One reaction of iron with hydrochloric acid is represented by the following thermochemical equation.

Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g); ΔH°= –87.9 kJ
How much heat is liberated at constant pressure if 0.416 g of iron reacts with 42.0 mL of 0.457 M HCl?

Determine the limiting reagent. I believe that is Fe but you must confirm that.

Then 87.9 x (0.416/55.85) = ?? kJ.

The answer doesn't fit with the choices given.

To find out how much heat is liberated during the reaction, we need to use the given information and the equation's stoichiometry. Here's how we can calculate it step by step:

1. Convert the mass of iron from grams to moles:
Given mass of iron = 0.416 g
Molar mass of iron (Fe) = 55.8 g/mol
Moles of iron = (0.416 g) / (55.8 g/mol)

2. Determine the limiting reagent:
We need to compare the moles of iron to the moles of HCl to determine the limiting reagent.
The stoichiometric ratio from the balanced equation tells us that 1 mole of Fe reacts with 2 moles of HCl.
However, we need to convert the volume of HCl to moles first.

a) Convert the volume of HCl from milliliters to liters:
Given volume of HCl = 42.0 mL
Volume of HCl = (42.0 mL) / 1000 mL/L

b) Calculate moles of HCl using the molarity (M) formula:
Molarity (M) = Moles of solute / Volume of solution (L)
Moles of HCl = Molarity (HCl) x Volume (HCl)

3. Calculate the moles of FeCl2 formed:
Since the stoichiometric ratio from the balanced equation tells us that 1 mole of Fe reacts to form 1 mole of FeCl2, the moles of FeCl2 will be the same as the moles of Fe.

4. Calculate the heat liberated using the given value of ΔH°:
Heat liberated = Moles of FeCl2 x ΔH°

Follow these steps, and you will find the value of heat liberated during the reaction.