Homework Help: chemistry

Posted by marcus on Wednesday, November 14, 2012 at 9:24pm.

consider the following changes at constant temperature & pressure

H2O(s) --yields-- H20(l); Delta H1
H2O(l) --yields-- H2O(g); Delta H2
H2O(g) --yields-- H2O(s); Delta H3

Using Hess's law, the sum of the deltas is
a. equal to 0
b. sometimes greater than zero, sometimes less than zero
c. less than 0
d. cannot be determined without the numerical values of delta H
e. greater than 0

I picked e because delta 1 looks to be an endothermic reaction, delta 2 also endothermic, and delta 3 is exothermic reaction. But the answer is equal to 0. Why?

chemistry - DrBob222, Wednesday, November 14, 2012 at 10:01pm
dHsub = dHfusion + dHvaporization
So you add dHfusion to dHvap and you end up with dHsub which means that if you complete the cycle you end you with zero.

Answer this Question

Related Questions

Chemistry - Consider the following data: * NH3(g) yields 1/2 N2(g) + 3/2 H2(g) ...
Chemistry - Calculate the enthalpy of the reaction 2B2H6 + 6O2=2B2O3 +6H2O given...
Chemistry - Mg + 2HCl -> MgCl2 +H2 delta H = ? MgO + 2HCl (aq) -> ...
Chem - RXN #1: H2 (g) + O2 (g) --> H2O2 (l) ; delta-H =? Calculate the ...
Chemistry - Calculate the work involved if a reaction with an enthalpy change of...
Chemistry - H2O (liquid) yields H2O gas delta H= +44kJ. How much heat is evolved...
Chemistry! - Calculate the work involved if a reaction with an enthalpy change ...
chemistry - At constant pressure and 25 degrees C, what is delta H for the ...
Chemistry - Enthalpy changes: H2O2(l) ----> H2O(l) + 1/2P2(g) delta H= -...
chemistry - If heat of reaction, Ca(s) + 2H+(aq) Ca2+(aq) + H2(g) , is - 544 kJ/...

For Further Reading

First Name:
School Subject:
Answer: