What is always true of a combustion reaction?

carbon dioxide will be produced

the reaction absorbs energy

oxygen gas must be one of the reactants

one reactant must contain carbon

answer: oxygen gas must be one of the reactants

explanation: combustion reaction is a reaction in which a substance burns in the presence of oxygen to give large amounts of energy.

a) carbon dioxide is produced when hydrocarbons undergo combustion reaction.

b) combustion reactions are almost always accompanied by release of energy, they are exothermic reactions.

c) combustion takes place in the presence of molecular oxygen which is present in gaseous form   thus oxygen gas must be one of the reactants

d) it is not necessary. even inorganic compounds undergo combustion.

the product of the pressure and volume is also constant

water and alcohols have similar properties because water molecules contain hydroxyl groups that can form hydrogen bonds with other water molecules and with alcohol molecules, and likewise alcohol molecules can form hydrogen bonds with other alcohol molecules as well as with water.