Chemistry Lab Question: Will Give Medal!

2. Why is it important to heat the baking dish or ramekin and cover in step #1?

3. Why is it necessary to achieve constant mass? How will you know when constant mass is achieved?

Question

Chemistry Lab Question: Will Give Medal!

2.	Why is it important to heat the baking dish or ramekin and cover in step #1?





3.	Why is it necessary to achieve constant mass? How will you know when constant mass is achieved?

anonymous · Answer

These are my directions: 
PROCEDURE

1.	Dry the ramekin or baking dish and cover in an oven overnight. Record the mass of the empty, dry dish and cover in Data Table entry #4.

OR

Place a clean, dry baking dish or ramekin with the cover ajar on the burner into the oven and heat to redness for 10 minutes at 160◦F. Discontinue heating and carefully use tongs hot pads to set the remove the dish and cover on a onto a cooling rack to cool. When cool enough to transport (about 5 minutes), measure the mass of the dish and cover. Record the mass of the empty, dry dish and cover in Data Table entry #2. Repeat the heating, cooling, and measuring procedure until the mass is constant. You have obtained a constant mass when two consecutive masses differ by no more than 0.01 g. Record the mass of the empty, dry dish and cover in Data Table entry #3 and #4.

2.	Half-fill the dish with about 3.0 g of Epsom salts (magnesium sulfate hydrate). Measure and record the exact mass in Data Table entry #1.

3.	Determine the mass of the hydrate by subtracting entry #4 from entry #1 in the Data Table. Record this result in Data Table entry #5.

4.	Gently heat (250∘F) the dish and contents with the cover ajar for two minutes. Gradually increase the temperature and heat strongly (about 400∘F) for 10 minutes. Cool, measure, and record the mass in Data Table entry #6.

5.	Repeat the strong heating with cover ajar for two minutes. Cool, measure the mass, and record reading in Data Table entry #7. If a third heating is necessary, heat the dish and its contents for one additional minute. Record the mass in the margin next to entry #7. Repeat the heating, cooling, and measuring process until two consecutive masses differ by no more than 0.01 g. Record the constant mass of the dish, cover, and anhydrous salt in Data Table entry #8.

6.	Determine the mass of the anhydrous salt by subtracting entry #4 from entry #8 in the Data Table and record in Data Table entry #9.

7.	Determine the mass of water lost by subtracting entry #9 from entry #5 in the Data Table and record in Data Table entry #10.