Chemistry is my worst subject

Question

Magnesium reacts with iodine gas at high temperatures to form magnesium iodide, 2Mg + I₂ à MgI₂

a, What mass of MgI₂ can be produced from the reaction of 5.15 g Mg and 11.7 g I₂?  Answer:     grams MgI₂ (Round your answer to the nearest tenths)

b. Which reactant is the limiting reactant, Mg or I₂?    is the limiting reactant

Answer 1

First, omit the "2" to get a balance reaction Mg + I₂ --> MgI₂.

a) For first reactant, (5.15g Mg) * (1 mol Mg / 24.3 g Mg) * (1 mol MgI₂ / 1 mol Mg) = 0.212 mol MgI₂.

For second reactant, (11.7g I₂) * (1 mol I₂ / 507.6g I₂) * (1 mol MgI₂ / 1 mol I₂) = 0.02305 mol MgI₂.

Mass of product is determined by moles of I₂, (0.02305 mol MgI₂) * (531.9g MgI₂ / 1 mol MgI₂) = 12.3g MgI₂.

b) Already determined for completing part a, iodine is the limiting reactant.