134 DIY Science: Illustrated Guide to Home Chemistry Experiments
FIGURE 7-2:
Using a Beral pipette to bring the water mass up to 100.00 gPOCEDURER
dISoALp S : The weighing paper can be disposed of with
household waste.1.f you have not already done so, put on your splash I
goggles, gloves, and protective clothing.- Place a weighing paper or boat on the balance and tare
the balance to read 0.00 g. - Transfer potassium ferricyanide crystals to the weighing
paper until the balance reads as closely as possible to
16.63 g. Read the mass to 0.01 g and record it. (It’s
not important to have exactly 16.63 g of potassium
ferricyanide on the weighing paper, but it is important to
know the mass as exactly as possible.) - Transfer the potassium ferricyanide to the beaker, place
the beaker on the balance pan, and tare the balance to
read 0.00 g. - Use the wash bottle to transfer distilled water to the
beaker until the balance reads close to 100.00 g. Use
the dropper to add distilled water dropwise until the
balance reads as closely as possible to 100.00 g (Figure
7-2). Depending on the dropper, one drop of water may
weigh from about 0.05 g to about 0.02 g. When you have
100.00 g of water in the beaker, or as close to that as
you can get, read the mass to 0.01 g and record it. - Swirl the beaker gently until all of the potassium
ferricyanide has dissolved. - Place the funnel in the mouth of the labeled storage
bottle, and carefully pour the potassium ferricyanide
solution into the bottle. - Using the exact masses you recorded in steps 3 and
5, calculate the molality to the correct number of
significant figures and record that molality on the label.
Also record the date on the label. - Rinse the beaker, funnel, and volumetric flask and
stopper with tap water and then with distilled water, and
set them aside to dry.
CUTIOA nS
Potassium ferricyanide is irritating to skin and eyes.
Wear splash goggles and gloves.z