CHM102 MasteringChemistry Ch. 14
The rate constant for a certain reaction is k = 1.60 × 10−3 s−1 . If the initial reactant concentration was 0.450 M, what will the concentration be after 5.00 minutes?
0.278 M
What is the rate constant of a first-order reaction that takes 513 seconds for the reactant concentration to drop to half of its initial value?
1.35 x 10^-3 s-1
What is the half-life of a first-order reaction with a rate constant of 2.90 × 10−4 s−1?
2390 s
A certain first-order reaction has a rate constant of 7.40×10−3 s−1. How long will it take for the reactant concentration to drop to 18 of its initial value?
281 s
A zero-order reaction has a constant rate of 1.70×10−4 M/s. If after 80.0 seconds the concentration has dropped to 2.00×10−2 M, what was the initial concentration?
3.36 x 10^-2 M
Imagine that you took a road trip. Based on the information in the table, what was the average speed of your car? Time Mile marker 3:00pm 11 8:00pm 262
50.2 mph
The formation of nitrogen dioxide and oxygen, NO(g) + O3(g) ⇌ NO2(g) + O2(g) is first order in NO and first order in O3. If the concentration of NO was increased by half and the concentration of O3 was quadrupled, by what factor would the reaction rate increase?
6
Consider the following reaction and data: H2 + 2IF → 2HF + I2 Time I2 concentration 5 1.13 15 1.69 A) What is the average rate of formation of I2? B) Based on your answer to Part A, what is the average rate of formation of HF? C) Based on your answer to Part A or B, what is the average rate of change of H2? Remember that reactant concentrations decrease over time.
A) 0.056 M/s B) 0.112 M/s C) -0.056 M/s
reactants: 210 kJ products: 100 kJ A) What is the value of the activation energy of the uncatalyzed reaction? B) What is the value of the enthalpy change of the uncatalyzed reaction? C) What is the value of the activation energy of the uncatalyzed reaction in reverse? D) What is the value of the enthalpy change of the uncatalyzed reaction in reverse? E) How does the presence of a catalyst affect the activation energy of a reaction? F) How does the presence of a catalyst affect the enthalpy change of a reaction?
A) 175 kJ B) -125 kJ C) 300 kJ D) 125 kJ E) A catalyst decreases the activation energy of a reaction. F) A catalyst does not affect the enthalpy change of a reaction.
For the reaction A + B + C → D + E, the initial reaction rate was measured for various initial concentrations of reactants. The following data were collected: Trial [A] [B] [C] Initial rate 1 0.10 0.10 0.10 3 x 10^-5 2 0.10 0.10 0.30 9 x 10^-5 3 0.20 0.10 0.10 1.2 x 10^-4 4 0.20 0.20 0.10 1.2 x 10^-4 A) What is the reaction order with respect to A? B) What is the reaction order with respect to B? C) What is the reaction order with respect to C?
A) 2 B) 0 C) 1
A) Based on the reaction profile, how many intermediates are formed in the reaction A→D? B) How many transition states are there? C) What step is the fastest? D) Is the reaction A → D exothermic or endothermic?
A) 2 B) 3 C) C → D D) endothermic
Consider the reaction: 2H3PO4 → P2O5 + 3H2O A) Using the information in the following table, calculate the average rate of formation of P2O5 between 10.0 and 40.0 s. B) Determine the average rate of decomposition of H3PO4 between 10.0 and 40.0 s. Time (s) = [P2O5] (M) 0 0 10.0 3.00 x 10^-3 20.0 6.00 x 10^-3 30.0 7.80 x 10^-3 40.0 9.00 x 10^-3 50.0 9.60 x 10^-3
A) 2.00 x 10^-4 M/s B) 4.00 x 10^-4 M/s
Consider the following elementary steps that make up the mechanism of a certain reaction: 1) 2X → Y + Z 2) Y + 2L → M + Z A) What is the overall reaction? B) Which species is a reaction intermediate? C) What is the rate law for step 1 of this reaction? D) What is the rate law for step 2 of this reaction?
A) 2X + 2L → M + 2Z B) Y C) rate = k*[X]^2 D) rate = k*[Y]*[L]^2
The first-order rate constant for the decomposition of N2O5, 2N2O5(g) → 4NO2(g) + O2(g), at 70∘C is 6.82×10−3s−1. Suppose we start with 2.80×10−2 mol of N2O5(g) in a volume of 1.8 L . A) How many moles of N2O5 will remain after 5.0 min? B) How many minutes will it take for the quantity of N2O5 to drop to 1.5 × 10−2 mol? C) What is the half-life of N2O5 at 70∘C?
A) 3.6 x 10^-3 mol B) 1.5 min C) 102 s
Consider the reaction: 5Br−(aq) + BrO−3(aq) + 6H+(aq) → 3Br2(aq) + 3H2O(l) A) The average rate of consumption of Br− is 1.36×10−4 M/s over the first two minutes. What is the average rate of formation of Br2 during the same time interval? B) What is the average rate of consumption of H+ during the same time interval?
A) 8.16 x 10^-5 M/s B) 1.63 x 10^-4 M/s
The following diagram represents an imaginary two-step mechanism. Let the red spheres represent element A, the green ones element B, and the blue ones element C. A) Write the equation for the net reaction that is occurring. B) Identify the intermediate. C) Identify the catalyst
A) AB + AC → BA2 + C B) A C) A2
Consider the reaction A + 2B ⇌ C whose rate at 25 ∘C was measured using three different sets of initial concentrations as listed in the following table: Trial [A] [B] Initial rate 1 0.30 0.030 3.2 x 10^-3 2 0.30 0.060 6.5 x 10^-3 3 0.60 0.030 1.3 x 10^-2 A) What is the rate law for this reaction? B) Calculate the initial rate for the formation of C at 25 degrees C, if [A]=0.50M and [B]=0.075M.
A) rate = k[A]^2[B] B) 2.3 x 10^-2 M/s
What chemical equation is consistent with this data?
B→2A
How does the instantaneous rate of reaction change as the reaction proceeds?
It decreases
Platinum is used to catalyze the hydrogenation of ethylene: H2(g) + CH2CH2(g)− → CH3CH3(g) Chlorofluorocarbons (CFCs) catalyze the conversion of ozone (O3) to oxygen gas (O2): 2O3(g)− → 3O2(g) Magnesium catalyzes the disproportionation of hydrogen peroxide to produce water and oxygen: 2H2O2(aq)− → 2H2O(l) + O2(g) What type of catalysts are platinum, CFCs, and magnesium under these conditions?
homogeneous catalyst: CFCs heterogeneous catalysts: platinium and magnesium
Consider the formation of nitrogen dioxide and oxygen: NO(g) + O3(g) ⇌ NO2(g) + O2(g) The reaction is first order in O3 and second order overall. What is the rate law?
rate = k[NO][O3]
