Consider the following reaction at 298 K:
C(graphite) +2Cl2 (g) -----> CCl4(l)
Calculate the following quantities.
Delta H: -139 kJ/mol
deltaS(sys)=? J/mol*K
deltaS(surr)=? J/mol*K
deltaS(univ)=? J/mol*K
My answer is:
deltaS(sys)=-253.3J/mol*K
deltaS(surr)=466.4 J/mol*K
deltaS(univ)=231.4 J/mol*K
Delta (surr) and (univ) are correct. But delta (sys) is wrong...please help thanks!
chemistry - DrBob222, Friday, March 16, 2012 at 11:38pm
How did you calculate the dS sys? What values did you use?
chemistry - Leila, Saturday, March 17, 2012 at 2:40pm
Change in Hf(kJ/mol) Change in G Change in S
C(graphite) 0 0 5.7
Cl2 0 0 223.1
CCl4 -139 -68.6 214.4
Leila
answered
C(graphite):
change in delta Hf=0
change in delta G= 0
change in delta S= 5.7
Cl2
change in delta Hf=0
change in delta G= 0
change in delta S= 223.1
CCl4
change in delta Hf=-139
change in delta G= -68.6
change in delta S= 214.4
Leila
answered
Leila
answered
Explain Bot
answered
deltaS = n * deltaS°(products) - m * deltaS°(reactants)
Where:
- deltaS is the change in entropy
- n and m are the stoichiometric coefficients of the products and reactants
- deltaS° is the standard entropy change for each species
Using the values you provided, the calculation for deltaS(sys) can be done as follows:
deltaS(sys) = (1 * 214.4) - (1 * 0 + 2 * 223.1)
= 214.4 – 446.2
= -231.8 J/mol*K
Therefore, the correct value for deltaS(sys) is -231.8 J/mol*K, not -253.3 J/mol*K as stated in your answer.
To calculate deltaS(surr), we can use the equation:
deltaS(surr) = -deltaH(sys) / T
Where:
- deltaH(sys) is the enthalpy change of the system (given as -139 kJ/mol)
- T is the temperature in Kelvin (298 K)
deltaS(surr) = -(-139 kJ/mol) / (298 K)
= 466.4 J/mol*K
Therefore, the value for deltaS(surr) is indeed 466.4 J/mol*K.
Lastly, to calculate deltaS(univ), it can be done using the equation:
deltaS(univ) = deltaS(sys) + deltaS(surr)
deltaS(univ) = -231.8 J/mol*K + 466.4 J/mol*K
= 234.6 J/mol*K
Therefore, the correct value for deltaS(univ) is 234.6 J/mol*K, not 231.4 J/mol*K as stated in your answer.
I hope this helps clarify the calculation and provides you with the correct values for deltaS(sys), deltaS(surr), and deltaS(univ).
