Illustrated Guide to Home Chemistry Experiments

272 DIY Science: Illustrated Guide to Home Chemistry Experiments

CUTIOA nS

Ammonium nitrate is a strong oxidizer, and may detonate

if heated strongly. Sodium hydroxide is corrosive, reacts

strongly with aluminum (some commercial calorimeters

have aluminum bodies), and in high concentrations etches

or dissolves glass. Wear splash goggles, gloves, and

protective clothing at all times.

z

FIGURE 15-2:

Measuring the temperature of the contents of the calorimeter

POCEDURER
To achieve the highest accuracy, it’s best to have the solutes,
solvent (water), and calorimeter at room temperature. The
temperature of cold tap water is usually lower than room
temperature. If you have time to prepare beforehand, fill a two-
liter soft drink bottle or similar container with tap water and allow
it to sit for several hours to equilibrate to room temperature.

1. If you have not already done so, put on your splash
   goggles, gloves, and protective clothing.


2. Weigh 40.0 g of ammonium nitrate and record the
   mass in Table 15-1.


3. Use the graduated cylinder to measure 100.0 mL
   (100.0 g) of water.


4. Add the water to the calorimeter and replace the cover.


5. Measure the temperature of the water in the calorimeter
   as accurately as possible and record the temperature in
   Table 15-1. See Figure 15-2.


6. Add the ammonium nitrate to the calorimeter and replace
   the cover.


7. Stir the solution (or swirl the calorimeter) to dissolve the
   ammonium nitrate.


8. Watch the thermometer. When the temperature change
   reaches its maximum, record that temperature in Table
   15-1. Calculate the temperature difference and record it in
   Table 15-1.


9. Dispose of the spent solution and rinse out the
   calorimeter.
   Repeat steps 1 through 9, substituting 29.2 g of sodium
   chloride for the 40.0 g of ammonium nitrate.
   Repeat steps 1 through 9, substituting 20.0 g of sodium
   hydroxide for the 40.0 g of ammonium nitrate.

oALIpToN ACTIvITIES

If you have time and the required materials, consider

performing these optional activities:

• Repeat the experiment using 10.0 mL of concentrated
  (98%) sulfuric acid as the solute. (Caution:
  concentrated sulfuric acid is extremely corrosive.)
  Calculate the heat of solution for concentrated
  sulfuric acid.


• Repeat the experiment using 10.0 mL of 35% sulfuric
  acid (battery acid) as the solute. (Caution: 35%
  sulfuric acid is extremely corrosive.) Calculate the
  heat of solution for 35% sulfuric acid. Does this value
  differ from the value for concentrated sulfuric acid on
  a per mole basis? If so, propose an explanation.

dISoALp S : All of the solutions from this laboratory can

be flushed down the drain with plenty of water.

10.

11.