Multiple choice chemistry mix and separate different types of mixtures homogenous and heterogenous mixtures all about mixtures Which one of the following statement is incorrect? All elements are homogeneous Compound made up of a number of elements are heterogeneous A mixture is not always heterogeneous Air is a heterogeneous mixture Reveal answer Fill a bubble to check yourself D Correct answer Explanation Air is a mixture of gas in gas.The mixture of gas in gas is always homogenous.Thus, air is a homogenous mixture.