel.
  1. Using a wash bottle, add approximately 20.0 mL of water to the sand/salt mixture and stir until all of the salt has dissolved.
  2. Obtain and record the mass of a clean, dry Florence flask. Place the Florence flask under the funnel as demonstrated with the ring stand.
  3. Filter the salt solution through the funnel containing the filter paper into the Florence flask. Note: Most of the sand should remain in the beaker.
  4. Transfer the remaining sand by rinsing beaker with a small portion(approximately 2.00 mL) of water from the wash bottle. Pour the rinse water and sand through the filter paper. Repeat until all of the sand is emptied from the beaker. Note: Use as little water as possible to complete this step.
  5. When all of the mixture is out of your beaker, clean and dry it.
  6. When filtration is complete, carefully transfer the filter paper with the residue (sand) to the clean beaker and place beaker in drying oven.
  7. Meanwhile, place the Florence flask on a hot plate. When only white residue remains, use rubber mitt to take your Florence flask off of the hot plate. DO NOT PLACE FLASK DIRECTLY ON LAB BENCH. Put the flask on top of a wire gauze.
  8. When the Florence flask is cooled, place it on a piece of paper on which you have written your name. Leave the flask in the location determined by your teacher.

Procedure (DAY 2):

  1. When filter paper is completely dry, mass the beaker containing the filter paper and sand.
  2. Mass the cool Florence flask containing the salt.
  3. Complete all calculation, analysis & conclusion questions.

Data:

Mass of empty beaker (Day 1):______grams

Mass of beaker and mixture (Day 1):______grams

Mass of filter paper (Day 1):______grams

Mass of empty Florence flask(Day 1):______grams

Mass of beaker, filter paper & sand (Day 2):______grams

Mass of Florence flask and salt (Day 2):______grams

Observations: (Qualitative Data) Please use bullet format for your entries.

Calculations: Show all math for calculations and label answer with proper units.

Mass of original mixture:

Mass of sand recovered:

Mass of salt recovered:

Mass of total mixture recovered:

Analysis: Show all math for calculations and label answer with proper units.

Percentage of salt:

Percentage of sand:

Percent yield:

Conclusions:

  1. Define the following terms AND provide an example of each found in this experiment
  2. Heterogeneous mixture

Definition:

Example:

  1. Homogeneous mixture

Definition:

Example:

  1. Pure substance

Definition:

Example:

  1. Suppose a lab group reports a percent yield of 90%. What is a possible explanation for the “missing” product? Do not consider calculation mistakes, think about the procedure used.
  1. Suppose a lab group reports a percent yield of 105%.
  2. Is it really possible to collect more sand and salt than was originally present? Why or why not?
  1. What is a possible explanation for the “extra” product? Do not consider calculation mistakes, think about the procedure used.
  1. What if your mixture had contained small pieces of iron in addition to salt and sand, how could you modify the procedure used in lab in order to separate the mixture? (If you are not sure, look up some properties of iron that are different from sand and salt.)