Questions of thermodynamics

Chemistry and homework help forum.

Organic Chemistry, Analytical Chemistry, Biochemistry, Physical Chemistry, Computational Chemistry, Theoretical Chemistry, High School Chemistry, Colledge Chemistry and University Chemistry Forum.

Share your chemistry ideas, discuss chemical problems, ask for help with scientific chemistry questions, inspire others by your chemistry vision!

Please feel free to start a scientific chemistry discussion here!

Discuss chemistry homework problems with experts!

Ask for help with chemical questions and help others with your chemistry knowledge!

Moderators: expert, ChenBeier, Xen

Post Reply
User avatar
anto007
Sr. Member
Sr. Member
Posts: 27
Joined: Tue Aug 10, 2021 10:13 am
Location: Italy

Questions of thermodynamics

Post by anto007 »

1) If \( ΔG°_r<0 \) for a reaction at all temperature, then \(ΔH°_r\) is___ and \(ΔS°_r\) is____
a) negative, positive.
b) positive, negative.
c) negative, negative.
d) positive, positive.
e) positive, either positive or negative.
_____________________________________________________________________________________________________________________________
2)Hydrogen gas is non-pollution fuel. Hydrogen gas may be preparates by electrolysis of water:
2H2O (l) --->2H2 (g) + O2 (g)
Predict the signs of \(ΔH°_r\) and \(ΔS°_r\) for the production of hydrogen gas by electrolysis of water.
a) \(ΔH°_r>0\), \(ΔS°_r>0\).
b) \(ΔH°_r<0\), \(ΔS°_r>0\).
c) \(ΔH°_r>0\), \(ΔS°_r<0\).
d) \(ΔH°_r<0\), \(ΔS°_r<0\).
e) \(ΔH°_r=0\), \(ΔS°_r<0\).
______________________________________________________________________________________________________________________________
3)The dissolution of ammonium nitrate occours spontaneously in water at 25°C. As NH4NO3 📖 dissolves, the temperature decreases. Whta are the signs of \(ΔH°_r\), \(ΔS°_r\) and \( ΔG°_r \) for this process?

a)\(ΔH°_r>0\), \(ΔS°_r<0\), \( ΔG°_r>0 \).
b)\(ΔH°_r>0\), \(ΔS°_r>0\), \( ΔG°_r>0 \).
c)\(ΔH°_r>0\), \(ΔS°_r>0\), \( ΔG°_r<0 \).
d)\(ΔH°_r<0\), \(ΔS°_r<0\), \( ΔG°_r<0 \).
e)\(ΔH°_r<0\), \(ΔS°_r>0\), \( ΔG°_r>0 \).
______________________________________________________________________________________________________________________________
4)At what temperature will a reactio be spontaneous if \(ΔH°_r=+45 kJ\) and \(ΔS°_r=+312 J/K\)?

a)All temperatures below \(144 K\).
b) All temperatures above \(144 K\).
c) Temperatures between \(45 K\) and \(312 K\).
d)The raction will be spontaneous at any temperature.
e)The reaction will never be spontaneous.
______________________________________________________________________________________________________________________________
My answers are:
1) a
2) a
3) c
4) b

Are my answers correct?
The mind is like a parachute, it only works if it opens. -A. Einstein
User avatar
ChenBeier
Distinguished Member
Distinguished Member
Posts: 906
Joined: Wed Sep 27, 2017 7:25 am
Location: Berlin, Germany

Re: Questions of thermodynamics

Post by ChenBeier »

Correct.
User avatar
anto007
Sr. Member
Sr. Member
Posts: 27
Joined: Tue Aug 10, 2021 10:13 am
Location: Italy

Re: Questions of thermodynamics

Post by anto007 »

Wow 8) thanks
The mind is like a parachute, it only works if it opens. -A. Einstein
Post Reply