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D-6
REAGENTS AND EQUIPMENT
0.250 M NaNO2 (Sodium nitrite)
Tweezers
Squeeze bulb
0.082x M HSO3NH2 (Sulfamic acid)
Glass vial
50 mL buret
U-tube connected with clear tubing to a glass tube in a rubber stopper (special issue)
EXPERIMENTAL PROCEDURE
Safety glasses must be worn at all time in the laboratory.
Record all of your results on the Observations Sheet in ink.
Before assembling the apparatus, both the 250 mL Erlenmeyer flask and vial must be thoroughly cleaned.
Wash the flask and vial with a
mild soap solution. Rinse four times with tap water and then rinse twice
with deionized water.
Set up the apparatus as shown in Figure 1. Add approximately 350 mL of tap water at room temperature
(provided in a specially marked carboy) to the 400 mL beaker. Set up the buret so that the stopcock is at the
top and the open end of the buret is below the surface of the water in the beaker (See Figure 1).
A U-tube connected with clear tubing to a glass tube in a rubber stopper is provided for you to use. Insert
the U-tube into the mouth of the buret as shown in Figure 1, then lower the buret and U-tube to the bottom
of the beaker. Insert a rubber stopper into the mouth of the Erlenmeyer flask.
With the stopcock open, place a squeeze bulb (with the air expelled) over the tip of the buret and draw
water into the buret by slowly releasing the pressure on the bulb. Fill the buret so the water level is near the
48 mL mark. Close the stopcock if you need to remove the bulb to squeeze it again in order to draw more
water into the buret.
Run 1:
The sulfamic acid solution that you are to use has been prepared and is to be accuratedly dispensed from
burets that at set up in the laboratory for common use. For Run 1, accurately measure approximately 8.xx
mL of the sulfamic acid solution into the clean 250 mL Erlenmeyer flask. Record the initial and final buret
readings on your Observations Sheet. Measure the temperature of the sulfamic acid solution in the
Erlenmeyer flask with your thermometer to 0.1°C and record the temperature as t1 on your Observations
Sheet.
Note:
All buret readings must be recorded to 0.02 mL accuracy. A buret reading card must be used to
read burets accurately. For example, the initial reading might be 21.74
mL. (If most of your
readings end in 0 or 5, you probably are not making the readings correctly, and you will have
