Burning Candle Investigation

Background

Have you ever wondered if that expensive candle you bought would really burn as many hours as the label claimed? In this investigation, you will calculate the amount of moles that will burn in 8 minutes. You will practice finding the amount of molecules in the candle that you burn for 8 minutes. Avogadro’s number is 6.022 × 1023 atoms or molecules are equal to 1 mole of the element or compound you are investigating. You must also remember that 1 mole is = to the molar mass of the element or compound. The chemical formula for candle wax is C25H52.

KNOW: What do you know about molar calculations?

Objectives

-Calculate the molar mass of candle wax.

-Perform stoichiometry calculations involving mass, moles, and molecules.

-Calculate the time to burn one mole of candle wax.

Materials

Goggles, matches, candle, glass plate, stopwatch

Procedure

1. Weigh a glass plate

2. Weigh the candle BEFORE burning

3. Place the candle on the glass plate and burn the candle for 8 minutes.

DO NOT TOUCH THE MELTED WAX OR YOUR CALCULATIONS WILL BE INCORRECT.

Make sure to let your candle burn on the glass plate so no product is lost during the reaction.

4. Blow out the candle, and measure the mass of the candle and the glass plate(we want the mass of any dripped wax which is why we use the plate)

5. Subtract the glass plate and calculate the mass of the candle again.

6. Subtract the candle after burning from the candle before burning to find the mass of the wax burned.

Data

Mass plate / Mass candle before burning / Mass candle after burning / Mass burned wax

1.Calculate the molar mass of candle wax. You will need to add the masses up using the periodic table. Remember that candle wax is C25H52. This means you will need to add up the masses of 25 carbon atoms and 52 hydrogen atoms.

2. Calculate the number of moles of the candle before it burned:

___g candle before burning × 1 mole= ______moles candle

g(molar mass of candle wax)

3. Calculate the number of molecules of the unlit candle.(use your answer from #2 for the moles of the candle)

___moles candle × (6.022 × 1023 molecules)=_____molecules

1mol

4. Calculate the number of moles of the wax burned.

___g wax burned × 1 mol=____moles burned

g(molar mass of candle)

5. Calculate the number of molecules of wax burned. Use your moles from #4 of wax burned.

___moles wax burned × (6.022 × 1023 molecules) = _____molecules burned

1mole

6. Calculate the amount of time it will take to burn 1 mole of candle wax (remember to solve by cross multiplying because this is a proporation)

g burned wax = molar mass of candle wax

time burned x(time to burn 1 mole of candle)

WHAT: What did you learn about molar calculations?

Answer two analysis questions with complete sentences.

1. What are the two conversions factors in this lab? You do not need to use complete sentences on this question.

2. Describe the process to find the molar mass of a compound.

3. Why did you weigh the candle on the glass plate?

LEARN: What do you still want to learn about molar calculations?