Hydrochloric acid reacts with barium hydroxide according to the equation:
2HCl(aq) + Ba(OH)2→ BaCl2(aq) + 2H2O(I) AH-118kJ Calculate the heat (in kJ) associated with the complete reaction of 18.2 grams of HCI (aq).
Molar mass: HCI-36.46 g/mol
(A)-29.5
(B)+29.5
(C)-58.9
(D) +58.9
The Correct Answer and Explanation is :
To calculate the heat (in kJ) associated with the complete reaction of 18.2 grams of HCl (aq), we need to follow a few steps:
Step 1: Determine the moles of HCl
Given that the molar mass of HCl is 36.46 g/mol, we can find the number of moles in 18.2 grams of HCl using the formula:
[
\text{moles of HCl} = \frac{\text{mass of HCl}}{\text{molar mass of HCl}}
]
[
\text{moles of HCl} = \frac{18.2 \, \text{g}}{36.46 \, \text{g/mol}} \approx 0.499 \, \text{mol}
]
Step 2: Use stoichiometry to find the heat change
The balanced chemical equation for the reaction is:
[
2HCl(aq) + Ba(OH)_2 \rightarrow BaCl_2(aq) + 2H_2O(l)
]
The enthalpy change (ΔH) for the reaction is given as -118 kJ, and this corresponds to the heat change for the complete reaction of 2 moles of HCl.
Since we have 0.499 moles of HCl, we can calculate the heat associated with this amount using the following relationship:
[
\text{Heat} = \left(\frac{\text{ΔH}}{\text{moles of HCl in the balanced equation}}\right) \times \text{moles of HCl used}
]
[
\text{Heat} = \left(\frac{-118 \, \text{kJ}}{2 \, \text{mol}}\right) \times 0.499 \, \text{mol}
]
[
\text{Heat} = -29.5 \, \text{kJ}
]
Step 3: Interpret the result
The heat change for the complete reaction of 18.2 grams of HCl is -29.5 kJ. The negative sign indicates that the reaction is exothermic, meaning it releases heat.
Final Answer:
The correct answer is (A) -29.5 kJ.
I’ll now generate a visual representation of the calculation.
Here is the visual representation of the steps for calculating the heat associated with the reaction of HCl and Ba(OH)₂. It outlines the process of determining moles of HCl, the balanced equation, and how the enthalpy change relates to the heat of the reaction. Let me know if you’d like further clarification!
