This equation indicates that the reaction gives off heat. what is this type of reaction called? 2c4h10 +? o2 ? 8co2 + 10h2o + heat
a. an exothermic reaction
b. an endothermic reaction
c. absorption reaction
d. precipitation reaction

The answer to your question is letter a. exothermic reaction.

Explanation:

a. an exothermic reaction  An exothermic reaction is a reaction that gives off heat, so this option is correct.

b. an endothermic reaction An endothermic reaction is a reaction that absorbe energy from the surroundings so this option is wrong.

c. absorption reaction  It's a reaction similar to an endothermic reaction so is not the right answer

d. precipitation reaction It's another kind of reaction where one of the products precipitate, this option is incorrect.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.