[mudkip26]

Do the follow reactions depict Heat of Formation Reactions? If so, mark the reaction as YES, if it is not a Heat of Formation Reaction, then choose NO. My answers will be in blue:


 2Fe2O3(s)  4Fe(s) + 3O2(g) Yes
 C2H4(g) + 2O2(g)  2CO(g) + 2H2O(g) No
 H2(g) + 1/2O2(g)  H2O(g) No
 Ni(s) + 4CO(g)  Ni(CO)4(g) Yes
 Ca(s) + Cl2(g)  CaCl2(s) Yes


Remember: In formation reactions the reactants must be elements in their most common states, and the only product is one mole of the substance of interest.

I guess I might not be understanding something, but I don't know where I'm going wrong. :/

[Borek]

2Fe2O3(s)  4Fe(s) + 3O2(g) Yes

Remember: In formation reactions the reactants must be elements in their most common states, and the only product is one mole of the substance of interest.

List the reactants - do they fit the definition?

[mudkip26]

2Fe2O3(s)  4Fe(s) + 3O2(g) Yes

Remember: In formation reactions the reactants must be elements in their most common states, and the only product is one mole of the substance of interest.

List the reactants - do they fit the definition?

I'm guessing that they don't fit the definition. Is that the only one I have wrong?

[mudkip26]

2Fe2O3(s)  4Fe(s) + 3O2(g) Yes

Remember: In formation reactions the reactants must be elements in their most common states, and the only product is one mole of the substance of interest.

List the reactants - do they fit the definition?

Wait. All of the reactants do fit the definition of being in their most common states.

[Borek]

What is the difference between reagent and reactant?

[mudkip26]

What is the difference between reagent and reactant?

Reactants are the products that are in the beginning of the reaction. So, Fe2O3 would be the reactant for the first reaction.

[Borek]

Reactants are the products that are in the beginning of the reaction.

Ghjkdgs huioasdhjk hjkle?*

So, Fe2O3 would be the reactant for the first reaction.

Yes.

*Makes to me about as much sense as what you wrote Reactants are what you start with, products are what you end with, both reactants and products are reagents. As far as I know these definitions are not widely accepted as the only correct ones, and terms are often used interchangeably, but for this particular question it is important to be precise about these things.

[mudkip26]

Reactants are the products that are in the beginning of the reaction.

Ghjkdgs huioasdhjk hjkle?*

So, Fe2O3 would be the reactant for the first reaction.

Yes.

*Makes to me about as much sense as what you wrote Reactants are what you start with, products are what you end with, both reactants and products are reagents. As far as I know these definitions are not widely accepted as the only correct ones, and terms are often used interchangeably, but for this particular question it is important to be precise about these things.

I'm sorry about the first one. XD
Anyways, I'm just confused as to what the one mole of product plays at. Does that mean one mole of each product or all together for all products with each reaction?

[fledarmus]

Hey mudkip26,

You did what the forum rules required and tried to work your way through, but it is obvious you are missing the point of the question. Let's take a step back to the definition and try to work it through from the beginning -

Definition -

"In formation reactions the reactants must be elements in their most common states, and the only product is one mole of the substance of interest."

Going through these one at a time -
Reactants are the things that react. They are written on the left side of the reaction arrow.
Elements are substances that contain only one type of atom.

So already you can discard three of the reactions based on the reactants - the first one contains Fe2O3 which is not an element (contains both iron and oxygen), the second contains C2H4, which is not an element (contains both carbon and hydrogen), and the fourth contains CO, which is not an element (contains both carbon and oxygen).

their most common state - this phrase is modifying "elements" - the elements which are your reagents must be in their most common states. All of the reactions you show have the elements in their most common states, fortunately.

the only product - additional information to let you throw away the first and second reactions - they have more than one product. A heat of formation reaction only has one product.

one mole - the reaction must be balanced so that there is only one mole of your only one compound to give you the heat of formation.

So we've thrown out reactions 1, 2, and 4 so far - does that mean 3 and 5 are heat of formation reactions? Let's see...

in reaction 3, the reactants are hydrogen and oxygen. Both are elements, since they each contain only one type of atom, and both are in their most common state - diatomic gases. There is only one product, gaseous water, and only one mole of that product is shown in the balanced reaction. So yes, this is a Heat of Formation reaction, which will give you the Heat of Formation of H₂O(g).

In reaction 5, the reactants are calcium and chlorine - both elements. Calcium is a solid, chlorine is a diatomic gas - those are the most common forms of those elements. There is only one product, solid CaCl₂, and the equation is balanced to give one mole of the product. So yes, this is the Heat of Formation reaction for CaCl₂(s).

Now you need to find some others to practice on! Or better yet, find some compounds and practice writing out heat of formation reactions for them - that will prove more valuable in the long run.

Good luck!

[mudkip26]

Hey mudkip26,

You did what the forum rules required and tried to work your way through, but it is obvious you are missing the point of the question. Let's take a step back to the definition and try to work it through from the beginning -

Definition -

"In formation reactions the reactants must be elements in their most common states, and the only product is one mole of the substance of interest."

Going through these one at a time -
Reactants are the things that react. They are written on the left side of the reaction arrow.
Elements are substances that contain only one type of atom.

So already you can discard three of the reactions based on the reactants - the first one contains Fe2O3 which is not an element (contains both iron and oxygen), the second contains C2H4, which is not an element (contains both carbon and hydrogen), and the fourth contains CO, which is not an element (contains both carbon and oxygen).

their most common state - this phrase is modifying "elements" - the elements which are your reagents must be in their most common states. All of the reactions you show have the elements in their most common states, fortunately.

the only product - additional information to let you throw away the first and second reactions - they have more than one product. A heat of formation reaction only has one product.

one mole - the reaction must be balanced so that there is only one mole of your only one compound to give you the heat of formation.

So we've thrown out reactions 1, 2, and 4 so far - does that mean 3 and 5 are heat of formation reactions? Let's see...

in reaction 3, the reactants are hydrogen and oxygen. Both are elements, since they each contain only one type of atom, and both are in their most common state - diatomic gases. There is only one product, gaseous water, and only one mole of that product is shown in the balanced reaction. So yes, this is a Heat of Formation reaction, which will give you the Heat of Formation of H₂O(g).

In reaction 5, the reactants are calcium and chlorine - both elements. Calcium is a solid, chlorine is a diatomic gas - those are the most common forms of those elements. There is only one product, solid CaCl₂, and the equation is balanced to give one mole of the product. So yes, this is the Heat of Formation reaction for CaCl₂(s).

Now you need to find some others to practice on! Or better yet, find some compounds and practice writing out heat of formation reactions for them - that will prove more valuable in the long run.

Good luck!

Awesome! Thank you so much for your *delete me* (:
I understand it now.