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Plan & Design: the Relationship Between Relative Atomic Mass and Heat of Combustion for C2 to C5 in Straight Chain Alcohols.

• Date Submitted: 10/26/2010 03:12 PM
• Flesch-Kincaid Score: 55.6
• Words: 515
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STATEMENT: Alcohols are liquid fuels with energy values (ΔHc) that are related to their relative molecular mass (Mr).   Plan and design an experiment that would allow you to establish the relationship between Mr and ΔHc value for C2 to C5 straight chain alcohols.
HYPOTHESIS: As Mr increases (number of carbon atoms per molecule) in straight chain alcohols from C2 to C5, the heat of combustion increases (ΔHc decreases).
APPARATUS + MATERIALS: 400cm3 water; 50cm3 each of: ethanol, propanol, butanol, pentanol; thermometer; 50cm3 spirit lamp; 100cm3 measuring cylinder; 250cm3 beaker; tripod stand; wire gauze; electronic scale; matches
METHOD: Fill the spirit lamp with 50cm3 ethanol. Weigh the lamp with contents included. Record this value. Set up the apparatus as shown below, using 100cm3 of water (measure using the measuring cylinder). Record the temperature of the water. Light the wick and let the flame light until the temperature of the water has risen by 35oC. Note the new temperature of the water. Extinguish the flame. Re-weigh the spirit lamp including its contents. Record this value.
Repeat these steps, instead using propanol, then butanol, and then finally pentanol.

VARIABLES:
* Control- volume of each alcohol used (50cm3), temperature rise of water (35oC), volume of water used (100cm3)
* Manipulated-type of alcohol used (number of carbon atoms per molecule of alcohol)
* Responding-mass of lamp and contents after heating
CALCULATIONS:
ALCOHOL | MASS OF LAMP WITH CONTENTS/g | TEMPERATURE OF WATER/oC |
NAME | FORMULA | RELATIVE MOLECULAR MASS, Mr | BEFORE HEATING | AFTER HEATING | MASS BURNED | AFTER HEATING | BEFORE HEATING | TEMPERATURE RISE |
Ethanol | C2H5OH | 46 | | | | | | |
Propanol | C3H7OH | 60 | | | | | | |
Butanol | C4H9OH | 74 | | | | | | |
Pentanol | C5H11OH | 88 | | | | | | |
For Ethanol:
Molar mass = (relative molecular mass)g = 46g
Mass of ethanol burned = _a_ g = x46 moles = _b_ moles of...