Question

What is a formation reaction? What is standard heat of formation? [2] What is a combustion reaction? What is standard heat of combustion?

Answer 1

Answer:

What is a formation reaction? it is when a mol of a product it is formed from its elements constituents

What is standard heat of formation? the standard heat of formation or formation enthalpy,  it is the amount of energy necessary for produce a mol of the product when its elements constituent react.

What is a combustion reaction? It is when a hydrocarbon reacts with oxygen and produce water a carbon dioxide  

What is standard heat of combustion? It is the amount of energy released during a combustion reaction, measuring per mass or volume unit

Explanation:

A example of formation reaction is:

2H2 + O2 =2H2O

I hope my answer can help you

Answer 2

Answer:

- It is the amount of energy released or absorbed when a substance is formed by a synthesis chemical reaction.

- Reaction in which a fuel is burned with oxygen to yield water and carbon dioxide (among others).

- It is the amount of energy released when a fuel is burned.

Explanation:

Hello,

1. Standard heat of formation is understood as the involved energy, say absorbed or released, when a chemical compound is formed at STP conditions. For instance, formation of water:

$2H_2(g)+O_2(g)-->2H_2O(g)$

Releases 286kJ per 1 mole of formed water, that is why its standard heat of formation is $\Delta _fH^o_{H_2O}=-286kJ/mol$.

2. Combustion chemical reactions consist on the reaction between a fuel, usually a hydrocarbon, and oxygen to yield carbon dioxide and water was shown below, for example, for ethane:

$C_2H_6+\frac{7}{2} O_2-->2CO_2+3H_2O$

3.  Standard heat of combustion is understood as the involved energy, surely released, when a fuel is burned with oxygen at STP conditions. For instance, for the aforesaid combustion of ethane the standard enthalpy of combustion has a value of $\Delta _cH^o_{C_2H_6}=1560 kJ/mol$

Best regards.