Recrystallization Experiment Chem 2013 by Catherine Pham [Student FVHS]

Pre Lab Disscusion

17phamcn289 — 2013-11-14 18:39:00 UTC

Recrystallization is one way of isolating an ionic compound from a solution. If several ionic compounds are present in an aqueous solution, then a precipitation reaction may be performed to remove the unwanted ions. In this experiment, a known amount of NaCl will be dissolved in some water, and then recrystallized by boiling off the water.

Purpose

17phamcn289 — 2013-11-14 18:44:36 UTC

To perform and master a recrystallization of an ionic compound.

To write a procedure for a simple experiment.

To calculate for percent error in an experiment.

To understand how results affect percent error.

To identify sources of error in experiments .

Materials

17phamcn289 — 2013-11-14 18:55:48 UTC

Graduated Cylinder

Materials

17phamcn289 — 2013-11-14 18:57:12 UTC

Flask

Materials

17phamcn289 — 2013-11-14 18:58:30 UTC

Rubber Tongs

Materials

17phamcn289 — 2013-11-14 18:59:17 UTC

Watch Glass

Materials

17phamcn289 — 2013-11-14 19:04:02 UTC

Heating Plate

Materials

17phamcn289 — 2013-11-14 19:06:12 UTC

Beaker

Procedure

17phamcn289 — 2013-11-18 19:04:48 UTC

1. Measure the beaker with and without the salt.

2. Pour 25mL water into the graduated cylinder.

3. Mix the 25mL of water and salt in the flask, to disslve the salt.

4. Pour the liquid from the flask back into the beaker.

5. Put the beaker on the heating plate.

6. Wait til 7-10 minutes until all the water evaporates out of the beaker.

7. Take the beaker off the heating plate with the rubber tongs and cool the beaker off for 5-10 minutes

until you are able to hold the beaker with your full hand.

8. Measure your final result.

Q2. If your percent error was positive, what logical sources of error might have been the cause? Explain. Answer this question regardless of what your results were.

17phamcn289 — 2013-11-19 03:49:43 UTC

A: If your percent error was postive some cause could've been that, maybe beforehand the flask had already contain little bits of salt because you didn't clean it before you use it for your experiment , another example could've been that someone before you had spilled salt on the scale which made your percent error greater.

Q3. If your percent error was negative, what logical sources of error might have been the cause? Explain. Answer this question regardless of what your results were.

17phamcn289 — 2013-11-19 03:52:24 UTC

If your percent error was negative then maybe one of the things that could've happen was that when you dumped the water and the salt into the beaker that some salt was still left inside the flask, another example is when all the water evaporated and the salt started crystalizing back it started popping and some of the salt got onto the watch plate.

Q4. Which ESLR or ESLR’s were addressed in the activity? State the ESLR and explain why in a short paragraph.

17phamcn289 — 2013-11-19 03:54:05 UTC

The ESLR's for us were communication and critical thinking, because you have to communicate in order to work together and get correct, precise , and accurate results. Critical thinking is common sense and you have to use critical thinking in this lab and it helps make things better.

Trial 1

2013-11-20 01:43:19 UTC

Trial 3

2013-11-20 01:46:22 UTC

Trial 2

2013-11-20 05:26:22 UTC