How can you tell if rxn is combustion, formation, or bond energy?

[kirsten clemente 1E]

Hello,

I was on question 6 of Achieve Week 3&4 assignment, and I saw there are 3 different types of end products (combustion, formation, and bond energy?)

My first question is, are those three the only types of end products that can happen?

Also, I know that combustion always results in CO2 and H2O. But how can I tell if a reaction is a formation or bond change?

Thanks :)

[Katie_Vaca_2B]

hi!
I'm not sure about your first question, but for the second question, I know that the reaction is formation when the reactants are both pure and the elements are in their standard states. Also, there must be a single product with no coefficients. The reaction is bond energy only when the reaction breaks bonds without forming other bonds in the process.
For example, in the reaction C(g) + 4H(g) --> CH4(g), the reaction is the -4 x the bond energy of C-H.
I hope this helps :)

[Jess Max 2F]

hi!
I'm not sure about your first question, but for the second question, I know that the reaction is formation when the reactants are both pure and the elements are in their standard states. Also, there must be a single product with no coefficients. The reaction is bond energy only when the reaction breaks bonds without forming other bonds in the process.
For example, in the reaction C(g) + 4H(g) --> CH4(g), the reaction is the -4 x the bond energy of C-H.
I hope this helps :)

What does it mean for the reactants to be pure and in their element's standard states? Also, you said that formation is only when there is a single product with no coefficients; is this including the Co2 and H2o or not including them as products? Hope this makes sense.

[Katie_Vaca_2B]

hi!
I'm not sure about your first question, but for the second question, I know that the reaction is formation when the reactants are both pure and the elements are in their standard states. Also, there must be a single product with no coefficients. The reaction is bond energy only when the reaction breaks bonds without forming other bonds in the process.
For example, in the reaction C(g) + 4H(g) --> CH4(g), the reaction is the -4 x the bond energy of C-H.
I hope this helps :)

What does it mean for the reactants to be pure and in their element's standard states? Also, you said that formation is only when there is a single product with no coefficients; is this including the Co2 and H2o or not including them as products? Hope this makes sense.

For an element to be in their standard state, they would have to be in the form they take at a temp of 25 C and a pressure of 1 atm. For the reactants to be pure, it would simply mean they are not mixed compounds; they are of the same element such as H₂. Producing CO₂ and H₂O I think would be from combustion, not formation. In formation, there would be only one compound for a product. Correct me if I'm wrong, but I hope that makes sense !