Search: How much energy (in Kj) is relased when 25.0g of ethanol vapor at 93, is cooled to -10? Ethanol has a melting point of -114.5, bp of 78.4, specific heat= 2.10J/g, heat of fusion =4.60Kj/mol, specicic heat= 1.9j/g, heat of vaporization = 38.56Kj/mol
Energy=(25.0g)(2.10J/g)(93+10)
Energy=5407.5 J*(1 KJ/ 1000 J)
Energy= 5.41 KJ
To calculate the amount of energy released when ethanol vapor is cooled from 93°C to -10°C, we need to consider different temperature ranges and phase changes involved. Here is the step-by-step process:
1. Calculate the energy released during the cooling of ethanol vapor from 93°C to its boiling point (78.4°C):
The formula to calculate the energy released during temperature change is:
Energy = mass × specific heat × ΔT
Given:
- Mass of ethanol vapor (m) = 25.0 g
- Specific heat of ethanol liquid (specific heat) = 1.9 J/g°C
- Initial temperature (T1) = 93°C
- Final temperature (T2) = 78.4°C
Calculating the energy released during cooling to boiling point:
Energy1 = 25.0 g × 1.9 J/g°C × (93-78.4)°C
2. Calculate the energy released during the phase change from liquid to solid:
The energy released during the phase change is given by the formula:
Energy = moles × heat of fusion
To calculate the moles of ethanol, we need to convert the mass of ethanol to moles. The molar mass of ethanol (C2H5OH) is 46.07 g/mol.
Moles of ethanol (n) = mass of ethanol (m) / molar mass of ethanol
Given:
- Mass of ethanol (m) = 25.0 g
- Molar mass of ethanol = 46.07 g/mol
- Heat of fusion (ΔHfusion) = 4.60 kJ/mol
Calculating the energy released during the phase change:
Moles of ethanol = 25.0 g / 46.07 g/mol
Energy2 = moles × ΔHfusion
3. Calculate the energy released during the cooling of ethanol liquid from its boiling point (78.4°C) to -10°C:
Given:
- Mass of ethanol liquid (m) = 25.0 g
- Specific heat of ethanol liquid (specific heat) = 2.10 J/g°C
- Initial temperature (T1) = 78.4°C
- Final temperature (T2) = -10°C
Calculating the energy released during cooling:
Energy3 = 25.0 g × 2.10 J/g°C × (78.4-(-10))°C
4. Add up all the energies calculated in steps 1, 2, and 3 to get the total energy released:
Total Energy Released = Energy1 + Energy2 + Energy3
Make sure to convert the units accordingly to obtain the result in kJ.
Following these steps, you can calculate the total energy (in kJ) released when 25.0g of ethanol vapor at 93°C is cooled to -10°C.