The purpose of this lab was to identify an unknown solid by using a given solubility curve for three solids, NaCl, NaNO3, and KNO3. We were given a solid from which it could be NaCl, NaNO3, or KNO3. NaCl is sodium chloride, NaNO3 is sodium nitrate, and From the data given, we were supposed to create and execute a procedure which helped us find the identity of the unknown solid. Solubility curves are curves of different types of substances, which help us find the solubility in 100 grams of water at a given temperature. Solubility is a measure of the amount of solute that will dissolve in a given amount of solvent. A solute is the minor component in a solution. A solute is dissolved in the solvent. A solvent is the major component in a solution which dissolves another liquid, gas, or solid (solute). Together, a solvent and a solute form a solution.
Procedure
Materials
1. Big and small beaker
2. Pencil
3. Paper
4. Hot pan
5. Plastic tray
6. Thermometer
7. Test tubes
8. Erlenmeyer flasks
9. Stirring rods.
Procedure
1. Collect unknown solute
2. Fill the small water with 10 mL water. The water should be enough to submerge at least half of the small beaker in. We are using 10 mL of water because we were using a proportional amount of the solute and solvent in the solution.
3. Fill the big beaker with enough water so that half of the small beaker can get submerged into the water. This step is necessary so that the water from the small beaker does not evaporate when the temperature is being raised.
4. Measure the mass of a plastic tray. This has to be done first because the plastic tray's mass is not relevant in the lab. Hence, we will have to subtract the plastic tray's mass from the tray and solute mass to get the mass of the solute.
5. Put 4 grams of solute into the plastic tray.
6. Put the solute in the small beaker and stir for 1-2 minutes.
7. Heat the big beaker with the small beaker submerged halfway into the water in the big beaker until the temperature reaches 45 degrees Celsius.
8. After the small beaker reaches 45 degrees Celsius, stir for at least 1 minute. This is to dissolve as many particles as possible.
9. After stirring for 1-2 minutes, take the small beaker out and observe the mixture. If there is a solid, it must be NaCl. Since there is a solid, more solute must be added in the 10 mL.
10. Since the compound was NaCl, it should become saturated. Since our compound was NaCl, it did become saturated.
Data
Mass of solute- 4.00 grams
Volume of water- 10 mL
Temperature of heated water- 45 degrees Celsius
Temperature of room temperature water- 20 degrees Celsius
Mass of plastic tray- 2.04 g
Mass of plastic tray + solute= 6.04 g
Solute- NaCl
Conclusion
We identified the unknown solid as NaCl. One piece of evidence was how it became saturated when added to water at 45 degrees Celsius. This meant that our compound had a low solubility, which meant that it was NaCl as on the solubility curve, NaCl has the lowest solubility out of all of the compounds.When the temperature of the solute was 45 degrees Celsius and the mass was 4 grams, the solubility curve "told" us that our substance was NaCl. From the solubility curve, since the point of 45 degrees and 4 grams was near the graph for NaCl, this led to our prediction that our solute was NaCl. Also when the solute was not dissolved after step 7, the solute was saturated. Hence, the solute was NaCl. When the solubility increases the temperature also increases. Therefore, the relationship between solubility and temperature is a direct relationship.
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