Respuesta :
Answer: The enthalpy of the reaction is -1056.44 kJ
Explanation:
To calculate the heat absorbed by the calorimeter, we use the equation:
[tex]q=c\Delta T[/tex]
where,
q = heat absorbed
c = heat capacity of calorimeter = 9.49 kJ/°C
[tex]\Delta T[/tex] = change in temperature = 4.32°C
Putting values in above equation, we get:
[tex]q=9.49kJ/^oC\times 4.32^oC=40.99kJ[/tex]
Heat absorbed by the calorimeter will be equal to the heat released by the reaction.
Sign convention of heat:
When heat is absorbed, the sign of heat is taken to be positive and when heat is released, the sign of heat is taken to be negative.
To calculate the number of moles, we use the equation:
[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex]
Given mass of ethanol = 1.785 g
Molar mass of ethanol = 46 g/mol
Putting values in above equation, we get:
[tex]\text{Moles of ethanol}=\frac{1.785g}{46g/mol}=0.0388mol[/tex]
To calculate the enthalpy change of the reaction, we use the equation:
[tex]\Delta H_{rxn}=\frac{q}{n}[/tex]
where,
q = amount of heat released = -40.99 kJ
n = number of moles of ethanol = 0.0388 moles
[tex]\Delta H_{rxn}[/tex] = enthalpy change of the reaction
Putting values in above equation, we get:
[tex]\Delta H_{rxn}=\frac{-40.99kJ}{0.0388mol}=-1056.44kJ/mol[/tex]
Hence, the enthalpy of the reaction is -1056.44 kJ
The molar heat combustion of the ethanol, CH₃CH₂OH is –1056.62 KJ/mol
We'll begin by calculating the heat absorbed by the calorimeter. This can be obtained as follow:
Heat capacity (C) = 9.49 KJ/C
Change in temperature (ΔT) = 4.32 °C
Heat absorbed (Q) =?
Q = CΔT
Q = 9.49 × 4.32
Q = 40.9968 KJ
- Next, we shall determine the number of mole in 1.785 g of ethanol, CH₃CH₂OH. This can be obtained as follow:
Mass of CH₃CH₂OH = 1.785 g
Molar mass of CH₃CH₂OH = 12 + (3×1) + 12 + (2×1) + 16 + 1 = 46 g/mol
Mole of CH₃CH₂OH =?
Mole = mass / molar mass
Mole of CH₃CH₂OH = 1.785 / 46
Mole of CH₃CH₂OH = 0.0388 mole
- Finally, we shall determine the molar heat combustion of ethanol. This can be obtained as follow:
Heat absorbed by calorimeter = heat released by ethanol
Heat absorbed (Q) = 40.9968 KJ
Heat released (Q) = –40.9968 KJ
Number of mole (n) = 0.0388 mole
Enthalpy of reaction (ΔH) =?
Q = n•ΔH
–40.9968 = 0.0388 × ΔH
Divide both side by 0.0388
ΔH = –40.9968 / 0.0388
ΔH = –1056.62 KJ/mol
Therefore, the molar heat combustion of the ethanol, CH₃CH₂OH is –1056.62 KJ/mol
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