2. Predict the approximate amount of heat liberated by burning a gram of candle wax and a gram of propyl alcohol (Note: candle wax is a mixture of saturated carbon compounds with 20 or more carbons in each molecule and no oxygen. Propyl alcohol has the formula C3H7OH.) If time permits. perform an experiment to check your prediction.
You can estimate the heat of combustion for these two by using the delta Hfomation tables but it may be difficult to find data for candle wax. For propyl alcohol,
C3H7OH + 9/2 O2 ==> 3CO2 + 4H2O
delta Hrxn = (3*delta Hf CO2 + 4*dela Hf H2O) - (dela Hf C3H7OH).
WTH did DrBob22 just say?
To predict the approximate amount of heat liberated by burning a gram of candle wax and a gram of propyl alcohol, we can make use of the concept of calorimetry. Calorimetry is the measurement of heat transfer during a chemical reaction, and it can help us calculate the amount of heat released or absorbed.
To find the heat liberated, we need to determine the enthalpy of combustion for candle wax and propyl alcohol. The enthalpy of combustion is the heat energy released when one mole of a substance undergoes complete combustion with oxygen.
Here's how you can predict the approximate amount of heat liberated:
1. Determine the balanced chemical equation for the combustion of candle wax and propyl alcohol with oxygen. The balanced equation for candle wax can be assumed as a general hydrocarbon with the formula CnH2n+2. For propyl alcohol (C3H7OH), the balanced equation is:
C3H7OH + 4.5O2 -> 3CO2 + 4H2O
2. Find the molar mass of candle wax and propyl alcohol. The molar mass of wax can vary depending on the specific type, but for approximation, you can assume it to be around 300 g/mol. The molar mass of propyl alcohol is approximately 60 g/mol.
3. Calculate the moles of candle wax and propyl alcohol. Divide the mass of each substance by its molar mass. For a gram of each substance, you will have:
Moles of candle wax = 1 g / 300 g/mol
Moles of propyl alcohol = 1 g / 60 g/mol
4. Use the balanced chemical equations to determine the heat of combustion for each substance. The molar coefficient in the balanced equation indicates the ratio of moles of the substance to moles of combustion products. The enthalpy change will be per mole of substance.
For candle wax, the enthalpy of combustion will be given by ΔH = x kJ/mol
For propyl alcohol, the enthalpy of combustion will be given by ΔH = y kJ/mol
5. Calculate the approximate amount of heat liberated by multiplying the enthalpy change (ΔH) by the number of moles:
Heat liberated by burning candle wax = ΔH * Moles of candle wax
Heat liberated by burning propyl alcohol = ΔH * Moles of propyl alcohol
Performing an experiment to check the prediction requires a calorimeter setup to measure the heat released during combustion. Care should be taken to ensure safety protocols are followed, such as performing the experiment in a well-ventilated area and using appropriate safety equipment.
By following these steps, you can predict the approximate amount of heat liberated by burning a gram of candle wax and propyl alcohol, and also perform an experiment to verify your prediction.