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Based on CaCO 3 (s) CaO(s) + CO 2 (g), which

Based on CaCO 3 (s) CaO(s) + CO 2 (g), which of the following can attain equilibrium? Start with. (K p = P CO2 ). (a) ...pure CaCO 3. “YEP.” . (it breaks down, forming products until the amt. of CO 2 is “right”) . (b) ...CaO and some CO 2 at P > K p. “YEP.”.

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Based on CaCO 3 (s) CaO(s) + CO 2 (g), which

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  1. Based on CaCO3(s) CaO(s) + CO2(g), which of the following can attain equilibrium? Start with... (Kp = PCO2) (a) ...pure CaCO3 “YEP.” (it breaks down, forming products until the amt. of CO2 is “right”) (b) ...CaO and some CO2 at P > Kp “YEP.” (too much CO2; it reacts w/available CaO until amt. of CO2 is “right”) “NOPE.” (c) ...CaCO3 and some CO2 at P > Kp (too much CO2, but no CaO for it to react with in order to attain the “right” amt. of CO2) (d) ...CaCO3 and CaO “YEP.”

  2. The Magnitude of the Equilibrium Constant If K >> 1... products are favored. Eq. “lies to the right.” If K << 1... reactants are favored. Eq. “lies to the left.” The K for the forward and reverse reactions are NOT the same. -- they are reciprocals -- You must write out the equation and specify the temperature when reporting a K.

  3. Find Kc @ 472oC for N2(g) + 3 H2(g) 2 NH3(g) At equilibruim @ 472oC…[NH3] = 0.00272 M [N2] = 0.0402 M [H2] = 0.1207 M. Calculating Equilibrium Constants (1) If the concentrations of all substances at equilibrium are known, plug and chug. = 0.105

  4. (2) If you know the concentrations of only some substances at equilibrium, make a chart and use reaction stoichiometry to figure out the other concentrations at equilibrium. THEN plug and chug. “Mr. B, what kind of chart?” “Ice, ice, baby…” I = “initial” C = “change” E = “equilibrium”

  5. Put “at eq.” #s into Kc expression… At 1000 K, the amounts shown below are known. Find Kc @ 1000 K. 2 SO3(g) 2 SO2(g) + O2(g) initial 6.09 x 10–3 M 0 M 0 M D–3.65 x 10–3 M +3.65 x 10–3 M +1.825 x 10–3 M at eq. 2.44 x 10–3 M +3.65 x 10–3 M +1.825 x 10–3 M = 4.08 x 10–3

  6. rxn. proceeds rxn. proceeds By knowing K, we can... (1) predict the direction of a reaction (2) calc. amts. of R and P once eq. has been reached, if we know init. amts. of everything reaction quotient, Q: what you get when you plug the R and P amts. at any given time into the eq.-constant expression If Q > K... (Be sure you know WHY.) If Q < K... If Q = K... we are at eq.

  7. For H2(g) + I2(g) 2 HI(g), Kc = 51 at a temp. of 488oC. If you start with 0.020 mol HI, 0.010 mol H2, and 0.030 mol I2 in a 2.0-L container, which way will the reaction proceed? HI! rxn. proceeds to eq. (need more product) = 1.3 < 51 From an MSDS for HI(aq)… (i.e., hydroiodic acid) “May cause congenital malformation in the fetus. Corrosive - causes burns. Harmful if swallowed, inhaled, or in contact with skin. Very destructive of mucous membranes. May affect functioning of thyroid. May increase size of skull.”

  8. For PCl5(g) PCl3(g) + Cl2(g), Kp = 0.497 at 500 K. At equilibrium, the partial pressures of PCl5 and PCl3 are 0.860 atm and 0.350 atm, respectively. Find the partial pressure of Cl2. 1.22 atm (Did this rxn start with only PCl5?)

  9. For the reaction in the previous problem, if a gas cylin- der at 500 K is charged with PCl5 at 1.66 atm, find the partial pressures of all three substances at equilibrium. PCl5(g) PCl3(g) + Cl2(g) initial 1.66 atm 0 atm 0 atm D–x x x at eq. 1.66 – xx x x = 0.693 atm or –1.190 atm a c b

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