Candle Lab
Name: ________________________________ Date: ___________
Purpose: To review stoichiometry and observe the effect of a limiting reactant
Materials: 1 candle, 1 watch glass, 1 250 ml beaker, matches, balance
Procedure:
1. Record the mass of your watch glass in the data table provided.
2. Light your candle, drip a little wax on to the watch glass and stick the candle to
the plate. Blow out the candle.
3. Record the total mass of the candle + watch glass.
4. Light the candle and allow the candle to burn until approximately 1 cm of the
candle remains. DO NOT TOUCH ANY OF THE MELTED WAX!
5. Record the mass of the candle and plate, including all of the melted wax.
6. Light your candle again, and then place an inverted beaker over the candle.
Record observations below, including approximately how long it took for the
candle to burn out.
Observations:
Data:
Mass of watch glass:
grams
Mass of candle + watch glass
grams
Mass of candle + watch glass + wax:
grams
Calculations:
1. What is the mass of the unburned candle?
2. What is the mass of the wax (unburned and melted) left over after burning?
3. How many grams of wax were completely burned? (The difference between the
starting mass in #1, and the ending mass in # 2.)
4. The equation for the burning of wax is:
C25H22 +
O2 
CO2 +
H2O
a. Balance the equation
b. Calculate the formula mass of wax.
c. How many moles of wax were in the candle before it burned? (Hint – use
the mass of the unburned candle as your given mass.)
d. How many moles of wax were chemically converted in to products? (Hint –
use the mass of wax completely burned as your given mass.)
5. How many grams of candle wax would you need to burn in order to obtain 2
grams of water?
a. Convert 2 g of water to moles
b. Use the mole ratios from your balanced equation above to determine how
many moles of candle wax must be used to produce this many moles of
water.
c. Convert your moles of candle wax to grams of candle wax, using the
formula for candle wax given above.
Conclusion Questions:
1. What are the reactants in the candle burning reaction?
2. How did the length of time that the candle burned in the room compare to the
length of time that it burned under the beaker?
3. When you put the beaker on the burning candle, which reactant became the
limiting one? How did you know?