The Effect of Temperature on Solubility

PURPOSE:

To observe the effect of temperature on solubility for two different solutes, sodium chloride and potassium nitrate.

EQUIPMENT AND MATERIALS:

beakers (2) 400 – 600 mL

hot plate

solute 1: 10.0 g NaCl

solute 2: 10.0 g KNO3

glass stirring rod

solvent: distilled water (20 mL total)

goggles

tap water

test tube rack

tongs

test tubes (2) 18 mm x 150 mm

10mL graduated cylinder

PROCEDURES:

  1. Set up equipment as shown below: FILL beakers with about 400 mL tap water
  1. Put one beaker of tap water on the hot plate to start heating up for the HOT WATER BATH (get this started because it takes a while to heat up the water)
  2. Measure out 10.0 g of NaCl using a weigh boat and balance (put NaCl in a test tube)
  3. Use a 10 mL graduated cylinder to measure out 10.0 mL of distilled water.
  4. Add the 10 mL of distilled water to the small test tube containing NaCl.
  5. Stir the solution with the glass stirring rod for several minutes until it is saturated.
  6. Record your observations for “INITIAL NaCl” (make a DRAWING and write observations)
  7. Put the test tube of NaCl into the HOT WATER BATH.
  8. Heat the sodium chloride solution until the water is near boiling and stir the solution
  9. While the NaCl is heating up in the hot water bath, measure out the 10.0 g of KNO3. Put this into a new test tube. Add 10 mL of distilled water. Stir the solution for several minutes until it is saturated.
  10. Record your observations for “INITIAL KNO3”
  11. Record your observations for NaCl in the hot water as “HEATING NaCl”. Take the NaCl out of the hot water bath using TONGS. Put the NaCl test tube in the beaker of cold tap water.
  12. Cool the NaCl test tube in a beaker of cold tap water for 5 to 10 minutes.
  13. Record your observations as “COOLING NaCl”
  1. Record your observations for KNO3 in the hot water as “HEATING KNO3”. Take the KNO3 out of the hot water bath using TONGS. Put the KNO3 test tube in the beaker of cold tap water.
  2. Cool the KNO3 test tube in a beaker of cold tap water for 5 to 10 minutes.
  3. Record your observations as “COOLING KNO3”

OBSERVATION: DRAW PICTURES of what you see and WRITE OBSERVATIONS

Solute: /

Observations: Initial

/

Observations: Heating

/ Observations: cooling
NaCl
KNO3

Questions & Conclusions:

  1. Use the graph on the right to estimate the amount of NaCl that dissolved in 10 g of water at room temperature. (~22ºC)

LOOK AT THE Y-axis UNITS (HINT, HINT)

  1. How much of the KNO3 dissolved at room temperature? (See #1 for HINT and room temp. info)
  1. How much of the NaCl dissolved after heating to 100ºC?
  1. How much NaClprecipitated out of solution when you cooled the solution from 100ºC to ~22ºC?