a) -1153 kJ b) -1124 kJ c) -1395 kJ d) -1199 kJ a) -765 J/mol K b) -410.9 J/mol
ID: 838185 • Letter: A
Question
a) -1153 kJ
b) -1124 kJ
c) -1395 kJ
d) -1199 kJ
a) -765 J/mol K
b) -410.9 J/mol K
c) 763.8 J/mol K
d) -252.5 J/mol K
a) 4023 J/mol K
b) -761 J/mol K
c) 3258 J/mol K
d) -4788 J/mol K
4. At what temperature will the process stop being spontaneous?
a) 298 K
b) 1567 K
c) 368 K
d) 759 K
a) -229 kJ
b) -586 kJ
c) -971 kJ
d) -1427 kJ
a) -969 kJ
b) -39 kJ
c) 182 kJ
d) -572 kJ
Glycine, H2NCH2COOH, is an amino acid found in proteins. Some bacteria make glycine by reacting ammonia, methane and oxygen according to the following reaction (at 298 K):Explanation / Answer
1. To find the ?Hrxn we apply the general equation below:
?Hrxn = (??Hproducts) - (??Hproducts)
Keep in mind that the ?H values given are in kJ/mol, so we have to multiply each ?H value by its stoichiometric coefficient from the reaction equation. Thus we get:
?Hrxn = (?HH2O + ?HH2NCH2COOH) - (?HCH4 + ?HNH3 + ?HO2)
?Hrxn =(3 mol(-285.8 kJ/mol) + 1 mol(-537.2 kJ/mol)) - (2 mol(-74.9 kJ/mol) + 1 mol(-46.2 kJ/mol) + 5/2 mol(0 kJ/mol))
?Hrxn = (-1394.6 kJ) - (-196 kJ) = -1198.6 kJ
So the answer is (d)
----
2) We apply the same formula to find ?Srxn
?Srxn = (??Sproducts) - (??Sproducts)
?Srxn = (3 mol(70.0 J/mol K) + 1 mol(103.5 J/mol K)) - (2 mol(186.6 J/mol K) + 1 mol(192.8 J/mol K) + 5/2 mol(205 J/mol K))
?Srxn = (313.5 J/ K) - (1078.5 J/ K) = -765 J/K
Thus the answer is (a)
----
3) We can calculate the ?Suniverse as follows:
?Suniverse = ?Ssurroundings + ?Srxn
And we can find ?Ssurroundings = ?Hrxn / T = -1199 kJ / 298 K = -4.02 kJ / K = -4.02 x 103 J /K
Thus: ?Suniverse = -4.02 x 103 J /K - 765 J/K = -4.79 x 103 J/K = -4790 J/K
Thus the answer is (d).
---
4) I find the easiest way to answer is is to first calculate ?Grxn from the equation:
?Grxn = ?Hrxn - T?Srxn
If ?Grxn > 0, then the reaction is non-spontaneous. So we want to enforce this condition and solve for T:
0 > ?Hrxn - T?Srxn
T?Srxn > ?Hrxn
T > ?Hrxn / ?Srxn
T > -1199 kJ / -0.765 J/K = +1567 K
Thus the answer is (b).
-----
5) We can calculate ?Grxn from the equation below:
?Grxn = ?Hrxn - T?Srxn = (-1199 kJ) - (298 K)(-0.765 kJ/K) = -1199 kJ + 228 kJ = -971 kJ
Thus the answer is (c).
----
6) Are you sure we're not missing information for this?
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.