Solubility: A Guided Inquiry Lab

Introduction

The purpose of the lab was for students to, using a given graph of solubility, decipher whether an unknown substance is NaCl, NaNO2, or KNO3. Students were not given a procedure, so they had to design their own. Materials included beakers, a hot plate, a balance, a thermometer, a graduated cylinder, and a stirring rod. 

Solubility- ability for a solute to dissolve in a solvent

Solubility Curve- a graph of the variation of changing temperature of the solubility of a given substance in a given solvent

Solute- smaller component of a solution that is dissolved into a solvent

Solvent- larger component of a solution that dissolves the solute

Solution- liquid mixture where the solute is evenly dispersed in the solvent

Saturated Solution- solution containing the maximum concentration of a solute dissolved in the solvent

Our Set-Up

Procedure

1) We first obtained materials: beakers, a hot plate, a balance, a thermometer, a graduated cylinder, and a stirring rod. We used the hot plate to control the temperature at 50℃, the balance to measure the mass of the substance to put into the water, the beakers to hold the substance and the water, the thermometer to measure the temperature of the water at 50℃, the graduated cylinder to measure the 10 mL of water to put into the beaker, and the stirring rod to stir the water and the substance. 

2) We filled the beaker with 10 mL of water. We did this because there wasn't enough of the mystery salt to completely saturate 100 mL solution. Then we placed the beaker onto the hotplate, where we then heat it up to 50℃.

3) We decided to first put 4.7 g of the mystery salt into the beaker because based off of the solubility chart, the saturation of the NaCl is 3.8 g at 50℃. We then stirred the mixture for a minute to make sure it was completely mixed. When the 4.7g of mystery salt formed precipitate when mixed with the water, then we knew it is NaCl. 

4) We heated up the water to 55℃ to double check that the salt was really NaCl, in case there were any experimental errors. There was still precipitate on the bottom, so we knew it was NaCl.

Data

The first trial, we had the temperature of the water at 50℃, and we had a total of 4.7g of the salt put into the water. We could see there was solid at the bottom. For the second trial, we had the temperature of the water at 55℃, and we had a total of 9.7g of salt put into the water. There was also solids at the bottom. 

Conclusion

My partner and I had substance C, and we identified it as NaCl. We know this because after mixing 4.7 g of the substance at 50℃ and stirring for a minute, there was still solid on the bottom of the beaker. To double check that the mystery substance really is NaCl, we raised the temperature to 55℃ and added in 5 more grams, and there was still solid at the bottom. This confirmed that the substance is NaCl. Under the circumstances that we had tested, NaNO3 and KNO3 would not have had solids remaining at the bottom. From this data, you can tell that as the temperature becomes higher, to solution becomes more soluble.