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# An explanation of the concepts of enthalpy, entropy, spontaneous reactions, and other thermodynamics concepts

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BCl3(g) + NH3(g) <---> Cl3BNH3(s) (<---> represents equilibrium in this case)

The reaction represented above is a reversible reaction.

(a) Predict the sign of the entropy change, ΔS, as the reaction proceeds to the right. Explain your prediction.
(b) If the reaction spontaneously proceeds to the right, predict the sign of the enthalpy change, ΔH. Explain your
prediction.
(c) The direction in which the reaction spontaneously proceeds changes as the temperature is increased above a
specific temperature. Explain.
(d) What is the value of the equilibrium constant at the temperature referred to in (c); that is, the specific
temperature at which the direction of the spontaneous reaction changes? Explain.

https://brainmass.com/chemistry/phase-state-and-energy-changes/enthalpy-entropy-spontaneous-reactions-other-thermodynamics-583422

#### Solution Preview

(a) Predict the sign of the entropy change, ΔS, as the reaction proceeds to the right. Explain your prediction.

Answer: Delta S will be negative

Explanation: Because two molecules on the left side are combining to form one molecule of product, we end up with a loss of gas particles. This lowers the amount of material in the atmosphere, thus decreasing the amount of collisions that can occur. As a result, entropy will be lost, resulting in a negative delta S.

(b) If the reaction spontaneously proceeds to the right, predict the sign of the enthalpy change, ΔH. Explain your
prediction.

Answer: The delta H will be negative

Explanation: Considering the equation ΔG=ΔH-TΔS, ...

#### Solution Summary

Solution clearly discusses enthalpy, entropy, spontaneous reactions, and other thermodynamics. This discussion uses these concepts by solving a multi-part chemical thermodynamics problem. The thermodynamics problem utilizes a reversible reaction BCl3(g) + NH3(g) <---> Cl3BNH3(s).

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