What type of reaction is: ch4 + 2o2 → co2 + 2h2o + 218 kcal? an exothermic reaction a combination reaction a decomposition reaction an endothermic reaction a single replacement reaction?

An exothermic reaction.

Explanation: The given reaction is a combustion reaction. Combustion is burning in presence of oxygen. Combustion of hydrocarbons in presence of oxygen produces carbon dioxide and water and a lots of amount of heat is released in these reactions.

If we take a look at the given equation then combustion of methane is taking place and 218 kcal heat is produced which indicates an exothermic reaction.

Now if we look at the answer choices then the only correct choice is first one that is an exothermic reaction.

In combination reactions two or more reactants react to produce a product. In decomposition reactions a compound breaks on heating into more than one products and the heat is required for this so decomposition is an endothermic reaction.

In single replacement reactions, one element is replaced by a compound by another element and these reactions looks as:

Hence, the only correct choice is en exothermic reaction.

geosphere and hydrosphere.

this is because the geosphere has to do with geological events, while the hydrosphere controls all water on earth.