CHE 1302 Study Guide - Quiz Guide: Endothermic Process, Stoichiometry, Ideal Gas Law

ENT ives To determine equilibrium concentrations for species in solution . Examine temperature effects on reaction equilibrium Investigate the shift in equilibrium from different stresses on a system kills . Use colorimeter to determine unknown solution concentrations ced .Preparing temperature baths to change reaction conditions tionEquilibrium is defined as a state in which the concentrations of both the reactants and products have no tendency to change with time. We can restate this by saying that the rate of the forward reaction is equal to the rate of the reverse reaction. Recall that with rate we are simply defining how fast a reaction is proceeding, a speed at which the reaction proceeds. Take note that when writing an equilibrium expression, pure liquids (denoted by l or 2) and pure solids (denoted by s) are omitted. Typically we express the equilibrium by K or Kp where c and p denote either concentration or partial pressure respectively. We refer to this value of K, or Kp as an equilibrium constant For any reaction, Kc can be written as the product of the concentration of products, raised to their stoichiometric coefficients, divided by the product of the concentration of the reactants raised to their stoichiometric coefficients. See Equation (5-1) below for an example: aA(aq) + bB(aq-cC(aq) + dD(aq) (5-1) A] [B]b As mentioned before, K, or K, are equilibrium constants meaning that they will have the same value unless temperature is changed. This brings in two important ideas 1) We can perturb the equilibrium concentrations of a reaction, say [A] for instance which will cause the other concentrations to shift so that K for the reaction remains constant. 2) If we change temperature, we will either increase or decrease our value of K depending on the specific reaction we are examining. Determining K, and Equilibrium Concentrations During lecture we often discuss the idea of using ICE tables as a method for organizing and calculating concentrations of reactions as they proceed towards equilibrium. In a typical ICE table you need to know initial concentrations and the magnitude of K to determine the equilibrium concentrations. Alternatively, if you know the equilibrium concentrations for a reaction you can calculate K. For this experiment we will be examining a complex ion formation, when iron(III) ion

1. For each of the following statements describing equilibrium, clearly mark T for true or F for false All chemical reactions can proceed, in principle, in the reverse direction. Once equilibrium has been reached, reactant species no longer react to give products. For a system at equilibrium, the rates of the forward and reverse reactions are equal. For a system at equilibrium, concentrations of the products and reactants are equal. Chemical Reactions always proceed toward equilibriunm. There is no observable change in a chemical system at equilibrium. All chemical reactions are product-favored at equilibrium. 2. Consider the reaction of hydrogen gas with nitrogen gas producing ammonia, NH. Give the balanced chemical equation. How many moles of ammonia are formed from one mole of nitrogen? How many moles of nitrogen are required to react with one mole of hydrogen? 3. Solve for x. Show all work. 16 = (1-x)2 1.8 x 100.0010-x

Nams: correct answer on Multiple choice, each question is worth 4 points Write the letter to the co 1. Which of the following is true about a system at equilibrium? ) The concentration(s) of the reactants) is equal to the concentration(s) of the productts) B) No new product molecules are formed The rate of the reverse reaction is equal to the rate of the forward reaction and both rates are equal to zero C) The concentration(s) of reactantís) is constant over time. D) E) None of the above (A-D) are true 2. Equilibrium is reached in chemical reactions when: A) the rates of the forward and reverse reactions become equal. B) the concentrations of reactants and products become equal. C) the temperature shows a sharp rise O) all chemical reactions stop. E) the forward reaction stops. Vhich expression correctly describes the equilibrium constant for the following reaction? K-(4[CO2l+2H20]1)/(2[C2H2]+5[O2]) K = ( [CO2][H2O] ) / ( [C2H2][O2] ) der the chemical system Co+ Ch coCh: K-4.6 x 10 L/mol. centration of the product were to double, what would happen to the equilibrium constant? ould double its value. ould become half its current value. uld quadruple its value. uld not change its value. ld depend on the initial conditions of the product. for A2 +2B2AB, then for 4AB 2A2+4B, K would equal: n NO(g) + ½Odg,--NO2(g) at 750°C, the equilibrium constant Kc equals: