I got 0.907 KJ for ΔHcomb but I don't know if its correct. I also don't know how to write the equation.
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question:
A calorimeter is filled with 10.0 mole of methane gas and an excess of oxygen. When burned, the ignition wire releases 107.2 J of heat. The heat capacity of the calorimeter (including the bomb and water) is 4.319 kJ oC-1.
The initial temperature is 24.75 degrees celsius and the final temperature is 26.85 degrees celsius
Calculate ΔHcomb for methane and determine the thermochemical reaction?
I assume your 0.907 is from
4.319kJ/C x (2.1C) = 9.07 kJ/10 mol = 0.907 kJ/mol. But you must correct for the wire and I don't think you've done that.
The equation is
CH4 + 2O2 ==> CO2 + 2H2O + heat
When they say thermochemical reaction they may want dH = -? since it is exothermic.
I looked up the value of delta H combustion for CH4 and found about 890 kJ/mol Check those numbers.
Also I found on the web a tutorial in which all of these numbers were the same as your post EXCEPT the 10.0 mols was 10.0 millimoles. Using 10.0 mmols would make the answer come out about right.
To calculate ΔHcomb (the heat of combustion) for methane and determine the thermochemical reaction, you need to use the information provided in the question.
First, let's write the balanced chemical equation for the combustion of methane:
CH4 + 2O2 -> CO2 + 2H2O
Here's how you can calculate ΔHcomb:
Step 1: Calculate the heat released by the ignition wire.
Given that the ignition wire released 107.2 J of heat, convert it to kilojoules (kJ) by dividing by 1000:
107.2 J ÷ 1000 = 0.1072 kJ
Step 2: Calculate the total heat absorbed by the calorimeter.
The total heat absorbed by the calorimeter is the sum of the heat released by the methane combustion and the heat released by the ignition wire. Let's call this total heat Q.
Q = heat released by methane combustion + heat released by ignition wire
Since the heat released by the ignition wire is known (0.1072 kJ), we need to determine the heat released by the methane combustion.
Step 3: Determine the heat released by the methane combustion.
To do this, you will use the heat capacity of the calorimeter, the initial temperature, and the final temperature.
ΔT = final temperature - initial temperature = 26.85 °C - 24.75 °C = 2.1 °C
Convert ΔT to Kelvin:
ΔT = 2.1 °C + 273.15 = 275.25 K
Now calculate the heat released by the methane combustion using the formula:
ΔHcomb = Q/moles of methane
Given that the moles of methane are 10.0 moles and the heat capacity of the calorimeter is 4.319 kJ °C^-1:
Q = 4.319 kJ °C^-1 * ΔT
Q = 4.319 kJ °C^-1 * 275.25 K
Now calculate ΔHcomb by dividing Q by the moles of methane:
ΔHcomb = Q / moles of methane = (4.319 kJ °C^-1 * 275.25 K) / 10.0 moles
Step 4: Calculate ΔHcomb.
Now substitute the values into the equation to find ΔHcomb:
ΔHcomb = (4.319 kJ °C^-1 * 275.25 K) / 10.0 moles
Calculate this to find the value of ΔHcomb.
In your calculation, you mentioned getting 0.907 kJ for ΔHcomb. Double-check your calculations to confirm if it is correct.
Once you have obtained the value for ΔHcomb, you can interpret it to determine the thermochemical reaction. In this case, since methane (CH4) is being burned with oxygen (O2), the thermochemical reaction is the combustion of methane to produce carbon dioxide (CO2) and water (H2O).