Reaction rates and rate law expressions Page 1

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1 Reaction rates and rate law expressions Page 1 1 What does a large Keq (greater than 1) indicate? more products than reactants at equilibrium more reactants than products at equilibrium the reaction stops when it reaches equilibrium the reaction reaches equilibrium quickly 2 What does the equilibrium constant (Keq) express? the ratio of products to reactants at equilibrium the amount of products present at equilibrium how fast the reaction reaches equilibrium 3 Given the rate-law expression; rate = k []2[]1 ; tripling the concentration of "" would... make the reaction three times as fast make the reaction slow down by a factor of 2 make the reaction increase by a factor of 2 make the reaction increase by a factor of 4 make the reaction increase by a factor of 9 4 utting firewood into kindling (smaller pieces) increases the rate of the exothermic combustion reaction by increasing the amount of fuel increasing the amount of oxygen available. reducing the amount of oxygen available changing the reaction into an endothermic process 5 Given the rate-law expression; rate = k []1[]3 ; the over all order of the reaction would be... 1st order 2nd order 3rd order 4th order I'll have fries with that order 6 t equilibrium, the forward rate slows down the backwards reaction stops forwards and backwards happen at the same rate the forwards and backwards reactions happen slowly

2 Reaction rates and rate law expressions Page 2 7 Given the rate-law expression; rate = k [Y]2[M]1 ; the order with respect to "Y" is... 2nd order (and 3rd order overall) 1st order and 2nd order with respect to M 3rd order with respect to both 2nd order ( and 1st order over all) 8 What does a small Keq indicate? the reaction is very slow a lot of energy is needed to get the reaction started more reactants than products at equilibrium more products than reactants at equilibrium 9 collision requires to be effective only enough energy favorable orientation enough energy and favorable orientation a reaction mechanism 10 Hydrogen iodide decomposes as: 2HI --> H2 + I2 the average reaction rate = -1[HI]/2 t the negative sign used in the rate expression indicates that: There are repulsive forces between the reactants The concentration of HI decreases with time The concentration of the reactants is less than that of the products The reaction rate is decreasing with time 11 The concentration of chemical is 0.22 M at the beginning; after 4 seconds the concentration is.1 M. alculate the average reaction rate.22 M/s -.22M/s -.12 M/s -.03 M/s -.10 M/s 12 If we add SO2(g) to the equation 2 SO2(g) + O2(g) <-- --> 2 SO3(g) + heat quilibrium would shift towards the products quilibrium would shift towards the reactants oncentration of O2 would increase oncentration of SO3 would decrease

3 Reaction rates and rate law expressions Page 3 13 If we add heat to the equation 2 SO2(g) + O2(g) <-- --> 2 SO3(g) + heat concentration of reactants would increase concentration of products would increase concentration of neither would increase concentration of both would increase 14 If we add reactants to a system at equilibrium, the system shifts towards reactants the system shifts towards products nothing will happen, you are at equilibrium the rate of the reverse reaction will increase 15 when calculating rate law expressions the square brackets mean... multiply raise to the power of concentration they got tired of using round brackets 16 If we add SO3(g) to the equation 2 SO2(g) + O2(g) <-- --> 2 SO3(g) + heat which concentrations would increase? SO3 SO3 and O2 SO2 and O2 SO3, O2 and SO2 17 Given the rate-law expression; rate = 7.5 M-2min-1 []2[]1 ; if =.3M, and =.2 M rate = M/min rate = M/min rate = M/min rate = 7.5 M/min 18 Given: rate = M-3 s-1 [N2]3[H2]1 when the concentration of nitrogen is increased from.1m to.3m, the rate should increase by a factor of 3 decrease by a factor of 3 increase by a factor of 6 decrease by a factor of 6 increase by a factor of 27

4 Reaction rates and rate law expressions Page 4 19 if the concentration of ammonia (NH3) is lowered from.5m to.1 M in a typical reaction we would expect the reaction rate to increase by.4 M decrease by.4 M increase by some amount decrease by some amount either decrease or remain the same 20 When copper was added to the iodine clock reaction, it was found that the reaction rate decreased. This means that copper is: a catalyst because reaction time increased a catalyst because the u remained unchanged an inhibitor because reaction time increased an inhibitor because the u remained unchanged 21 This rate equation: Rate=6[]0[]1[]2 is of the order: What would be the rate for this reaction: Rate=6[]0[]1[]2 if [] = 10M, [] = 2M, [] = 2M 0 M/min 6 M/min 24 M/min 48 M/min 23 What does (46)(42)=? an we take a break and review exponents?

5 Reaction rates and rate law expressions Page 5 24 What does (46)/(42)=? Let's stop and talk about dividing exponents catalyst is... a substance used up in a chemical reaction one of the products of a chemical reaction makes a chemical reaction go slower but is not a reactant or a product something that increases the rate of a reaction by allowing transition complexes with lower energies always very expensive 27 Given 2Fel2 + Snl2 --> 2Fel2 + Snl4 and the rate-law; rate = k [Fel2]2[Snl2]1 The order of this reaction is 1 The order of this reaction is 2 The order of this reaction is 3 The order of this reaction is 4 This reaction is "out of order" 28 Which of the following statements about a catalyst is true? catalyst can initiate a reaction catalyst can be changed during a reaction catalyst can be consumed during a reaction catalyst can accelerate a reaction 29 Given the rate-law expression; rate = k []o[]2 ; tripling the concentration of "" would... triple the rate increase the rate by a factor of 9 decrease the rate by a factor of 9 have no effect on the rate stop the reaction completely

6 Reaction rates and rate law expressions Page 6 30 Which reactant has the most POWR in this reaction: Rate=6[]0[]1[]2 They're all equal 31 t equilibrium, we have more products than reactants We have more reactants than products We can measure to determine the concentration of products and reactants

7 Reaction rates and rate law expressions Page 7 nswer Key : Reaction rates and rate law expressions Question: nswer