How much energy in kilojoules is released when 25.0 g of ethanol ...

Question

How much energy in kilojoules is released when 25.0 g of ethanol vapor at 93.0 °C is cooled to -11.0 °C? Ethanol has mp = -114.1 °C, bp = 78.3 °C, ΔHvap = 38.56 kJ>mol, and ΔHfusio#n = 4.93 kJ>mol. The molar heat#capacity is 112.3 J>1K mol2 for the liquid and 65.6 J>1K vapor.

Accepted Answer

Hello everyone today. We have the following problem, calculate the amount of heat and killed jules released with 35 g of benzene vapor is cooled from 96 degrees Celsius to 26.4 degrees Celsius. And then we have the following information for benzene, things like the boiling point, the melting point and the entropy of vaporization etcetera etcetera. So since the entropy and heat capacities that were given to us use molds, we need to calculate the moles of benzene to the moles of benzene. And so that's going to be found using the mask that we have our 35 g of benzene and multiplying by the molar mass of benzene, which is one mole of benzene is equal to 78.11 g. And one of units canceled out. We are left with 0.4481 moles of benzene. So we're gonna keep that number for later, It was noted that this reaction cooled from 96°C at 24°C and Benzene underwent a condensation Of 80.09°C, which is the boiling point. And so we essentially need to find the total heat. So it's going to represent it by Q total in Q total is going to be to the heat that was released in the gaseous phase plus the heat from the condensation phase. The condensation plus the heat from the liquid phase. And so since we have all of this other information, we need to actually find the heat from the gas. Right? So we said that the heat, the total heat is the heat released from the cooling and then we have the phase change of the condensation and then that heat that was released from the cooling. So what we're gonna do is we're gonna rearrange this to see that the heat, The gaseous phase is going to be equal to the M.olds that we saw for the 0.4481 moles. We're gonna multiply that By our vaporization specific heat capacity, which was 82.4 jewels, Permal Kelvin. And then we're going to multiply that by the temperature change that we had, that was from 80.09°C -196°C. And this is going to give us negative 587 Jewels or .450 45 jewels. But what we need to do is we also need to multiply this by the conversion factor, that one kg is equal to 10 to the third jewels in order to Get our units in killing jewels. So it's gonna make it to negative 0.587 kg jewels. We'll save that number. And from this, we can actually solve for our heat for the condensation phase. So for confrontation, we're gonna take the same number of moles or 0.4481 moles. We are going to multiply that by the heat of vaporization but it's going to be negative, which is negative 30.72 kg joules per mole. And so why is it negative? It's negative because condensation, the process of condensation is the opposite of vaporization. And so when we solve for this, we're going to get negative 13. kg joules. And so not all we need to do is we need to add these to find the total heat. That's going to be negative 0.5 87 kg joules plus negative 13.766 kg joules plus negative 3.272 kg jewels to give us a total heat of negative 17.6 kg jewels as our final answer. And with that we have answered the question overall. I hope that this helped. And until next time.

Watch next