Question

9. The following equilibrium is endothermic. In the box below, show how the reaction will shift response to the indicated stress by writing →., or no shift. 30,(8) 203(g) Stress Equilibrium shift? Increase O2 concentration Add heat Add a catalyst Cool reaction

Answer 1

Given equilibrium reaction is endothermic, hence we can write equation as shown below.

3 O ₂ (g) + Heat $\rightleftharpoons$ 2 O ₃ (g)

Now, by applying Le-chateliars principle we can solve given problem.

According to this principle, when reactant is added to equilibrium reaction or one of the product is removed , equilibrium disturbs and to attain equilibrium reaction proceeds in forward direction.

In this case , oxygen and heat are reactants, hence addition of them shift reaction to the product side ( i e right side)

According to this principle, when product is added to equilibrium reaction or reactant is removed, equilibrium disturbs and to attain equilibrium reaction proceeds in backward direction.

in this case , addition of O ₃ or removal of heat will shift reaction to left side.

Catalyst does not affect position of equilibrium

Stress	Equilibrium shift ?
Increase O 2 concentration	$\rightarrow$
Increase O 3 concentration	$\leftarrow$
Add heat	$\rightarrow$
Catalyst	No Shift
Cool reaction	$\leftarrow$

PART 2

Consider given reaction , C₆H₆ (l) + Br ₂ (l) $\rightarrow$ C₆H₅Br (l) + HBr (g)

From reaction, 1 mol C₆H₆$\equiv$ 1 mol Br ₂$\equiv$ 1 mol  C₆H₅Br $\equiv$ 1 mol HBr

To find limiting reactant we must know molar mass of both reactants.

Molar mass of benzene ( C₆H₆ ) = ( 6 $\times$ 12.01 ) + ( 6 $\times$ 1.0079 ) = 78.11 g / mol

Molar mass of Br ₂ = ( 2 $\times$ 79.91 ) = 159.82 g / mol

We have , 1 mol C₆H₆$\equiv$ 1 mol Br ₂

i e 78.11 g C₆H₆$\equiv$ 159.82 g Br ₂

$\therefore$ 40 g  C₆H₆$\equiv$ 159.82 $\times$ 40 / 78.11 g Br ₂

$\therefore$ 40 g  C₆H₆$\equiv$ 81.84 g  Br ₂

40 g benzene will require 81.84 g Br ₂ . The provided amount of Br ₂ is 125 g. Hence, it is excess reactant.

Therefore, benzene is limiting reactant .

ANSWER : Limiting reactant : Benzene