🤓 Based on our data, we think this question is relevant for Professor Gray's class at CSU.

Solution: Given the following reactionsH2O (l) →H2O (g)                    ΔH = 44.01 kJ2H2 (g) + O2 (g) → 2H2O (g)  ΔH = -483.64 kJthe enthalpy for the decomposition of liquid water into gaseous hydrogeand oxygen2H2O (l) → 2H2 (g) + O2 (g) is __________ kJ.A) -395.62B) -527.65C) 439.63D) 571.66E) 527.65

Problem

Given the following reactions

H2O (l) →H2O (g)                    ΔH = 44.01 kJ

2H2 (g) + O2 (g) → 2H2O (g)  ΔH = -483.64 kJ

the enthalpy for the decomposition of liquid water into gaseous hydrogeand oxygen

2H2O (l) → 2H2 (g) + O2 (g) 

is __________ kJ.

A) -395.62

B) -527.65

C) 439.63

D) 571.66

E) 527.65

Solution

We’re being asked to determine the enthalpy change (ΔHrxn) for the chemical reaction:


2 H2O (l) → 2 H2 (g) + O2 (g) 


We can use Hess’s Law to determine the enthalpy change of the overall reaction from the given reactions:


1. H2O (l) →H2O (g)                                                         ΔH1 = 44.01 kJ

2. 2H2 (g) + O2 (g) → 2H2O (g)                                        ΔH2 = - 483.64 kJ


We now need to find a combination of reactions that when added up, gives us the overall reaction.


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