OpiumChem: January 2014

Thursday, January 23, 2014

Empirical Formula Lab

Purpose:

Find the Empirical Formula for Magnesium Oxide.

Procedure:

1. After cleaning and drying crucible, weigh it and record the result.

2. Crumple up 2 inches of Magnesium ribbon, place it in the crucible and weigh it. Record the result.

3. Heat magnesium in crucible until it is completely burnt.

4. Once cool, weight the crucible again and record the mass.

Data:

Mass of crucible: 19.5656g

Initial mass of crucible with magnesium: 19.7415g

Mass of magnesium: .1759g

Mass of crucible after burning:19.8494g

Mass of Oxygen: .1079g

Calculations:

.1759g(1mol/24g)=.00733mol magnesium

.1079g(1mol/16)=.00674mol Oxygen

.00733mol/.00674mol=1.09

(1-1.09)/1=.09% error

Conclusion:

After burning a hunk of magnesium, magnesium oxide was formed. By weighing and calculating the masses of each oxygen and magnesium were found, and there was a .09% error made in calculating the empirical formula. The ratio should have been one to one, but in the experiment an erro in weighing or duration of burning was made and got a ratio of one to one point nine.

Monday, January 13, 2014

Percent Composition Lab

Purpose: To measure the percent of water in a series of crystalline compounds called hydrates.

Procedure:

1) Label each test tube with the name of the compound. Measure and record the masses.

2) Add 2-3 grams of each compound to the appropriate tube. Measure and record the mass of each test tube and compound.

3) Heat contents of test tubes over Bunsen burner, holding at 45 degree angle. Not any changes in appearance.

4) Heat from 2-4 minutes. Repeat steps 2 and 3 twice.

5) Allow each tube to cool, then measure and record the mass of each test tube and heated compound.

Data:

Calculations:

9.38g-7.58g=1.8g. (.18g/1.8g)x100=10% water

9.69g-7.56g=2.13g. (.58g/2.13g)x100=27.23% water

9.21g-7.58g=1.63g. (.52g/1.63g)x100=32.9% water

Calculations Check:

Conclusion:

In this lab the percentage of water in compounds were found by indirectly with use of evaporation and some calculations. To check the answers, mole conversions were used to find the empirical formula for each compound. The results were fairly reasonable and accurate, and other than human error, few errors were identifiable in this lab. Some generalities in rounding to arrive at the empirical formulas could also have contributed to inaccuracy in the answers.