Molar Mass of Butane Lab Period: 1B 10/12/2020 Objective: To determine the Molar Mass of Butane Materials: ● Butane Lighter ● 250mL Erlenmeyer Flask ● Plastic Slide ● 100mL Graduated cylinder ● 2L Beaker ● Distilled water ● Balance Pan ● Thermometer ● Goggles Procedure: 1. Wear safety goggles 2. Measure the mass of the lighter on the balance pan and record the volume of the lighter. 3. Measure the temperature of the distilled water and make sure its room temperature. 4. Using a 100mL graduated cylinder, fill the Erlenmeyer flask all the way to the top with the water and then record the total volume of the Erlenmeyer flask. 5. Cover the Erlenmeyer flask with the plastic slide, ensuring no air gets inside, and flip the flask over into the 2L beaker (which contains room temperature distilled water) then remove the plastic slide, keeping the flask submerged upside down in the water. 6. Light the butane lighter underneath the Erlenmeyer Flask, so the bubbles from the lighter go inside the opening of the flask. 7. Keep the lighter lit under the opening of the Erlenmeyer flask until the amount of gas in the flask is equal to 200mL. Use the lines on the flask to estimate the volume of gas. 8. Line up the level of water in the flask with the water level in the beaker. 9. Put plastic over the flask, and flip it back out of the beaker, making sure not to spill water. 10. Measure the remaining water in the Erlenmeyer flask. 11. Dry off the lighter and wait at least a day for it to become completely dry. After it is completely dry, measure the new mass of the butane lighter. Safety Precautions: ● Wear goggles Data: Initial Mass of Butane Lighter: 12.99g Final Mass of Butane Lighter: 12.44g Mass of the Butane: 0.55g Initial temperature of Water: 23°C Initial Volume of Water in Flask: 285mL Final Volume of Water in Flask: 66mL Final Volume of Butane: 219mL Barometric Pressure: 30.02in Hg Calculations: Conclusion: The results were relatively accurate because the calculated percent error is 7.54%. The molar mass of butane was calculated to be 62.5 grams. The possible reason for a 7.54% percent error is because of human error. Questions: 1. A student used cold tap water for this experiment instead of water that was equilibrated to room temperature. Assuming all other aspects of the lab were perfect would the results be lower or higher than theory? Justify your answer The results of the lab would be higher because if a smaller number was plugged into the ideal gas law during calculations, then this would result in a larger number in the denominator when the R and T values are multiplied. Since a smaller number is in the denominator, this would result in a bigger number since a smaller number in the denominator is going into a larger one. 2. A student assumed the Erlenmeyer flask held 250 ml of water instead of measuring the volume. Assuming all other aspects of the lab were perfect would the results be lower or higher than theory? Justify your answer The results would be much lower because the flask held more water than then the student assumed. If the amount of water left in the flask stays the same, then the calculated volume of the butane would be lower, which would then affect the calculated molar mass 3. A student did not include the vapor pressure of water in their calculations. Assuming all other aspects of the lab were perfect would the results be lower or higher than theory? Justify your answer If the student did not include the vapor pressure of water in their calculations, then the molar mass yielded would be lower and the percent error would be higher because when you use the total atmospheric pressure in the PV=nRT equation, instead of the total pressure minus the vapor pressure, it will yield a larger number of moles. Then, when calculating the molar mass, it would divide the mass of butane up by a greater number, which would result in a smaller molar mass. 4. A student did not line up the water level in the flask with the water level in the larger water tank. The water line in the flask was far above the water line in the tank. Assuming all other aspects of the lab were perfect would the results be lower or higher than theory? Justify your answer The results of the lab would be higher because if the water level of the flask was not aligned with the water level of the larger water tank, then the gases in the flask would be added to the volume of butane, which would increase the volume of butane. 5. A student did not thoroughly dry the lighter before determining the second mass. Assuming all other aspects of the lab were perfect would the results be lower or higher than theory? Justify your answer The results would be higher because the lighter was not thoroughly dried before determining the second mass. If the lighter had water left inside of it, then the mass of the water would add to the total of the second mass, so then the second total mass would be higher than the theoretical because an outside mass of water was added to it.