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Ch.6 - Thermochemistry
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All textbooksTro 4th EditionCh.6 - ThermochemistryProblem 101a

Chapter 6, Problem 101a

Use standard enthalpies of formation to calculate the standard change in enthalpy for the melting of ice. (The ΔH °f for H2O(s) is -291.8 kJ/mol.)

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hi everyone for this problem, we need to calculate the standard entropy change for conversion of liquid water to steam. So let's go ahead and get started. The first thing that we're going to want to do is write out our equation and so we have the conversion of liquid water to steam. And our equation for calculating the standard entropy change is that our standard entropy change of our reaction is equal to the sum of our products, minus the sum of our reactant. And we're going to need to look up the standard heats of formation for both liquid water and steam or water as gas. And those standard heats of formation are our standard heat of formation of liquid water Is going to equal negative 285.8 killer jewels Permal. And our standard heat of formation of steam or water as a gas is equal to -241. killer joules per mole. Okay, so now we have everything that we need to solve this problem. So let's plug in. So our standard entropy change of our reaction is going to equal. We have to pay attention to how many moles we have of everything. So our products, we have one product and we only have one mole of it. So we're going to multiply that one mole by its standard heat a formation. So for H 20 gas we said it's negative 241.8 kg joules per mole and we're going to minus our reactant. So we have one mole of H 20 liquid and its standard heat of formation is negative 285.8 killer jewels per more. Okay, so because we only have one mole of each, that makes this a little simple. So we're just going to have negative 241. kg joules per mole minus negative 285.8 kg jewels per mole. And this is going to give us our standard entropy change for our reaction. and so we're going to get a final answer of positive 40 for killer jewels per mole. And that is the answer to this problem. This is the standard entropy change for a conversion of liquid water to steam. That's the end of this problem. I hope this was helpful.
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