In the given reaction,
X+Y+3 Z ⇄ X YZ₃
if one mole of each of X and Y with 0.05 mol of Z gives compound X Y Z₃. (Given : Atomic masses of X, Y and Z are 10, 20 and 30 amu, respectively.) The yield of X YZ₃ is _____________ g. (Nearest integer)

Solution

Chemistry ma’am · 4 steps

Z is needed three at a time and you have only 0.05 mol of it, so Z runs out first and fixes the yield.

1. Find the limiting reagent. One X and one Y each need three Z. To use up 1 mol of X you would need 3 mol of Z, but only 0.05 mol is there. So Z is the limiting reagent, and X and Y are in large excess.
2. Moles of product. Three moles of Z give one mole of XYZ₃. So 0.05 mol of Z gives 0.05/3 mol of XYZ₃.
3. Molar mass. XYZ₃ = 10 + 20 + 3 × 30 = 120 g mol⁻¹.

   m = 0.05/3 × 120 = 0.05 × 40 = 2 g

4. So. The yield of XYZ₃ is 2 g.

The common slip: 6. Forgetting the coefficient 3 on Z and taking 0.05 mol of product gives 0.05 × 120 = 6 g, not 2.

The idea to keep. Divide each reactant's moles by its coefficient. The smallest result is the limiting reagent, and that number is also the moles of product formed.

Answer from the NTA final answer key. Solution by PrepWiser.