# How can we find DeltaH_"rxn"^@ for...? NaOH(s) + HCl(g) rarr NaCl(s) + H_2O(l)?

Apr 9, 2017

#### Answer:

You normally would quote INDIVIDUAL $\Delta {H}_{f}^{\circ}$ for reactants and products.

I get $\Delta {H}_{\text{rxn}}^{\circ} = - 134.7 \cdot k J \cdot m o {l}^{-} 1.$

#### Explanation:

But, we can find $\Delta {H}_{f}^{\circ}$ for the participating species on the interwebz..... :

$N a O H \left(s\right) + H C l \left(g\right) \rightarrow N a C l \left(s\right) + {H}_{2} O \left(g\right)$

And the various $\Delta {H}_{f}^{\circ}$ are taken from the given site.

$N a O H \left(s\right) ,$ $\Delta {H}_{f}^{\circ} = - 426.0 \cdot k J \cdot m o {l}^{-} 1$

$N a C l \left(s\right) ,$ $\Delta {H}_{f}^{\circ} = - 411.2 \cdot k J \cdot m o {l}^{-} 1$

$H C l \left(g\right) ,$ $\Delta {H}_{f}^{\circ} = - 92.3 \cdot k J \cdot m o {l}^{-} 1$

${H}_{2} O \left(g\right) ,$ $\Delta {H}_{f}^{\circ} = - 241.8 \cdot k J \cdot m o {l}^{-} 1$

Now $\Delta {H}_{\text{rxn"^@=SigmaDeltaH_f^@"products"-SigmaDeltaH_f^@"reactants}}$

$\left\{\left(- 241.8 - 411.2\right) - \left(- 426.0 - 92.3\right)\right\} \cdot k J \cdot m o {l}^{-} 1 = - 134.7 \cdot k J \cdot m o {l}^{-} 1$

If I were you, I would check on the $\Delta {H}_{f}^{\circ}$ values. All care taken, but no responsibility admitted.......