For the reaction of carbon dioxide to form carbon monoxide and oxygen, ah is equal
+570 kj. the reaction is
a. exothermic
b. combination
c. oxidation
d. endothermic
e. all of the above

d = endothermic

Explanation:

Chemical equation:

2CO₂  →  2CO + O₂

When carbon dioxide form carbon monoxide and oxygen the ΔH is +570KJ.

When enthalpy of reaction is positive and  ΔH is greater than zero it means heat is given to the reaction.

It is called endothermic reaction.

In this case enthalpy of product is higher than enthalpy of reactant

When enthalpy of reaction is negative and  ΔH is less than zero it means heat is released during the reaction.

It is called exothermic reaction.

In this case enthalpy of product is lower than enthalpy of reactant.

It is both a combustion reaction and a reduction reaction

Explanation:

Let us look closely at what a combustion reaction is. A combustion reaction is a reaction in which a substance combines with oxygen to produce heat and light. The process is exothermic.

We can see that the combination of zinc and oxygen above produced heat and light hence the process is a combustion reaction according to definition.

The bone of contention however is whether it is also a reduction reaction.

Now consider the changes in oxidation number from left to right.

Zn - 0 to +2

O - 0 to -2

We can see that Zn was oxidized and O was reduced. The process is also a reduction reaction since O experienced a negative change in oxidation number.

Be reminded that oxidation and reduction processes are always simultaneous.