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!
How did you calculate the dS sys? What values did you use?
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
delta Ssys is -237.49
Sure, let me help you with that! So, to calculate the change in entropy for the system (deltaS(sys)), we can use the equation:
deltaS(sys) = (deltaH) / (T)
where deltaH is the enthalpy change of the reaction and T is the temperature in Kelvin.
In this case, deltaH is given as -139 kJ/mol, but we need to convert it to J/mol, so it becomes -139,000 J/mol. The temperature is given as 298 K.
Substituting these values into the equation, we get:
deltaS(sys) = (-139,000 J/mol) / (298 K)
Calculating this, we get:
deltaS(sys) ≈ -466.4 J/mol*K
So the correct value for deltaS(sys) is -466.4 J/mol*K, which is different from your initial answer. Keep in mind that entropy change values can have different signs depending on the process, so negative values are not uncommon.
As for deltaS(surr) and deltaS(univ), it seems you already have the correct values, so well done on that!
I hope this clears up any confusion. Let me know if you have any other questions!
To calculate the change in entropy of the system (ΔSsys), we can use the equation:
ΔSsys = ΔH / T
Where:
ΔH = enthalpy change of the reaction (given as -139 kJ/mol)
T = temperature in Kelvin (298 K in this case)
Plugging in the values:
ΔSsys = (-139 kJ/mol) / (298 K)
It's important to convert the units properly to maintain consistency. In this case, convert kJ to J by multiplying by 1000, and the answer will be in J/mol*K.
ΔSsys = (-139 kJ/mol) / (298 K) * 1000 = -466.4 J/mol*K
Therefore, ΔSsys should be -466.4 J/mol*K, not -253.3 J/mol*K as you mentioned.
The correct answers would be:
ΔS(sys) = -466.4 J/mol*K
ΔS(surr) = 466.4 J/mol*K
ΔS(univ) = 231.4 J/mol*K