What's the difference between homogeneous and heterogeneous mixtures?

Calculate the mass of silver needed to react with chlorine to produce 126g if silver chloride?

Calculate the number of moles of ethane in 100 grams

Consider the following reactions. (note: (s) = solid, (l) = liquid, and (g) = gas.) mg(s) + ½o2(g) → mgo(s) + 146 kcal/mole h2(g) + ½o2(g) → h2o(g), δh = -57.82 kcal/mole what type of reaction is represented by the previous two examples?