For N₂ + 3H₂ → 2NH₃, 28 g of N₂ is mixed with 4 g of H₂. What is the maximum mass of NH₃ that can form? (Relative atomic masses: H = 1, C = 12, N = 14, O = 16, Na = 23, Mg = 24, Al = 27, S = 32, Cl = 35.5, K = 39, Ca = 40, Fe = 56, Zn = 65.)

Answer and explanation

Correct answer: C. 22.667 g

  1. Step 1: There are 1 mol of N₂ and 2 mol of H₂; the ratio needed is 1 : 3, so the limiting reactant is H₂.
  2. Step 2: H₂ gives at most 1.333 mol of NH₃.
  3. Step 3: Mass = 1.333 x 17 = 22.667 g.
Answer
22.667 g.
Why not the others: 34 g: only N₂ was used, without checking whether the H₂ is enough. 32 g: the masses of the reactants were added. 11.333 g: the coefficient 2 was left out when converting to grams.

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