Question

murease the number of moles of gas. 20. Consider the following reaction at equilibrium. W(s) + 6 HCI(E) → W ielk) + 3 H2(e) with AH = 60 kJ For each of the following changes, write in each blank box whether the amount of the corresponding species will "decrease", "increase", or remain unchanged" compared to the 'stressed state' HCI WCIS Stress a. Additional W is added to the reaction vessel (Assume the addition of the tungsten does not change the total pressure within the reaction vessel.) b. Most of WCI. is liquefied and withdrawn from the mixture. c. The volume of the reaction vessel decreases at constant temperature. d. The temperature of the reaction mixture is decreased

Answer 1

Stress		$WCl_6$	$H_2$
Solid reactant is added	unchanged	unchanged	unchanged
Product $WCl_6$ is removed	decrease	increase	increase
Volume is decreased	decrease	increase	increase
Decrease in temperature	increase	decrease	decrease

Addition of solid reactant/product does not affect the amounts of species as soldis do not appear in the equilibrium constant expression

When a product is removed, forward reaction produces more of it to nullify the effect of its removal. The amounts of reactants decrease and that of products increase.

With decrease in volume at constant temperaure, the pressure of system increases. The equilibrium shifts towards side with fewer number of moles of gaseous species. This is to minimize the effect of increase in pressure. There are 6 moles of gaseous reactants for 4 moles of gaseous products. Products have fewer number of moles of gaseous species than reactants. The equilibrium shifts towards products. The amounts of reactants decrease and that of products increase.

Positive sign of $\Delta H^o$ suggests endothermic reaction. Heat is absorbed during reaction.

$Reactants \ + \ heat \to \ products$

Decrease in temperature is removal of heat. Heat is a reactant.

When a reactant is removed, backward reaction produces more of it to nullify the effect of its removal. The amounts of reactants increase and that of products decrease.