Final answer:
To find the heat released when 23.0 g of HCl is formed, you calculate the moles of HCl and use the given ΔH° to find that approximately -70.7 kJ of heat is released, making the correct answer c. -70.7 kJ.
Step-by-step explanation:
The student's question is about calculating the amount of heat released when a specific mass of HCl is formed in a chemical reaction, where the reaction's enthalpy change (ΔH°) is given as -336 kJ. To solve this problem, you need to first calculate the number of moles of HCl that correspond to the given mass (23.0 g). The molar mass of HCl is approximately 1 (for H) + 35.5 (for Cl) = 36.5 g/mol. Therefore, the number of moles of HCl formed is 23.0 g ÷ 36.5 g/mol which equals roughly 0.6301 mol.
Since the ΔH° value refers to the enthalpy change for the reaction as written, which produces 3 moles of HCl, we can calculate the energy released for the formation of 0.6301 moles of HCl by using the ratio method:
ΔH (for 0.6301 mol) = (0.6301 mol ÷ 3 mol) × (-336 kJ)
By solving the above, we get that the heat released is approximately -70.7 kJ. Therefore, the correct answer is c. -70.7 kJ.