Question

A -10.0 mL solution of 0.320 M KOH was mixed with 25.0mL of 0.120 M HBr solution. Which one is the limiting reagent, KOH or HBr? Explain!

Answer 1

volume of KOH, V = 10.0 mL

= 1*10^-2 L

we have below equation to be used:

number of mol in KOH,

n = Molarity * Volume

= 0.32*0.01

= 3.2*10^-3 mol

volume of HBr, V = 25.0 mL

= 2.5*10^-2 L

we have below equation to be used:

number of mol in HBr,

n = Molarity * Volume

= 0.12*0.025

= 3*10^-3 mol

we have the Balanced chemical equation as:

KOH + HBr ---> KBr + H2O

1 mol of KOH reacts with 1 mol of HBr

for 0.0032 mol of KOH, 0.0032 mol of HBr is required

But we have 0.003 mol of HBr

so, HBr is limiting reagent