Which of the following reactions have a positive ÄSrxn? Check all that apply.
A(g) + B(g)--> C(g)
2A(g) + B(g)--> 4C(g)
A(s) + B(g)--> 2C(g)
2A(g) + 2B(g)--> 3C(g)
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To determine which of the given reactions have a positive ÄSrxn, we need to analyze the change in entropy (ÄS) between the reactants and products for each reaction.
Entropy is a measure of the disorder or randomness of a system. If the disorder increases in going from reactants to products, the value of ÄS is positive. If the disorder decreases, the value of ÄS is negative.
To analyze the change in entropy for each reaction, we need to consider the states of the reactants and products. Here's how you can do it:
1. Reaction A(g) + B(g) --> C(g):
Since all the species are gases, there is no change in the states from reactants to products. This means there is neither an increase nor decrease in disorder. Thus, the ÄS for this reaction is most likely zero.
2. Reaction 2A(g) + B(g) --> 4C(g):
In this reaction, the number of gas molecules increases from 3 on the left side to 4 on the right side. This indicates an increase in disorder, so the ÄS for this reaction is positive.
3. Reaction A(s) + B(g) --> 2C(g):
The reactant A is a solid, while the products C are gases. The conversion of a solid to gases increases the disorder, resulting in a positive ÄS for this reaction.
4. Reaction 2A(g) + 2B(g) --> 3C(g):
In this reaction, the number of gas molecules increases from 4 on the left side to 3 on the right side. This indicates a decrease in disorder, so the ÄS for this reaction is most likely negative.
Based on the analysis above, the reactions that have a positive ÄSrxn are:
- 2A(g) + B(g) --> 4C(g)
- A(s) + B(g) --> 2C(g)
Please note that a more accurate determination of ÄSrxn requires considering additional factors, such as temperature and ΔH (enthalpy) values.