*We are asked to determine the ***ΔH°**_{rxn} for the reaction*: *

*Ca(OH)*_{2}* + *2* H*_{3}*AsO*_{4}* → Ca(H*_{2}*AsO*_{4}*)*_{2}* + *2* H*_{2}*O *

We can use the following equation to solve for **ΔH˚ _{rxn}**:

$\overline{){\mathbf{\Delta H}}{{\mathbf{\xb0}}}_{{\mathbf{rxn}}}{\mathbf{=}}{\mathbf{\Delta H}}{{\mathbf{\xb0}}}_{\mathbf{f}\mathbf{,}\mathbf{}\mathbf{prod}}{\mathbf{-}}{\mathbf{\Delta H}}{{\mathbf{\xb0}}}_{\mathbf{f}\mathbf{,}\mathbf{}\mathbf{react}}}$

Note that we need to *multiply each ΔH˚ _{f} by the stoichiometric coefficient* since ΔH˚

Also, note that ΔH˚_{f} for elements in their standard state is 0.

Given the data in the table on the right, the **ΔH°**_{rxn} for the reaction:

** Ca(OH)_{2} + 2 H_{3}AsO_{4} → Ca(H_{2}AsO_{4})_{2} + 2 H_{2}O ** is ___________ kJ.

A. -744.9

B. -4519

C. -4219

D. -130.4

E. -76.4

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Enthalpy of Formation concept. You can view video lessons to learn Enthalpy of Formation. Or if you need more Enthalpy of Formation practice, you can also practice Enthalpy of Formation practice problems.