3.09: Molar Mass of Compounds
Purpose: Determining the Empirical Formula of a Tin Oxide
Record the contents of the evaporating dish in the data table below.
Item
Mass, grams
Evaporating Dish
19.508 G
Evaporating Dish and two scoops of Tin
20.609 G
Evaporating dish, Tin, and Nitric acid (before
20.609 G
heating)
Evaporating dish and compound (after heating)
20.212 G
Observations
Before the compound was heated the color was
blue after it was heated the compound was
white.
Answer the following questions in your notebook so that you have them available when you take
the quiz for this lesson.
1) The mass of tin in the evaporating dish remained constant throughout the experiment.
This means that the mass change that any additional mass in the evaporating dish after
the reaction is from the oxygen that bonded with the tin. Subtract the mass of the tin and
dish from the mass of the compound and dish to determine the mass of the oxygen.
Mass of oxygen = mass of Dish and compound – mass of Dish and Tin
Mass of oxygen = 20.609 G – 20.212 G
Mass of oxygen = 0.397
2) Solve for the mass of tin in the dish by subtracting the mass of the clean, empty dish in
Step 1 from the mass of the tin and dish in Step 2.
Mass of tin = mass of Dish and Tin – Mass of Dish
Mass of tin = 20.609 G – 19.508 G
Mass of tin = 1.101 G
3) Use the mass values of each element to determine the empirical formula of the tin oxide
compound.
Convert the mass of tin to moles of tin.
0.173 g/mol
Convert the mass of oxygen to moles of oxygen.
0.003 g/mol
Divide by the lowest mole value to get a whole number mole ratio.
What is the formula for the hydrate?
Because this is the empirical formula of an ionic compound, the empirical formula is also the
formula unit. What is the full name (including Roman numeral) of this compound?