Chemistry Forum

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.
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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) \(ΔH°_r=0\), \(ΔS°_r<0\).
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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)\(ΔH°_r<0\), \(ΔS°_r>0\), \( ΔG°_r>0 \).
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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.
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My answers are:
1) a
2) a
3) c
4) b

Are my answers correct?

Correct.

Wow thanks