In the reaction MgCl2 + 2KOH Mg (OH) 2 + 2KCI, if 3 moles MgCh are added to 4 moles KOH, what determines how much Mg (OH) 2 is made?

Answer:-

KOH determines how much Mg (OH) 2 is made.

2 mol of Mg (OH) 2 formed

Explanation:-

The balanced equation is

MgCl2 + 2KOH - -> Mg (OH) 2 + 2KCI,

From seeing the coefficients we notice

2 mol of KOH reacts with 1 mol of MgCl2

4 mol of KOH reacts with 1 x 4 / 2 = 2 mol of MgCl2

3 moles of MgCl2 was added but only 2 mol react.

So we see there is excess MgCl2.

Hence KOH is the limiting reactant.

So KOH determines how much Mg (OH) 2 is made.

We see from the balanced chemical equation,

2 mol of KOH gives 1 mol of Mg (OH) 2.

4 mol of KOH will give 1 x 4 / 2 = 2 mol of Mg (OH) 2.