Determining the Number of Moles and Molecules Used up in a Burning Candle

DETERMINING THE NUMBER OF MOLES AND MOLECULES USED UP IN A BURNING CANDLE

1. Measure the mass of an index card and record in the data table. 2. Light a candle and drip a little wax on the card. Stick the candle to the wax and blow out the candle. Measure the mass and record on the data table. 3. Light the candle and allow it to burn 3 minutes. Do not play with the wax – this will affect your results. Blow out the candle. 4. Reweigh the candle and card without losing any melted wax and record in the data table. 5. Calculate the mass of the candle that has burned in 3 minutes and record.

Mass of index card (step 1) g Mass of candle + card (step 2) g Mass of candle without card (2-1) g Mass of candle and card after burning 3 minutes (step 4) g Mass of candle only after burning 3 minutes (4-1) g Mass of candle used up in burning g

CALCULATIONS

Wax is a mixture of hydrocarbons. C25H52 can be used as a representative hydrocarbon in the mixture. The burning of wax is shown below:

C25H52 + ______O2  ______CO2 + ______H2O + energy

a) Balance the equation above.

b) What is the molar mass of wax?

c) How many moles of wax were in the candle before it burned?

d) How many molecules are in the candle before it burned? e) How many moles of wax were used up during the burning?

f) How many molecules of wax were used up during the burning?

g) How long would it take to burn 1 mole of candle wax?

CONCLUSIONS:

1) What 2 resources are used up as a candle burns?

2) What has happened to the atoms in these resources?

3) Is it possible to recover these 2 resources after they’ve been used? Explain.