Predicting the Spontaneity of 2BH3(g)->B2H6(g): Help Needed!

In summary, the conversation discusses the reaction 2BH3(g)->B2H6(g) and the possible outcomes of its spontaneity and enthalpy. The participants mention that DSsystem is negative and that further information on DH is needed to determine the nature of the reaction. They also mention that access to certain resources may not be allowed during exams, making it difficult to make a definite conclusion. However, it is suggested that the reaction is exothermic due to the synthesis reaction taking place and the electron deficiency of Borane. The spontaneity of the reaction cannot be determined without more information.
  • #1
yolo123
63
0
2BH3(g)->B2H6(g)

Which is true?
a) Reaction is always spontaneous.
b) Reaction is always non-spontaneous.
c) Reaction is sometimes spontaneous sometimes not.
d) Reaction is endothermic.
e) Two of the above are true.


I know DSsystem is negative. But I would need more information on DH to say anything else. Please help me!
 
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  • #2
yolo123 said:
2BH3(g)->B2H6(g)

Which is true?
a) Reaction is always spontaneous.
b) Reaction is always non-spontaneous.
c) Reaction is sometimes spontaneous sometimes not.
d) Reaction is endothermic.
e) Two of the above are true.


I know DSsystem is negative. But I would need more information on DH to say anything else. Please help me!

http://www.nist.gov/data/PDFfiles/jpcrd544.pdf
 
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  • #3
Chestermiller, we cannot have access to these ressources in exams. We should do it without references. Can we say for sure that the reaction is exothermic since the reaction is a synthesis reaction?
 
  • #4
yolo123 said:
Chestermiller, we cannot have access to these ressources in exams. We should do it without references. Can we say for sure that the reaction is exothermic since the reaction is a synthesis reaction?
Sorry. I can't help you on this, if that is the case. Please check with Borek who is very knowledgeable.

Chet
 
  • #5
No idea, which is why I have not commented earlier. Perhaps the data were given in other parts of the test?
 
  • #6
If this is asked in test, from my experience, you just have to consider that Borane, being electron deficient molecule, tried to remove the deficit by dimerizing (making bond). Hence you could say that the change in Enthalpy is negative. However, it is difficult to say about the spontaneity all by itself, except it can be below certain temperature.

Remember, if this is just a test, my reasoning is a valid flying guess (at least in the type of tests I gave during my college entrance preparations)
 

1. Can you explain the concept of spontaneity in chemical reactions?

Spontaneity in chemical reactions refers to the tendency of a reaction to occur without any external influence or energy input. In other words, it is the measure of how likely a reaction is to happen on its own without any additional energy. It is determined by the change in Gibbs free energy (ΔG) of the reaction, with negative values indicating spontaneous reactions.

2. How can we predict the spontaneity of a chemical reaction?

The spontaneity of a chemical reaction can be predicted by calculating the change in Gibbs free energy (ΔG) using the formula ΔG = ΔH - TΔS, where ΔH is the change in enthalpy and ΔS is the change in entropy. If ΔG is negative, the reaction is spontaneous; if it is positive, the reaction is non-spontaneous; and if it is zero, the reaction is at equilibrium.

3. What factors affect the spontaneity of a chemical reaction?

The spontaneity of a chemical reaction is affected by several factors, including the nature of the reactants and products, temperature, pressure, and concentration. Reactions that involve highly unstable or reactive substances are more likely to be spontaneous, while reactions involving stable compounds may require external energy to occur. Higher temperatures and lower pressures typically favor spontaneity, as well as higher concentrations of reactants.

4. How does the spontaneity of 2BH3(g)→B2H6(g) compare to other reactions?

The spontaneity of this particular reaction (2BH3(g)→B2H6(g)) can vary depending on the temperature and pressure conditions. At standard conditions, the reaction is not spontaneous, as the change in Gibbs free energy (ΔG) is positive. However, at higher temperatures and lower pressures, the reaction becomes spontaneous due to the increase in entropy (ΔS) of the system.

5. What applications does predicting spontaneity of chemical reactions have?

Predicting the spontaneity of chemical reactions is important in various industries, such as pharmaceuticals, energy production, and materials science. It helps researchers understand and control the rate and direction of chemical reactions, which is crucial in developing new products and processes. Additionally, knowledge of the spontaneity of a reaction can aid in the design and optimization of industrial processes to increase efficiency and reduce costs.

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