What is copper + magnesium sulfate?
You are asking what the reaction between copper and magnesium sulfate produces. Actually, adding copper metal to an aqueous solution of magnesium sulfate will produce no reaction. Nothing will change. That is because magnesium is a more reactive metal than copper. There is a metal reactivity series based on the naturally occurring reactivity potentials of the metals on the periodic table. This series is referenced in the link below. Copper is one of the least reactive metals and magnesium is one of the more reactive metals. So adding magnesium metal to copper sulfate will produce a chemical reaction (the metal will slowly dissolve as it ionizes), but adding copper metal to magnesium sulfate will produce no reaction (the copper metal will simply sit in solution).