Is the sign of delta_rms S degree determined for potassium nitrate (KNO_3) what

Question

Is the sign of delta_rms S degree determined for potassium nitrate (KNO_3) what you expected for a dissolution process? Justify your answer. Based on the determined value for delta H degree for KNO_3, is the dissolution of KNO_3, endothermic or exothermic. Assuming that the determined values for delta_dis H degree and delta_dis S degree are temperature independent, is the dissolution of KNO_3 spontaneous at all temperatures? Justify your answer. Ammonium nitrate (NH_4NO_3) is a highly soluble salt for which the dissolution is endothermic. What can be deduced about delta_is S degree for this compound? Magnesium sulfate (MgSO_4) is a highly soluble salt for which the solubility decreases with increasing temperature. What can be deduced about delta_ G degree, delta_is G degree, delta_dis S degree for this compound?

Explanation / Answer

1The S for KNO3 dissolving in water is always positive since the randomness of the system increases.

2.The H would be positive if heat needs to be provided for KNO3 to dissolve(endothermic).

3.H and S both are temperature dependent.

G = H – TS

If H and S are positive then spontaneous at high temperature while H negative and S positive then spontaneous at all temperature.

4.The dissolution of ammonium nitrate is endothermic and S will be positive value.This dissolution is entropicaly driven, which means that in water, the ions are much more stable solvated than remaining as a solid, to the extent that ambient heat will be absorbed to complete the process.

5.MgSO4--------Mg+2 +SO4-2

Then,G is less than zero,so it is spontaneous.With increase in temperature solubility decrease then

H must be endothermic and S will be positive.

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