Consider the following reaction: CrCl₃(s)+ KCl(s)+ 2H₂SO₄(l)→ KCr(SO₄)₂(s)+ 4HCl(g)green white colorless purple colorless solid solid liquid solid gas When the green solid is mixed with the white solid and the colorless liquid is added, the mixture starts to bubble and fume. When all action has stopped, a wet purple solid containing solid white specks remains. Which substance is the limiting reactant?

Question

Quizplus · Accepted Answer

To determine the limiting reactant, we need to compare the amount of moles of each reactant with the stoichiometric coefficients in the balanced equation. From the equation, we can see that 1 mole of CrCl3 is needed for 1 mole of KCr(SO4)2 to be produced. However, 1 mole of KCl is needed for 1 mole of KCr(SO4)2 to be produced, and 2 moles of H2SO4 are needed for 1 mole of KCr(SO4)2 to be produced. Therefore, we need to calculate the moles of each reactant present in the reaction mixture and compare it with the stoichiometric coefficients.

Let x be the moles of CrCl3, y be the moles of KCl, and z be the moles of H2SO4. Then, using the molar masses of each reactant:

x = 0.75 g / 158.36 g/mol = 0.004734 mol
y = 1 g / 74.55 g/mol = 0.013402 mol
z = 0.5 mL x 1 g/mL / 98.08 g/mol x 2 mol H2SO4 / 1 mol = 0.010153 mol

Now, we need to find the minimum of these values based on the stoichiometric coefficients in the balanced equation. From the balanced equation, we see that 1 mole of CrCl3 produces 1 mole of KCr(SO4)2, so x = 0.004734 mol of CrCl3 will produce 0.004734 moles of KCr(SO4)2. However, 1 mole of KCl produces 1 mole of KCr(SO4)2, so y = 0.013402 mol of KCl will produce 0.013402 moles of KCr(SO4)2. Lastly, we need to consider the amount of H2SO4 present. Since 2 moles of H2SO4 are needed to produce 1 mole of KCr(SO4)2, we can only produce a maximum of 0.0050765 moles of KCr(SO4)2 from z = 0.010153 mol of H2SO4. Therefore, z is the limiting reactant.

Since z represents the moles of H2SO4 present, the answer is (C) H2SO4.

Consider the Following Reaction: CrCl3(s)+ KCl(s)+ 2H2SO4(l)→ KCr(SO4)2(s)+ 4HCl(g)green White

Consider the Following Reaction: CrCl₃(s)+ KCl(s)+ 2H₂SO₄(l)→ KCr(SO₄)₂(s)+ 4HCl(g)green White