Safety Glasses Must Be Worn While Working in the Laboratory

EXPERIMENT VI

CHEMICAL FORMULA OF A HYDRATE

PROCEDURE

SAFETY GLASSES MUST BE WORN WHILE WORKING IN THE LABORATORY

1. Clean and dry a porcelain evaporating dish. Do not worry about stains. Set the evaporating dish on a clay triangle on a ring stand. Heat with a Tirrill burner, strongly for four to five minutes. Use the metal tongs to transfer the dish to the clay triangle. (While waiting for this dish to cool, you may clean and heat the second dish.) Test to see if the evaporating dish is cool without touching it. Bring the back of your hand near the evaporating dish and feel for any heat. If you feel heat, it is still hot! When cool enough to touch, go to step two. DO NOT ATTEMPT TO WEIGH A HOT EVAPORATING DISH.

2. Weigh the cool evaporating dish to the nearest 0.001 g. Record the mass on your data sheet.

3. Do not tare the balance. Add approximately, accurately 1.2 grams of hydrated magnesium sulfate to the clean evaporating dish. Weigh the evaporating dish plus contents accurately to within 0.001 g. Record the mass on your data sheet and describe the appearance of the sample.

4. (Set the second evaporating dish on the clay triangle to cool.) Put the evaporating dish on the ring stand. Heat slowly, or some of the sample will pop out of the dish. After a few minutes of gentle heating, heat vigorously for three minutes. Observe and record any changes in the appearance of your sample. Transfer the evaporating dish with sample to a triangle and allow the sample to cool. When cool enough to touch, weigh the evaporating dish containing the sample and record as the mass after the first heating.

5. Return the evaporating dish and sample to the ring stand and again heat for five minutes. Allow the sample to cool. Weigh the evaporating dish containing the sample and record as the mass after the second heating.

6. If almost all the water was removed during step four, the mass from step four and step five should agree to within 0.005 g. If so, record the mass from step five as the final mass of the evaporating dish and anhydrous salt. If not, put the evaporating dish on the ring stand and heat a third time for five minutes. Allow the sample to cool. Weigh the evaporating dish containing the sample and record as the final mass of the evaporating dish and anhydrous salt.

7. Repeat steps 2-6 with a fresh sample and a clean evaporating dish.

LABORATORY DATA SHEET

Appearance of the hydrated sample ______

Appearance of anhydrous sample ______

Trial / I / II
Mass of evaporating dish
Mass of evaporating dish
and hydrated salt
Mass of dish and sample after first heating
Mass of dish and sample after second heating
Final mass of evaporating dish
and anhydrous salt
Mass of hydrated salt
Mass of anhydrous salt (MgSO4)
Mass of water

Calculations:

LABORATORY DATA SHEET

Grams of H2O (previous page)
Grams of MgSO4 (previous page)
Molar mass of H2O
Molar mass of MgSO4
Moles of H2O
Moles of MgSO4
Moles of H2O / Moles of MgSO4 (value given to proper # of sig. figs.)
Moles of MgSO4 / Moles of MgSO4
Formula of hydrate
Name(s) of hydrate

Calculations:

LABORATORY REPORT SHEET

EXPERIMENT VI: CHEMICAL FORMULA OF A HYDRATE

Name ______Date ________

Partner ______Section ______

Appearance of the hydrated sample ______

Appearance of anhydrous sample ______

Trial / I / II
Mass of evaporating dish
Mass of evaporating dish and hydrated salt
Mass of dish and sample after first heating
Mass of dish and sample after second heating
Final mass of evaporating dish and anhydrous salt
Mass of hydrated salt
Mass of anhydrous salt (MgSO4)
Mass of water

Calculations:

LABORATORY REPORT SHEET

EXPERIMENT VI: CHEMICAL FORMULA OF A HYDRATE

Calculations: