Homework Help: Chemistry

Posted by Katrina on Wednesday, May 9, 2007 at 8:22pm.

Hello Jiskha,

I'm hoping you are able to help me with my homework. Its on General Chemistry.

Question One
- When the solid NH4NO3 is dissolved in water at 25 C, the temperature of the solution decreases. What is true about the signs of enthalpy (H) and (S) for this process?

Question Two
- When a liquid evaporates, which is true about the signs of the enthalpy and entropy changes?

Question Three
- A temperature change causes the volume of a solution to increase. This change will cause:

a) the molarity and molality to increase
b) the molarity and molality to decrease
c) the molarity to inscrease but not change the molality
d) the molarity to decrease but not change the molality
e) neither the molarity nor molality to change

Thanks in advance for any help that is given. Will be much appreciated.

~ Katrina

I don't want to go through and duplicate what you may already know. Please indicate what you think about the answers and why and someone will critique your work. If you don't know where to start, please tell us what you don't understand about it.

I'm confused about these questions but I guess these answers could be possible. Let me know if i'm wrong and why. Will really appreciated it.

1) H is positive and S is negative ?
2) Both H & S are positive ?
3) Neither changes ?

Chemistry - Sap, Friday, February 3, 2012 at 12:06am
Water definitely lose (-ve or exothermic) energy. But NH4NO3 gain this heat (+ve). So NH4NO3 solution gained heat from water and water got it from the surrounding so overall gained heat +ve

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