Enthalpy of combustion of alcohols C0095

Summary

This video explains an experiment measuring the enthalpy of combustion of five alcohols: methanol, ethanol, propanol, butanol, and pentanol. Water is heated using each alcohol, with the temperature rise and mass of the burner recorded before and after combustion. The procedure is repeated for each alcohol, noting initial and final temperatures and masses. The results show how each alcohol affects water temperature and energy release during combustion, providing a comparison of their efficiencies. The experiment highlights the scientific method of investigating energy transfer in chemical reactions.

Takeaways

• 🔥 The experiment measures the enthalpy of combustion for five alcohols: methanol, ethanol, propanol, butanol, and pentanol.
• 💧 Each alcohol burner heats 120 cm³ of water in a copper calorimeter, and the initial and final masses of the alcohol burners are recorded.
• 🌡️ The initial temperature of the water is taken before the flame is lit, and the temperature rise is measured throughout the experiment.
• 🧪 Ethanol: Initial mass 193.83g, final mass 193.34g. The water's temperature increased from 26°C to 35.5°C.
• 🧪 Propanol: Initial mass 228.56g, final mass 228.14g. The water's temperature increased from 25°C to 35°C.
• 🧪 Butanol: Initial mass 222.12g, final mass 221.69g. The water's temperature increased from 25°C to 35.5°C.
• 🧪 Pentanol: Initial mass 215.68g, final mass 215.34g. The water's temperature increased from 25°C to 34.5°C.
• 🧪 Methanol: Initial mass 184.37g, final mass 183.72g. The water's temperature increased from 25.5°C to 34°C.
• 🔬 Stirring is performed throughout each experiment to ensure even heat distribution, but the efficiency of stirring varies.
• 📊 The maximum temperature reached during the experiment is used to calculate the enthalpy of combustion for each alcohol.

Q & A

What is the main purpose of the experiment described in the transcript?

The main purpose of the experiment is to measure the enthalpy of combustion of five alcohols (methanol, ethanol, propanol, butanol, and pentanol) by recording the temperature rise of water in copper calorimeters and the mass change of alcohol burners before and after heating.

How much water is used in each copper calorimeter?

Each copper calorimeter contains 120 cm³ of water.

What measurements are taken during the experiment?

The experiment involves measuring the mass of each alcohol burner before and after heating the water, and recording the temperature rise of the water using a thermometer.

What is the starting temperature of the water for the ethanol experiment?

The starting temperature of the water for the ethanol experiment is 26°C.

What is the final temperature of the water after heating with ethanol?

The final temperature of the water after heating with ethanol is 35.5°C.

What are the initial and final masses of the ethanol burner?

The initial mass of the ethanol burner is 193.83 grams, and the final mass is 193.34 grams.

How does the experimenter ensure that the thermometer readings are accurate?

The experimenter ensures the thermometer readings are accurate by making sure the thermometer is not touching the base of the calorimeter and by stirring the water continuously to distribute the heat evenly.

What is the initial mass of the propanol burner, and what temperature did the water reach?

The initial mass of the propanol burner is 228.56 grams, and the water reached a temperature of 35°C.

Which alcohol produced the highest final temperature during the experiment?

Both ethanol and butanol produced the highest final temperature of 35.5°C during the experiment.

What is the significance of weighing the alcohol burners before and after the experiment?

Weighing the alcohol burners before and after the experiment allows the experimenter to calculate the amount of alcohol consumed during combustion, which is necessary for determining the enthalpy of combustion.