How many moles of magnesium chloride are produced when 4.39 moles of magnesium are placed in a beaker containing only 250.0 grams of hydrochloric acid?

Explanation:

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In this case, since the reaction between magnesium and hydrochloric acid is:

Whereas there is a 1:1 and 1:2 mole ratio between magnesium and magnesium chloride and hydrochloric acid and magnesium chloride respectively; it is possible to compute the yielded moles of product by each reactant and then determine which moles are correct based on the limiting reactant; therefore, we proceed as follows:

Thus, since the hydrochloric acid yields the fewest moles of product, we infer it is the limiting reactant, so the correct number moles of magnesium chloride are 3.43 mol.

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n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

the answer would be b i believe