In an experiment using a simple tin calorimeter 18.95g of methanol was burned to raise the temperature of 708g of water by 29.5 degrees celsius. Using this evidence, calculate the molar enthalpy of combustion of methanol (to produce water as a vapor).
To calculate the molar enthalpy of combustion of methanol, we need to use the following equation:
q = m * c * ΔT
where:
q = heat transferred in Joules
m = mass of the substance (water) in grams
c = specific heat capacity of the substance (water) in J/g °C
ΔT = change in temperature in °C
First, let's calculate the heat transferred to the water using the given information:
q = 708g * 4.18 J/g °C * 29.5 °C
q = 69953.8 J
Next, we need to convert the mass of methanol burned (18.95g) to moles of methanol. The molar mass of methanol (CH3OH) is 32.04 g/mol.
moles of methanol = 18.95g / 32.04 g/mol
moles of methanol = 0.59 mol
Now, we can calculate the molar enthalpy of combustion using the equation:
ΔH = q / moles of methanol
ΔH = 69953.8 J / 0.59 mol
ΔH = 118559.0 J/mol
Thus, the molar enthalpy of combustion of methanol (to produce water as a vapor) is approximately 118559 J/mol.
To calculate the molar enthalpy of combustion of methanol (to produce water as a vapor), we can use the following steps:
Step 1: Calculate the heat absorbed by the water.
The heat absorbed by the water can be calculated using the formula:
q_water = m_water * C_water * ΔT
Where:
q_water = heat absorbed by water (in Joules)
m_water = mass of water (in grams)
C_water = specific heat capacity of water (4.18 J/g°C)
ΔT = change in temperature of water (in °C)
Given:
m_water = 708g
C_water = 4.18 J/g°C
ΔT = 29.5°C
Substituting the values into the formula:
q_water = 708g * 4.18 J/g°C * 29.5°C
q_water = 708g * 4.18 J/°C * 29.5°C
q_water = 71,665.52 J
Step 2: Calculate the moles of methanol burned.
To calculate the moles of methanol burned, we can use the formula:
moles_methanol = mass_methanol / molar_mass_methanol
Given:
mass_methanol = 18.95g
molar_mass_methanol = 32.04 g/mol
Substituting the values into the formula:
moles_methanol = 18.95g / 32.04 g/mol
moles_methanol = 0.5919 mol
Step 3: Calculate the molar enthalpy of combustion.
The molar enthalpy of combustion can be calculated using the formula:
ΔH_combustion = q_water / moles_methanol
Given:
q_water = 71,665.52 J
moles_methanol = 0.5919 mol
Substituting the values into the formula:
ΔH_combustion = 71,665.52 J / 0.5919 mol
ΔH_combustion = 121,050 J/mol
Therefore, the molar enthalpy of combustion of methanol (to produce water as a vapor) is 121,050 J/mol.
To calculate the molar enthalpy of combustion of methanol (to produce water as a vapor), we need to use the following equation:
ΔH = q / n
Where:
ΔH = molar enthalpy of combustion in kJ/mol
q = heat transfer in Joules
n = number of moles of methanol
First, let's find the heat transfer (q) using the equation:
q = m * c * ΔT
Where:
m = mass of water in grams
c = specific heat capacity of water (4.18 J/g°C)
ΔT = change in temperature of water
In this case, the mass of water (m) is 708g, and the change in temperature (ΔT) is 29.5°C.
q = 708g * 4.18 J/g°C * 29.5°C
Calculate the value of q.
Next, we need to find the number of moles (n) of methanol using its molar mass.
The molar mass of methanol (CH3OH) is:
C = 12.01 g/mol
H = 1.01 g/mol
O = 16.00 g/mol
Calculate the molar mass of methanol and convert the mass given (18.95g) into moles by dividing the mass by its molar mass.
Now that we have obtained the values of q and n, we can substitute them into the equation to calculate the molar enthalpy of combustion (ΔH).
ΔH = q / n
Calculate the value of ΔH. This will give you the molar enthalpy of combustion of methanol to produce water as a vapor.