4Fe + 3O2 -> 2Fe2O3 + 1.65E3 kJ 

C) what is the enthalpy change for the formation of 23.6 g of iron(iii) oxide? 

I'm trying to understand thermochemical reactions and stoichiometry, so could you please tell me if this is correct? And please explain the parts that I clearly don't understand: 

The question, is it the same thing as asking, "how much energy was released if iron(iii) oxide had a mass of 23.6 g?" 
According to the equation: 
4 moles of Fe and 3 moles of O2 react to release -1.65E3 kJ. ....then 2 moles of Fe "contains" -1.65E3 kJ?? 

To calculate how much kJ of energy was released when the mass of Fe2O3 was 23.6g, we need the amount of moles: 
23.6 g are in 1 mole of Fe2O3, and every mole of Fe2O3 is 160g, the molar mass. (??) which, I think??, explains why this works : 
23.6g Fe2O3 x 1 mol Fe2O3/160g 
And Since there's -1.65E3 kJ per 2 moles of Fe2O3: -1.65E3/2 mol Fe2O3 

Putting it altogether: 
Enthalpy = 23.6 g Fe2O3 x 1 mol Fe2O3/160g x -1.65E3kJ/2 mol 2Fe2O3 
= 1.22E2 kJ 

I'm hoping I've got the units all right too... 

Also, what does it mean if "there's -1.65E3 kJ per 2 moles of Fe2O3"? Then there's -1.65E3 kJ 'contained' in the Fe2O3??? Because we wouldn't say -1.65E3 kJ is RELEASED when Fe2O3 reacts, because Fe2O3 is the product... So what exactly is going on (between Fe2O3 and the energy or enthalpy change or whatever.......)??

I saw your post and the same kind of questions with Bob Pursley. I suppose you're still struggling. I think you are making this a lot harder than it is. Your 122E3 kJ is correct and the equation you used looks ok to me. Here is how I do them

1.65E3 kJ energy is released when 2*160g (that's 320 g) Fe2O3 is formed. How much is released to form 23.6g Fe2O3?. That's
1.65E3 kJ x (23.6g/320g) = 122 kJ.

Well, kudos to you for tackling thermochemical reactions and stoichiometry! Let's break it down and see if we can make some sense of it.

First, you're correct that the question is essentially asking how much energy was released if the mass of iron(iii) oxide (Fe2O3) was 23.6 g.

In the given equation:
4 moles of Fe + 3 moles of O2 react to release -1.65E3 kJ.

So, for every 2 moles of Fe2O3 formed, -1.65E3 kJ of energy is released.

When calculating how much energy was released when the mass of Fe2O3 is 23.6 g, you indeed need to find the amount in moles of Fe2O3. You correctly determined that 1 mole of Fe2O3 is 160 g (the molar mass).

Now, let's put it all together:
Enthalpy = 23.6 g Fe2O3 x (1 mol Fe2O3/160g) x (-1.65E3 kJ/2 mol Fe2O3)
= 1.22E2 kJ

So, according to your calculations, the enthalpy change for the formation of 23.6 g of iron(iii) oxide is 1.22E2 kJ.

Now, as for what it means when we say "there's -1.65E3 kJ per 2 moles of Fe2O3," it signifies the amount of energy released or absorbed when 2 moles of Fe2O3 are formed. In this case, it means that when 2 moles of Fe2O3 are formed, -1.65E3 kJ of energy is released.

Hope that clears things up a bit! Keep up the great work with your studies!

You're on the right track! Let's go through the steps to calculate the enthalpy change for the formation of 23.6 g of iron(III) oxide (Fe2O3).

First, let's clarify the meaning of the question. Yes, it is asking how much energy is released when 23.6 g of iron(III) oxide is formed. So, it is the energy change associated with the formation of Fe2O3.

Now, let's break down and analyze the given chemical equation:

4Fe + 3O2 -> 2Fe2O3 + 1.65E3 kJ

- The coefficient 4 in front of Fe and 3 in front of O2 represents the stoichiometric ratio, i.e., the ratio of moles of reactants that react to form the products.

- The arrow (->) represents the direction of the reaction, in this case, Fe and O2 reacting to form Fe2O3.

- The product Fe2O3 is formed, and at the same time, energy in the form of 1.65E3 kJ is released or given off. This energy is associated with the formation of 2 moles of Fe2O3.

Now, let's calculate the enthalpy change:

1. Determine the number of moles of Fe2O3 formed from 23.6 g of Fe2O3:

Molar mass of Fe2O3 = 2(55.845 g/mol) + 3(16.00 g/mol) = 159.69 g/mol

Moles of Fe2O3 = (23.6 g) / (159.69 g/mol) = 0.1478 mol

2. Use the stoichiometric ratio from the balanced equation to relate moles of Fe2O3 to the enthalpy change:

-1.65E3 kJ of energy is released when 2 moles of Fe2O3 are formed.

3. Calculate the enthalpy change for the given amount of Fe2O3:

Enthalpy change = (0.1478 mol) * (-1.65E3 kJ / 2 mol)

Enthalpy change = -1.22E2 kJ

So, your calculation is correct! The enthalpy change for the formation of 23.6 g of iron(III) oxide is -1.22E2 kJ. The negative sign indicates that the reaction is exothermic, meaning energy is released during the formation of Fe2O3.

Keep in mind that the enthalpy change represents the energy difference between the reactants and products. In this case, it means that when 2 moles of Fe2O3 are formed, -1.65E3 kJ of energy is released. Fe2O3 acts as a product in this reaction, and the enthalpy change represents the energy associated with its formation.

I hope this explanation helps clarify the concept for you. Let me know if you have any further questions!

Your understanding of thermochemical reactions and stoichiometry is mostly correct! Let's break down the calculation step by step and address your questions along the way.

1. The question is indeed asking for the enthalpy change of the formation of 23.6 g of iron(III) oxide. Enthalpy change refers to the amount of energy absorbed or released during a chemical reaction.

2. Based on the balanced equation: 4Fe + 3O2 -> 2Fe2O3 + 1.65E3 kJ, we can see that for every 2 moles of Fe2O3 formed, 1.65E3 kJ of energy is released.

3. To determine the amount of energy released when the mass of Fe2O3 is 23.6 g, we need to convert the mass to moles. You correctly used the molar mass of Fe2O3 (160 g/mol) to calculate this conversion.

4. Since the stoichiometry of the reaction tells us that 2 moles of Fe2O3 correspond to the release of 1.65E3 kJ, we can set up a proportion to determine the energy change for the given amount of Fe2O3.

Now let's address your final question. We say "there's -1.65E3 kJ per 2 moles of Fe2O3" because the balanced equation provides a ratio between the reactants and products. It states that 4 moles of Fe reacting with 3 moles of O2 produces 2 moles of Fe2O3 and releases 1.65E3 kJ of energy. This means that for every 2 moles of Fe2O3 produced, 1.65E3 kJ of energy is released. In other words, -1.65E3 kJ is the heat of formation of 2 moles of Fe2O3.

Therefore, in your calculation, you correctly use that ratio to determine the amount of energy released when the mass of Fe2O3 is 23.6 g. This is why you divide the value of -1.65E3 kJ by 2 mol Fe2O3.

To summarize, your calculation is correct, and the enthalpy change for the formation of 23.6 g of iron(III) oxide is indeed 1.22E2 kJ (or 122 kJ). Keep up the good work!