Question

What is the limiting reactant in a chemical reaction?

Answer 1

Answer:

D.) the reactants that runs out first

Explanation:

Limiting reactant is the reactant which is present in the smallest amount and thus limit the yield of product.

In any chemical reaction limiting reactant is identified by steps:

First we will calculate the number of moles of given amount of reactants.

Then we will find the number of moles of product by comparing with moles of reactant through balanced chemical equation.

Then we will identified the reactant which produced smaller amount of product.

It can be better understand by following problem.

Given data:

Mass of calcium carbonate = 25 g

Mass of hydrochloric acid = 13.0 g

Mass of calcium chloride produced = ?

Which is limiting reactant= ?

Chemical equation:

CaCO₃ + 2HCl  → CaCl₂  + H₂O + CO₂

Number of moles of CaCO₃:

Number of moles of CaCO₃ = Mass /molar mass

Number of moles of CaCO₃= 25.0 g / 100.1 g/mol

Number of moles of CaCO₃ = 0.25 mol

Number of moles of HCl:

Number of moles of HCl = Mass /molar mass

Number of moles of HCl = 13.0 g / 36.5 g/mol

Number of moles of HCl = 0.36 mol

Now we will compare the moles of CaCl₂ with HCl and CaCO₃ .

                   CaCO₃         :               CaCl₂

                       1               :               1

                     0.25           :            0.25

                   HCl              :                CaCl₂

                     2                :                 1

                   0.36            :               1/2 × 0.36 = 0.18 mol

The number of moles of CaCl₂ produced by HCl are less it will be limiting reactant.

Mass of calcium chloride:

Mass of CaCl₂ = moles × molar mass

Mass of CaCl₂ =0.18 mol × 110.98 g/mol

Mass of CaCl₂ =  20 g