CHEM 0N01 Chapter Notes - Chapter 6: Reaction Rate, Reaction Mechanism, Rate-Determining Step

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24 May 2016

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How does a reaction proceed (reaction mechanism) How fast a reaction takes (reaction rate) Is the change in concentration of a reactant or product with time. [r] = change in [reactants] over a period of time. [p] = change in [products] over a period of time. *because [r] decreases with time, [r] is negative. Rate for a specific instance in time (tangent line) The average rate of decomposition of ammonia is 4. 5x10-2 (mol/l/s) 4nh3 + 5o2 4no + 6h2o: rate of h2o production, rate of no production, rate of o2 combustion: Methods for measuring rates: measuring the volume of gas produced reactants products (g) Omar kanny: measuring change in color intensity. Spectrometer or colorimeter can measure changes in light intensity. Used when one of the reacts or products is coloured: measuring change in acidity. Use a ph meter to measure changes hydrogen ion concentration: measuring change in electrical conductivity. Used when there are ions consumed/produced: measuring changes in pressure.

Related Questions

What is the instantaneous rate of the reaction at t=800s?

The answer is rate= 6.8x10^-5 m/s but I need an explanation as to how to do the problem

A student studies the kinetics of reaction 1 below using a clock reaction technique, reaction 2, and the procedures given in this experiment. For reaction mixture 1, he measures a time to color change of 121 seconds and for reaction mixture 2, he measures a time of 58 seconds. The temperatures of the reaction mixtures were the same for both experiments.

6Iâ (aq)+ BrO3â (aq) + 6H+(aq) --> 3I2 (aq) + Brâ (aq) + 3H2O(l) (Reaction1,slow)

I2 (aq) + 2 S2O32â (aq) --> 2 Iâ (aq) + S4O62â (aq) (Reaction 2, fast)

a. Determine the change in concentration of S2O32â that occurred during the time period measured. This should be the same for both the reaction mixtures. First, use M1V1=M2V2 to determine the initial concentration of the S2O32â after mixing the contents of the two flasks but before the reaction begins. Next, find the final concentration of S2O32â by remembering that all the S2O32â is consumed when the color change occurs. You can then find the change in the concentration of S2O32â.

[S2O32â]0 =

â[S2O32â] =

b. Use the stoichiometry of Reactions 1 and 2 to determine the change in concentration of BrO3â during

the same time period. â[BrO3â] =

c. Calculate the initial rate for each reaction mixture. Recall that Rate = â â[BrOâ ] / ât

Rate for mixture 1:

Rate for mixture 2:

d. Method of Initial Rates

Complete the table below using M1V1=M2V2 to find the initial concentration of each reactant after mixing the contents of flasks I and II for both reaction mixtures. Enter the initial rates computed above.

Rxn Mixture [Iâ]0(M) [BrO3â]0(M) [H+]0 (M) Rate (M/s)

Use the method of initial rates and the relevant data above to determine the order of reaction 1 with respect to the concentration of iodide ions.

Order with respect to [Iâ]:_________________________

e. It is critical for the success of this experiment that the concentrations of the reactants Iâ, BrO3â, and H+ do not change significantly over the time period measured.

Why is this important?

f. By what percent did the bromate ion concentration change during the time period considered for mixture 1 in this experiment?

PercentChange = (|â[BrO3â ]| / [BrO3â ]0 ) x 100%

The following set of data was obtained by the method of initial rates for the reaction: 2 HgCl_2 (aq) + C_2O_4^2-(aq) rightarrow 2 Cl^- (aq) + 2CO_2(g) + Hg_2Cl_2(s) What is the value of the rate constant, k? A) 1.4 times 10^-5 1/M^2 s B) 1.3 times 10^-7 1/M^2 s C) 1.4 times 10^-8 1/M^2 s D) 1.3 times 10^-4 1/M^2 s The rate constant, k, for a first-order reaction is equal to 4.2 times 10^-4 s^-1. What is the half-life for the A) 1.7 times 10^3 s B) 1.2 times 10^3 s C) 2.4 times 10^3 s D) 2.9 times 10^-4 s The first order decomposition of hydrogen peroxide occurs according to the equation 2H_2O_2(aq) - 2 H_2O(l) + O_2(g) The first-order decomposition of hydrogen peroxide occurs according to the equation 2 H_2O_2(aq) - 2 H_2O(l) + O_2(g) Using data from a measurement of the concentration of the reactant at different during the progress of the reaction, which plot will produce a straight line? A) 1/[H_2O_2] versus time B) [H_2O_2] versus time C) [H_2O_2]^2 versus time D) ln[H_2O_2]versus time For the reaction shown below, which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product? C(s) + 2 H_2(g) = CH_4(g) Delta H degree = - 74.8 kj A) increasing the volume B) raising the temperature C) lowering the temperature D) adding more C For the reaction shown below, what is the relationship between the rate of formation of Br_2 and the rate of reaction of Br^- over the same time period? ClO_2^- (q) + 4 Br^- (aq) + 4 H^+ (aq) - Cl^- (aq) + 2 Br_2(aq) + 2 H_2 O(l) A) rate of formation of Br_2 = 2 = rate of reaction of Br^- B) rate of formation of Br_2 = 1/4 = rate of reaction of Br^- C) rate of formation of Br_2 = 2 =rate of reaction of Br^- D) rate of formation of Br_2 = 1/2 = rate of reaction of Br^- The decomposition of ammonia is 2 NH_3(g) = N_2(g) + 3 H_2(g). If K_p is 1.5 times 10^3 at 400 degree C, what is the partial pressure of ammonia at equilibrium when N_2 is 0.10 atm and H_2 is 0.15 atm? A) 4.4 times 10^6 atm B) 2.1 times 10^3 atm C) 4.7 times 10^-4 atm D) 2.2 times 10^-7 atm

CHEM 0N01 Chapter Notes - Chapter 6: Reaction Rate, Reaction Mechanism, Rate-Determining Step

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