250.0 mg solid magnesium placed in 9.1 g aqueous zinc nitrate... What is the limiting reagent?

Question

I balanced the equation:
Mg (s) + 2HNO3 (aq) -> Mg(NO3)2 (aq) + H2 (g)
250 mg 9.1 g

Answer 1

You may have balanced the equation but it's the wrong equation.
Mg + Zn(NO3)2 ==> Mg(NO3)2 + Zn

I do these the long way.
mols Mg = grams/molar mass = ?
mols Zn(NO3)2 = grams/molar mass = ?

Using the coefficients in the balanced equation, convert mols Mg to mols of either product.
Do the same and convert mols Zn(NO3)2 to mols of the same product.
It is likely that these two values will not agree; the correct value in limiting reagent problems is ALWAYS the smaller value and the reagent producing that value is the limiting reagent.