Question

Sodium and water react according to the reaction 2Na(s) + 2H2O(l) ® 2NaOH(aq) + H2(g) What number of moles of H2 will be produced when 4 mol Na is added to 2 mol H2O? a 1 mol b 2 mol c 3 mol d 4 mol e none of these

Determine the limiting reactant when 4.00 mol of Sb are reacted with 5.00 mol Cl₂ according to the unbalanced equation

Sb + Cl₂ ® SbCl₃

  

a Sb

  

b Cl₂

  

c Cl

  

d SbCl₃

  

e no limiting reactant

Answer 1

Limiting reagent = reagent present in lesser quantity than needed for both reactants to completely react. Theoretical yield is calculated considering that the limiting reagent has reacted completely.

Question 1

Balanced reaction:

2 Na (s) + 2 H₂O(l) = 2 NaOH (aq) + H₂ (g)

From the balanced equation, 2 mole Na needs 2 moles H₂O

Thus, 4 moles Na needs = 4 moles H₂O.

However, the number of moles of H₂O taken is less than what is needed for the 4moles of Na to completely react. So, H₂O is the limiting reagent.

So, amount of product formed depends upon the moles of H₂O reacting.

From the balanced equation, 2 mole H₂O gives 1 moles H₂.

Hence, 1 mole of H₂ is produced ( option a)

Question 2.

Balanced equation :

2 Sb + 3 Cl₂ = 2 SbCl₃

From the balanced equation, 2 mole Sb needs 3 moles Cl₂

Thus, 4 moles Sb needs = 6 moles Cl₂.

However, the number of moles of Cl₂taken is less than what is needed for the 4moles of Sb to completely react. So, Cl₂ is the limiting reagent.