403RctnQuotient

403RctnQuotient - The reaction quotient Consider the...

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Lesson 18 1 Lesson 18 The reaction quotient Consider the general reversible chemical reaction ( not in chemical equilibrium ): a A + b B = c C + d D The initial concentrations of reactants and products are [A] init , [B] init , [C] init , and [D] init The reaction quotient for this reaction is defined by the equation: b init B a init A d init D c init C p b init a init d init c init c P P P P Q B A D C Q ; ] [ ] [ ] [ ] [ The definitions of Q c and Q p are analogous to the definitions of K c and K p but Q c and Q p are calculated for a set of non-equilibrium concentrations Lesson 18 Q c and direction of change • If Q c = K c : – Chemical equilibrium – Product and reactant concentrations do not change • If Q c < K c : – Reactants are in excess – Reactant concentrations will decrease and product concentrations will increase • If Q c > K c : – Products are in excess – Product concentrations will decrease and reactant concentrations will increase Lesson 18 Q c and direction of change
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Lesson 18 2 Lesson 18 Example 1 At elevated temperatures, NO 2 reacts with CO according to the reversible chemical equation: NO 2 ( g ) + CO ( g ) = NO ( g ) + CO 2 ( g ) NO 2 has a brownish colour. The other gases taking place in the reaction are colourless. When a gas mixture is prepared at 500 K, in which 3.4 atm is the initial partial pressure of both NO 2 and CO, and 1.4 atm is the partial pressure of both NO and CO 2 , the brown colour of the mixture is observed to fade as the reaction proceeds towards equilibrium. Give a condition that must be satisfied by the equilibrium
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This note was uploaded on 11/29/2011 for the course CHE 102 taught by Professor Simon during the Fall '08 term at Waterloo.

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403RctnQuotient - The reaction quotient Consider the...

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