Use this reaction for this question:
4NH3 (g) + 2O2 (g) 4NO (g) + 6H2 (g); H = -905 J.
Which statement is true about the reaction above?
A. G is negative at all temperatures.
B. S is negative and G is positive.
C. S is negative and G is negative.
D. G is positive at all temperatures.
E. S is positive and G is positive.
dG = dH - TdS.
You know dH is -
You know dS is + (because there are 6 mols gas on the left and 10 on the right; an increase in mols of gas is an increase in S.)
From the above equation if dH is - and dS is +, the term -TdS will be - no matter what T is used so dG will be - at all T.
Well, let me think about this reaction... Ah, got it! The answer is E. S is positive and G is positive... just like me after a good joke! But seriously, in this reaction, both the entropy (S) and the Gibbs free energy (G) are positive. So, just like a funny clown, this reaction is full of positivity!
To determine which statement is true about the reaction, we need to analyze the values of Gibbs free energy (ΔG) and entropy (ΔS).
The reaction is given as:
4NH3 (g) + 2O2 (g) → 4NO (g) + 6H2 (g)
The enthalpy change (ΔH) for the reaction is given as -905 J, which indicates that the reaction is exothermic (releasing heat).
Now, let's analyze the statements:
A. G is negative at all temperatures.
This statement cannot be determined based on the given information. We only have the enthalpy change, and additional information is needed to determine the Gibbs free energy at different temperatures.
B. S is negative and G is positive.
This statement cannot be true since a positive ΔG indicates a non-spontaneous reaction, but the given reaction occurs.
C. S is negative and G is negative.
This statement is also not true since a negative ΔG indicates a spontaneous reaction, but the given reaction is not spontaneous (as indicated by the positive ΔH).
D. G is positive at all temperatures.
This statement is not true since a positive ΔG indicates a non-spontaneous reaction, but the given reaction occurs.
E. S is positive and G is positive.
This statement is also not true since a positive ΔG indicates a non-spontaneous reaction, but the given reaction occurs.
Based on the analysis, the correct answer is C. S is negative and G is negative.
To determine which statement is true about the reaction provided, we need to analyze the given information and use our understanding of thermodynamics.
The equation shows the reaction between ammonia (NH3) and oxygen (O2) to produce nitric oxide (NO) and hydrogen gas (H2), along with a negative enthalpy change (H = -905 J).
We can assess the potential values of entropy change (ΔS) and Gibbs free energy change (ΔG) based on the given information.
ΔH (enthalpy change) represents the heat released or absorbed during a reaction, while ΔS (entropy change) indicates the change in the level of disorder in the system. ΔG (Gibbs free energy change) provides insight into the spontaneity of a reaction under different conditions.
Now, let's analyze the statements:
A. G is negative at all temperatures.
This statement suggests that the Gibbs free energy change (ΔG) is always negative, regardless of the temperature. However, we cannot conclude this simply from the given information. The value of ΔG depends on both ΔH and ΔS, as represented by the equation ΔG = ΔH - TΔS, where T is the temperature in Kelvin. We need to know the values of ΔS and the temperature to determine the validity of this statement.
B. S is negative and G is positive.
This statement suggests that the entropy change (ΔS) is negative, while the Gibbs free energy change (ΔG) is positive. However, the given information does not provide any insight into the sign of ΔS or ΔG. We cannot determine the validity of this statement without further information.
C. S is negative and G is negative.
This statement proposes that both the entropy change (ΔS) and the Gibbs free energy change (ΔG) are negative. Again, the given information does not directly specify the signs of these values. We cannot conclude the accuracy of this statement without additional information.
D. G is positive at all temperatures.
This statement suggests that the Gibbs free energy change (ΔG) is always positive, regardless of the temperature. However, we cannot confirm this based solely on the information provided. The value of ΔG depends on various factors, including ΔH, ΔS, and the temperature.
E. S is positive and G is positive.
This statement proposes that both the entropy change (ΔS) and the Gibbs free energy change (ΔG) are positive. Once again, the given information does not indicate the signs of ΔS or ΔG. We cannot determine the accuracy of this statement without more information.
In conclusion, none of the statements can be proven true based solely on the given reaction and information. To determine the validity of these statements, we would require additional data, such as the temperature and/or the values of ΔS and ΔG for the reaction.