Question

Identify the limiting reactant in the reaction of hydrogen and ethylene (c2h4) to form c2h6, of 4.40 g of h2 and 10.5 g of c2h4 are combined. Determine the amount (in grams) of excess reactant that remains after the reaction is complete.

Answer 1

Definition :   Limiting reagent is the substance in a chemical reaction that is consumed when chemical reaction is complete.

step 1 :  first write the chemical reaction and then balanced the chemical equation

$C_{2}H_{4} + H_{2} \rightarrow C_{2}H_{6}$

step 2 :  convert given masses into moles.

$\text{ moles of } C_{2}H_{4}=10.5 (g)/ 28 (\text{ g/mole)} = 0.375 \text{ moles}$

$\text{moles of }H_{2}= 0.40 (g)/ 2 (g/mole) = 0.20 moles$

step 3 :  Now find the limiting reagent.

$\text{ moles of }C_{2}H_{4} \text{ in excess}= 0.375-0.20 = 0.175 \text{moles}$

Now we conclude that  $C_{2}H_{4}$ is the limiting reagent.

step 4 :  Amount of the excess reactant i.e $C_{2}H_{4}$

$\text{ mass of }C_{2}H_{4}= 0.175 (moles) \ast 28 (g/mole) = 4.9 g$