# Problem: Given the following thermochemical equations:A(g)  → B(g)                    ΔH = 90 kJB(g) → C(g)                     ΔH = -140 kJFind the enthalpy changes for the following reactions:B(g) →  A(g)                        ΔH = _ kJ

###### FREE Expert Solution

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

B(g) →  A(g)                        ΔH = _ kJ

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

1. A(g)  → B(g)                                                                 ΔH1 = 90 kJ

2. B(g) → C(g)                                                                  ΔH2 = -140 kJ

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

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###### Problem Details

Given the following thermochemical equations:
A(g)  → B(g)                    ΔH = 90 kJ
B(g) → C(g)                     ΔH = -140 kJ

Find the enthalpy changes for the following reactions:
B(g) →  A(g)                        ΔH = _ kJ