A 4.98 g sample of aniline (C6H5NH2, molar mass = 93.13 g/mol) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ/°C. If the temperature rose from 29.5°C to 69.8°C, determine the value of ΔH°comb for aniline.
q = Cp*dT = 4.25 kJ/C x (69.8-29.5) = ?kJ and you need to assign the proper sign.
Then qaniline/g = ?kJ/4.98 and
q analine in kJ/mol = (?kJ/4.98) x (molar mass) = xx.
To determine the value of ΔH°comb (standard enthalpy of combustion) for aniline, we need to calculate the heat (q) released during the combustion reaction using the equation:
q = C × ΔT
where q is the heat released, C is the heat capacity of the calorimeter, and ΔT is the change in temperature.
In this case, the mass of aniline is 4.98 g and the molar mass is 93.13 g/mol. We can use these values to determine the number of moles of aniline combusted:
moles = mass / molar mass
moles = 4.98 g / 93.13 g/mol
Next, we need to calculate the heat (q) released during the combustion reaction:
q = C × ΔT
q = 4.25 kJ/°C × (69.8°C - 29.5°C)
Now, we need to convert the moles of aniline to kilojoules of heat:
ΔH°comb = q / moles
Substituting the known values:
ΔH°comb = q / (4.98 g / 93.13 g/mol)
Simplifying the calculation:
ΔH°comb = q × (93.13 g/mol) / 4.98 g
Now, let's calculate the value of ΔH°comb:
To calculate the value of ΔH°comb (standard heat of combustion) for aniline, you need to use the formula:
ΔH°comb = q / n
Where:
- ΔH°comb is the standard heat of combustion
- q is the heat energy released during combustion
- n is the number of moles of aniline combusted
To find the value of ΔH°comb, we need to find the heat energy released during combustion (q). We can calculate q using the formula:
q = C × ΔT
Where:
- q is the heat energy released during combustion
- C is the heat capacity of the bomb calorimeter
- ΔT is the change in temperature
First, let's calculate ΔT (change in temperature):
ΔT = TF - TI
= 69.8°C - 29.5°C
= 40.3°C
Next, let's convert ΔT from Celsius to Kelvin:
ΔT(K) = ΔT(°C) + 273.15
= 40.3°C + 273.15
= 313.45 K
Now we can calculate q (heat energy released during combustion) using the formula:
q = C × ΔT
Note that the heat capacity (C) needs to be converted from kJ/°C to J/K because the change in temperature is in Kelvin:
C(J/K) = C(kJ/°C) × 1000
= 4.25 kJ/°C × 1000
= 4250 J/K
Now we can calculate q:
q = C × ΔT
= 4250 J/K × 313.45 K
= 1,333,862.5 J
Next, we need to determine the number of moles of aniline (n) that was combusted. To do this, we can use the molar mass and mass of the aniline sample:
n = m / M
Where:
- n is the number of moles
- m is the mass of the aniline sample
- M is the molar mass of aniline
Given:
- Mass of aniline sample (m) = 4.98 g
- Molar mass of aniline (M) = 93.13 g/mol
n = m / M
= 4.98 g / 93.13 g/mol
= 0.0535 mol
Finally, we can calculate the value of ΔH°comb:
ΔH°comb = q / n
= 1,333,862.5 J / 0.0535 mol
= 24,954,205 J/mol
Therefore, the value of ΔH°comb for aniline is approximately 24,954,205 J/mol.