A quantity of 1.435g of naphthalene (C1oHs), a pungent-smelling substance used in moth repellents, was burned in a bomb calorimeter (constant volume). Consequently, the temperature of the water rose from 20.17°C to 25.84°C. If the mass of the water surrounding the calorimeter was exactly 2000g and the heat capacity of the bomb calorimeter was 1.80 KJ/°C, calculate the heat of combustion of naphthalene on a molar basis (molar heat of combustion), i.e. KJ/mol naphthalene. CH20 4.184 /g.°C
Why did the naphthalene go to the party? Because it wanted to make everyone moth-ivated! Now, let's calculate the molar heat of combustion.
First, we need to calculate the amount of heat released by the naphthalene during combustion. We can use the formula:
q = mcΔT
where q is the heat transferred, m is the mass, c is the specific heat capacity, and ΔT is the change in temperature.
The heat transferred to the water can be calculated as follows:
q_water = mc_waterΔT_water
Substituting the values:
q_water = 2000g * 4.184 J/g.°C * (25.84°C - 20.17°C)
Now, we need to convert this heat into kilojoules:
q_water = (2000g * 4.184 J/g.°C * (25.84°C - 20.17°C)) / 1000
Next, we need to calculate the heat released by the bomb calorimeter:
q_bomb_calorimeter = c_bomb_calorimeter * ΔT_bomb_calorimeter
Substituting the values:
q_bomb_calorimeter = 1.80 kJ/°C * (25.84°C - 20.17°C)
Now, we can calculate the total heat released during the combustion:
q_total = q_water + q_bomb_calorimeter
Finally, we can calculate the heat of combustion on a molar basis:
mol_naphthalene = 1.435g / 128.18 g/mol (molar mass of naphthalene)
molar_hoc = q_total / mol_naphthalene
I hope this calculation ignited a spark of curiosity in you!
To calculate the molar heat of combustion of naphthalene, we can use the equation:
q = mcΔT
Where:
q = heat absorbed or released (in this case, released)
m = mass of the substance (in this case, naphthalene)
c = specific heat capacity of water (4.184 J/g·°C)
ΔT = change in temperature of the water (final temperature - initial temperature)
First, let's convert the mass of naphthalene to moles. The molar mass of naphthalene (C10H8) is 128.16 g/mol.
Mass of naphthalene = 1.435 g
Moles of naphthalene = mass of naphthalene / molar mass = 1.435 g / 128.16 g/mol
Next, calculate the heat released by the naphthalene using the formula:
q = mcΔT
where:
m = mass of the water = 2000 g
c = specific heat capacity of water = 4.184 J/g·°C
ΔT = change in temperature = 25.84°C - 20.17°C
Convert ΔT to Kelvin:
ΔT = 25.84°C - 20.17°C = 5.67°C
ΔT(K) = 5.67°C + 273.15 = 278.82 K
Now substitute the values into the formula:
q = (2000 g) * (4.184 J/g·°C) * (278.82 K)
Next, convert the heat from Joules to kilojoules:
q (kJ) = q (J) / 1000
Finally, calculate the molar heat of combustion:
Molar heat of combustion = q (kJ) / Moles of naphthalene
Now you can follow the steps to calculate the molar heat of combustion using the given values.
To calculate the molar heat of combustion of naphthalene (C10H8), we need to use the following steps:
Step 1: Calculate the heat absorbed by the water:
We know that the heat absorbed by the water is given by the formula: q = mcΔT, where q is the heat absorbed, m is the mass of the water, c is the specific heat capacity of water, and ΔT is the change in temperature.
Given:
m = 2000 g (mass of water)
c = 4.184 J/g°C (specific heat capacity of water)
ΔT = 25.84°C - 20.17°C = 5.67°C
Substituting these values into the formula, we get:
q = (2000 g) * (4.184 J/g°C) * (5.67°C)
q = 47526.56 J
Step 2: Convert the heat absorbed to kilojoules:
Since the heat capacity of the bomb calorimeter is given in kilojoules, we need to convert the heat absorbed to kilojoules by dividing by 1000.
q = 47526.56 J / 1000
q = 47.52656 kJ
Step 3: Calculate the heat of combustion of naphthalene:
The heat of combustion is the heat released or absorbed when one mole of a substance undergoes complete combustion. In this case, we burned 1.435 g of naphthalene.
To calculate the molar heat of combustion, we need to determine the number of moles of naphthalene burned. This can be done using the molar mass of naphthalene (C10H8), which is given by the atomic masses of each element in the molecule.
Molar mass of naphthalene (C10H8) = (10 * atomic mass of carbon) + (8 * atomic mass of hydrogen)
Atomic mass of carbon = 12.01 g/mol
Atomic mass of hydrogen = 1.01 g/mol
Molar mass of naphthalene = (10 * 12.01 g/mol) + (8 * 1.01 g/mol) = 128.18 g/mol
To calculate the number of moles of naphthalene:
moles = mass / molar mass = 1.435 g / 128.18 g/mol ≈ 0.01118 mol
Finally, to calculate the molar heat of combustion, we divide the heat of combustion by the number of moles of naphthalene burned:
Molar heat of combustion = (heat of combustion) / (moles of naphthalene burned)
Molar heat of combustion = 47.52656 kJ / 0.01118 mol ≈ 4259.82 kJ/mol
Therefore, the molar heat of combustion of naphthalene is approximately 4259.82 kJ/mol.
heat given off is q = mass x specific heat H2O x (Tfinal-Tinitial)
Calculate q (in J). Then
qtotal = qnaph + qcal
You know qtotal. You want qnaph. qcal = [1.80 kJ/C *(Tfinal-Tinitial)]. Change to J from kJ.
Solve for qnaph and that will be in J. Convert to kJ and that will be for 1.435 g, Convert to kJ/mol and you have it. Note C10Hs is a typo.