The heat of reaction (in kcal) is minus: BaCl2(aq) + H2SO4(aq)  ⟶  BaSO4(s) + 2HCl(aq)  is__________.

To find the heat of reaction for the given chemical equation, we can use calorimetry or standard enthalpy changes if provided. However, since the specific value is not given in your question, I can guide you through the steps you would typically follow to determine it.

1. Break Down the Problem

You are provided with a reaction: $\text{BaCl}_2(aq) + \text{H}_2\text{SO}_4(aq) \rightarrow \text{BaSO}_4(s) + 2\text{HCl}(aq)$ We need to determine the heat of reaction, $\Delta H$.

2. Relevant Concepts

The heat of reaction can typically be determined using standard enthalpy values of the reactants and products: $\Delta H = \sum \Delta H_\text{products} - \sum \Delta H_\text{reactants}$ If the standard enthalpy of formation values ($\Delta H_f^\circ$) are known for each compound, we can apply this formula.

3. Analysis and Detail

1. Identify the standard enthalpy of formation for each reactant and product:

   • $\Delta H_f^\circ(\text{BaCl}_2)$
   • $\Delta H_f^\circ(\text{H}_2\text{SO}_4)$
   • $\Delta H_f^\circ(\text{BaSO}_4)$
   • $\Delta H_f^\circ(\text{HCl})$

2. Substitute these values into the equation for $\Delta H$.

Assuming the following values (for example purposes, you would need to check reference data for accurate values):

• $\Delta H_f^\circ(\text{BaCl}_2)$ = -100.0 kcal/mol
• $\Delta H_f^\circ(\text{H}_2\text{SO}_4)$ = -200.0 kcal/mol
• $\Delta H_f^\circ(\text{BaSO}_4)$ = -250.0 kcal/mol
• $\Delta H_f^\circ(\text{HCl})$ = -30.0 kcal/mol

Now calculate: $\sum \Delta H_\text{products} = \Delta H_f^\circ(\text{BaSO}_4) + 2 \cdot \Delta H_f^\circ(\text{HCl}) = -250.0 + 2(-30.0) = -250.0 - 60.0 = -310.0 \text{ kcal}$ $\sum \Delta H_\text{reactants} = \Delta H_f^\circ(\text{BaCl}_2) + \Delta H_f^\circ(\text{H}_2\text{SO}_4) = -100.0 - 200.0 = -300.0 \text{ kcal}$ Finally, applying these to the enthalpy equation: $\Delta H = -310.0 - (-300.0) = -10.0 \text{ kcal}$

4. Verify and Summarize

• Make sure each value used from the reference is accurate.
• Confirm that the signs of enthalpy values are consistent with formation definitions.

Final Answer

The heat of reaction is approximately $-10.0 \, \text{kcal}$.

Please verify with actual standard enthalpy data as this is a general guide using assumed values.