7.1 Equilibrium constants  (Page 6/14)

Explain why there may be an infinite number of values for the reaction quotient of a reaction at a given temperature but there can be only one value for the equilibrium constant at that temperature.

Explain why an equilibrium between Br ₂ ( l ) and Br ₂ ( g ) would not be established if the container were not a closed vessel shown in [link] .

If you observe the following reaction at equilibrium, is it possible to tell whether the reaction started with pure NO ₂ or with pure N ₂ O ₄ ?
$2{\text{NO}}_2(g)\rightleftharpoons {\text{N}}_2{\text{O}}_4(g)$

Among the solubility rules previously discussed is the statement: All chlorides are soluble except Hg ₂ Cl ₂ , AgCl, PbCl ₂ , and CuCl.

(a) Write the expression for the equilibrium constant for the reaction represented by the equation $\text{AgCl}(s)\rightleftharpoons {\text{Ag}}^{\text{+}}(aq)+{\text{Cl}}^{\text{−}}(aq).$ Is K _c >1,<1, or ≈ 1? Explain your answer.

(b) Write the expression for the equilibrium constant for the reaction represented by the equation ${\text{Pb}}^{\mathrm{2+}}(aq)+2{\text{Cl}}^{\text{−}}(aq)\rightleftharpoons {\text{PbCl}}_2(s).$ Is K _c >1,<1, or ≈ 1? Explain your answer.

Among the solubility rules previously discussed is the statement: Carbonates, phosphates, borates, and arsenates—except those of the ammonium ion and the alkali metals—are insoluble.

(a) Write the expression for the equilibrium constant for the reaction represented by the equation ${\text{CaCO}}_3(s)\rightleftharpoons {\text{Ca}}^{\mathrm{2+}}(aq)+{\text{CO}}_3{}^{\text{−}}(aq).$ Is K _c >1,<1, or ≈ 1? Explain your answer.

(b) Write the expression for the equilibrium constant for the reaction represented by the equation $3{\text{Ba}}^{\mathrm{2+}}(aq)+2{\text{PO}}_4{}^{\mathrm{3-}}(aq)\rightleftharpoons {\text{Ba}}_3{\left({\text{PO}}_4\right)}_2(s).$ Is K _c >1,<1, or ≈ 1? Explain your answer.

Benzene is one of the compounds used as octane enhancers in unleaded gasoline. It is manufactured by the catalytic conversion of acetylene to benzene: $3{\text{C}}_2{\text{H}}_2(g)⟶{\text{C}}_6{\text{H}}_6(g).$ Which value of K _c would make this reaction most useful commercially? K _c ≈ 0.01, K _c ≈ 1, or K _c ≈ 10. Explain your answer.

Show that the complete chemical equation, the total ionic equation, and the net ionic equation for the reaction represented by the equation $\text{KI}(aq)+{\text{I}}_2(aq)\rightleftharpoons {\text{KI}}_3(aq)$ give the same expression for the reaction quotient. KI ₃ is composed of the ions K ⁺ and ${\text{I}}_3{}^{\text{−}}.$

For a titration to be effective, the reaction must be rapid and the yield of the reaction must essentially be 100%. Is K _c >1,<1, or ≈ 1 for a titration reaction?