1.20 g of hydrogen gas is completely burned in the presence of excess oxygen gas in a bomb calorimeter producing water. The heat capacity of the calorimeter is 9.43 kJ/°C and the temperature of the calorimeter rose from 25.55 °C to 41.97°C. Calculate the enthalpy change in J and in kJ/mol or water produced.
m=120g
c= 9.43
T1= 25.55 C
T2= 41.97 C
I don't know what to do after this
2H2 + O2 ==> 2H2O
mols H2 gas initially = 1.20/4 = 0.3 and since the ratio of H2O produced to mols H2 initially is 2/2 we must have produced 0.3 mols H2O.
q = heat capacity x (Tfinal-Tinitial) = ? kJ = dH rxn.
So dH rxn in kJ is for 0.3 mol H2O produced so dH rxn/0.3 gives you dH rxn in kJ/1 mol. Then convert to J also.
Post your work if you get stuck.
n=m/M = 1.2/4 =0.3 mols
q=ct = (9.43)(16.42)
I am stuck here
To calculate the enthalpy change in joules (ΔH) for the reaction, you can use the formula:
ΔH = q / n
where:
q = heat absorbed or released in joules by the reaction
n = number of moles of the substance undergoing the reaction
Here's how you can proceed:
1. Determine the heat absorbed or released (q) by the reaction using the equation:
q = m * c * ΔT
where:
m = mass of the substance undergoing the reaction (in grams)
c = heat capacity of the calorimeter (in joules per degree Celsius per gram)
ΔT = change in temperature (final temperature - initial temperature) in degrees Celsius
In this case, you have:
m = 1.20 g
c = 9.43 kJ/°C = 9430 J/°C (since 1 kJ = 1000 J)
ΔT = (41.97 - 25.55) °C = 16.42 °C
Substituting the values:
q = 1.20 g * 9430 J/°C * 16.42 °C
2. Convert the mass of the substance undergoing the reaction (in grams) to moles by using the molar mass of hydrogen gas (H2), which is 2 g/mol.
mol = mass / molar mass
mol = 1.20 g / 2 g/mol
3. Calculate the enthalpy change (ΔH) in joules by dividing q by the number of moles (n):
ΔH = q / n
Substitute the values:
ΔH = (1.20 g * 9430 J/°C * 16.42 °C) / (1.20 g / 2 g/mol)
You should obtain the ΔH value in joules.
4. If you want to convert the ΔH value to kilojoules per mole of water produced, divide the ΔH value by the molar mass of water (H2O), which is 18 g/mol:
ΔH in kJ/mol = ΔH in J / molar mass of water
Substitute the values and convert the units as necessary.
Following these steps, you should be able to calculate both the enthalpy change in joules and in kJ/mol of water produced.