Chemistry 30: equilibrium Part 3 Ice box

ICE Box Problems [HI] [H2] [I2] Initial Change Equilibrium Example: At 430°C the Keq for the following reaction is 1.84 × 10-2. 2 HI(g) ⇌ H2(g) + I2(g) If 0.100 mol of hydrogen iodide is placed in a 1.00 L container and allowed to reach equilibrium at this temperature, find the concentrations of all the species at equilibrium. Keq= ICE Box Problems: To fill in an ICE box, we write the initial concentrations of all species in the first row. We use the balanced equation to determine the values in the middle ‘change’ row. In this example, for every two moles of HI that are used up, one mole of H2 and one mole of I2 are created. We let the change in concentration equal x. To find the values in the bottom ‘equilibrium’ row you add the ‘initial’ and ‘change’ values. Initial + Change = @ Equilibrium   [HI] [H2] [I2] Initial Change Equilibrium

ADD TO NOTES In a 3.0L container 0.69moles of N2 and 6.87 moles of H2 are allowed to reach equilibrium. At equilibrium the concentration of H2 is 1.91M. Calculate Keq for the following reaction: N2+ H2 ⇌ NH3

Complete questions 1-5 in the ICE box assignment

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Example: At 727°C the Keq for the dissociation of molecular iodine into iodine atoms is 3.80 ×10−5 I2(g) ⇌ 2 I(g) If the original concentration of molecular iodine is 0.200 M, calculate the concentration of atomic iodine at equilibrium. Keq =   [I2] [I] Initial Change Equilibrium

The Magnitude of the Keq Keq > 1 favours formation of products, equilibrium lies to the right ex. The decomposition of ozone: 2O3(g) ⇌ 3O2(g) At 298K the value of Keq is 2.0 x 1057. This means there is way more product than reactant. The equilibrium lies to the right and favors the products.

The Magnitude of the Keq Keq ≈ 1, there are measurable quantities of both reactants and products ex. The production of hydrogen gas: CO(g) + H2O(g) ⇌ CO2(g) + H2(g) At 700K the Keq is 5.09. Since the Keq is fairly close to 1, the concentrations of the reactants and products at equilibrium will be approximately equal (slightly higher concentration of products than reactants).

The Magnitude of the Keq Keq < 1, favours formation of reactants, equilibrium lies to the left (this means not a lot of reactants react) ex. The combination of nitrogen and oxygen: N2(g) + O2(g) ⇌ 2NO(g) At 298K the Keq is 1.0 x 10-25, which means the equilibrium lies to the left. This means at equilibrium, the concentration of the reactants is way higher than the products. This is good for us because if Keq was really high, oxygen would combine with nitrogen in the atmosphere, and we would not be able to breathe.

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