Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J...
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Transcript of Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J...
![Page 1: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/1.jpg)
Energy, entropy and equilibrium
![Page 2: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/2.jpg)
These are some standard entropy values. Notice that the units are J K–1 mol–1. These are different from the units for enthalpy, kJ mol–1.
![Page 3: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/3.jpg)
Let's work out the standard entropy change, ΔSө, for the decomposition of calcium carbonate.
![Page 4: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/4.jpg)
We need to know the total standard entropy of the products and the total standard entropy of the reactants.
![Page 5: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/5.jpg)
First, add up all the entropy values for the products, in this case calcium oxide and carbon dioxide.
![Page 6: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/6.jpg)
Next, subtract all the entropy values for the reactants. In this case there is only one, calcium carbonate.
![Page 7: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/7.jpg)
The standard entropy change for the decomposition of calcium carbonate is positive.
![Page 8: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/8.jpg)
These are some standard entropy values. Notice that the units are J K–1 mol–1. These are different from the units for enthalpy, kJ mol–1.
![Page 9: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/9.jpg)
Let's work out the standard entropy change, ΔSө, for the synthesis of ammonia.
![Page 10: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/10.jpg)
We need to know the total standard entropy of the products and the total standard entropy of the reactants.
![Page 11: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/11.jpg)
First, add up all the entropy values for the products, in this case ammonia. Note that we multiply its entropy value by 2.
![Page 12: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/12.jpg)
Next, subtract all the entropy values for the reactants, starting with nitrogen.
![Page 13: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/13.jpg)
Note that we multiply the entropy value for hydrogen by 3.
![Page 14: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/14.jpg)
Remember to multiply where necessary.
![Page 15: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/15.jpg)
The standard entropy change for the synthesis of ammonia is positive.
![Page 16: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/16.jpg)
We can work out the entropy change in the surroundings when a chemical change occurs.
![Page 17: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/17.jpg)
To do this we need to know the enthalpy change and the temperature at which the reaction occurs.
![Page 18: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/18.jpg)
If we know the entropy change for the reaction (the system) and the entropy change for the surroundings, we can work out the total entropy change.
![Page 19: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/19.jpg)
First calculate the enthalpy change, ΔH, for the reaction.
![Page 20: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/20.jpg)
The enthalpy change is 92.4 kJ mol–1. Remember to multiply by 1000 because entropy values are in J K–1 mol–1.
![Page 21: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/21.jpg)
Divide by the temperature, in this example 298 K.
![Page 22: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/22.jpg)
The entropy change in the surroundings in this example is –310 J K–1 mol–1.
![Page 23: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/23.jpg)
Now let's calculate the total entropy change.
![Page 24: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/24.jpg)
First, substitute the entropy change for the surroundings that we have just calculated.
![Page 25: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/25.jpg)
Next, substitute the entropy change for the system. In this example it is +93 J K–1 mol–1.
![Page 26: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/26.jpg)
The total entropy change here is negative. As it would lead to a decrease in entropy, the reaction would not happen spontaneously at 298 K.
![Page 27: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/27.jpg)
The total entropy change must be positive for a reaction to happen. If it is zero, the reaction forms an equilibrium.
![Page 28: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/28.jpg)
The total entropy change must be positive for a reaction to happen. If it is zero, the reaction forms an equilibrium.
![Page 29: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/29.jpg)
We can work out the minimum temperature at which the total entropy change is zero.
![Page 30: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/30.jpg)
We can work out the minimum temperature at which the total entropy change is zero.
![Page 31: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/31.jpg)
This equation shows the relationship between the enthalpy change, the temperature and the entropy change of the system when the total entropy change is zero.
![Page 32: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/32.jpg)
We can rearrange the equation to find the temperature at which the total entropy change is zero.
![Page 33: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/33.jpg)
The enthalpy change when ice melts is 6.01 kJ mol–1, which is 6010 J mol–1. The corresponding change in the entropy of the system is 22 J K–1 mol–1.
![Page 34: Energy, entropy and equilibrium. These are some standard entropy values. Notice that the units are J K –1 mol –1. These are different from the units for.](https://reader030.fdocuments.in/reader030/viewer/2022032707/56649e155503460f94aff27f/html5/thumbnails/34.jpg)
The total entropy will be zero at 273 K or 0 °C. At this temperature, ice and liquid water exist together in equilibrium.