- Unknown Hydrate Number Mass Of Test Tube And Hydrate Grams Cusou X H2o 32 40 30 60 Mass Of Empty Test Tube Grams Mass 1 (70.2 KiB) Viewed 159 times
- Unknown Hydrate Number Mass Of Test Tube And Hydrate Grams Cusou X H2o 32 40 30 60 Mass Of Empty Test Tube Grams Mass 2 (56.23 KiB) Viewed 159 times
- Unknown Hydrate Number Mass Of Test Tube And Hydrate Grams Cusou X H2o 32 40 30 60 Mass Of Empty Test Tube Grams Mass 3 (31.98 KiB) Viewed 159 times
- Unknown Hydrate Number Mass Of Test Tube And Hydrate Grams Cusou X H2o 32 40 30 60 Mass Of Empty Test Tube Grams Mass 4 (30 KiB) Viewed 159 times
Hydrates are sold ionic compounds (salts) that contain water moleculos as part of their crystal structure. Ex: CuSO4-5 H2O(a) is a hydrate that contains one copper (lt) formula unit with 5 molecules of water attached. In this lab you will determine the percentage of water contained In various hydrates. When a hydrate contains water molecules it is said to be hydrated. When it has lost its water molecules, it is said to be anhydrous To find the percent water in a hydrate in which we know the formula, find the molecular mass of tho anhydrous salt and the mass of the water molecules. Add them together to get the mass of the hydrate. Put the molecular mass of all the water molecules and divide that by the total mass of the entire hydrate and multiply by 100. To name hydrates, just name the ionic compound and then use the same prefixes as used to name molecular/non-acids, to indicate the number of water molecules in the hydrate. The hydrate listed above is called copper (11) sulfato pentahydrato Purpose To find the percent of water in an unknown hydrate Safety Always practice safe laboratory procedures. Wear safety goggles. Wash your hands before toaving the lab. Dispose of sample in the correctly marked container. Be careful when handling hot glassware and equipment Procedure 1. Obtain an unknown sample of a hydrato. Record the number of that sample on your Data Table 2. Obtain a large Pyrex or Kimax test tube and weigh it to the correct number of significant digits on an analytical balance. Record this mass on Data Table. Note: Always use crucible tongs or a test tube holder when transporting a test tube. 3. Using a spatula, transfer approximatoly 2 grams of your unknown hydrate sample into the test tube. 4. Reweigh the test tube with the sample in it and record on Data Table 5. Subtract the two to determine the mass of your unknown. 6. Ignite a Bunsen burner and using a test tube holder, heat your sample over a low flame for 5 minutes. Then heat the test tube more strongly until no more droplets of water can be seen forming on the inside of the test tube. (About 10 minutes) 7. Remove the test tube from the flame and place on wire gauze to cool. 8. When no heat is felt when you hold your hand 1 to 2 cm from the test tubo, wait a few more minutes (The test tube needs to be at room temperature), and using your crucible tongs or test tube holder, reweigh the cooled test tube. Record this mass on your Data Table 9. To the cooled anhydrous hydrate, add about 5 mL d. water. Stir the mixture using a stirring rod. Careluny touch the outside of the test tube. Does it feel hot or cold? Record your observation on Data Table 10. Discard the solution in the appropriately marked container.
1. What is the name of the hydrato that you used in this experiment? 2. What is the formula of the hydrate that you used in this experiment? 3. From its formula, what is the percentage of water in your hydrate? This is your theoretical value. (Show work.) 4. From your experimental data, what is the percentage of water in your hydrate? This is your experimental value. (Show work.) 5. What is your percent error? x 100 Experimental value - theoretical value Theoretical value 6. Why is it important to hear the hydrate thoroughly? 7. Why must you use tongs or a holder to handle the test tube after heating? 8. What do the following symbols represent? a: (s) b. (a) 9. The mass of a test tube and hydrate was 35.2755 grams. The mass of the empty test tube was 23.7726 grams. The mass of the anhydrous salt and test tube was 31.0035 grams. a. Find the mass of the original hydrato. (Show work for credit.) b. Find the mass of the water lost after heating. (Show work for credit.)
c. What was the percent water in the hydrate? (Show work for crecht) 10. What is the percent water in calcium nitrate tetrahydrato? (Show work for credit.) 11. What is the percent water in lithium nitrato trihydrato? (Show work for credit.) 12. In another experiment, the mass of a hydrate was found to be 2.7090 grams. After heating, the anhydrous sample had a mass of 1.8820 grams. Answer the following and show all work for credit a. What was the mass of water lost? b. How many moles of water were lost? (Convert mass to moles.) c. The ionic compound was found to be calcium nitrate. How many moles of calcium nitrate are contained in the anhydrous samplo? (Convert mass to molos.) d. What is the ratio of moles of water to moles of anhydrous calcium nitrate? (Nearest Whole Numbers) Moles water Moles anhydrous calolum nitrate Q. What is the formula for this compound? (Hint: Have you soon this compound before? Think coefficients!)