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Ch.14 - Chemical Kinetics
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232당신이 사용하는 게 아니라요?교과서 변경
14장, 문제 39a

(a) For the generic reaction A → B what quantity, when graphed versus time, will yield a straight line for a first-order reaction?

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1
Identify the order of the reaction given in the problem, which is a first-order reaction.
Recall that for a first-order reaction, the rate of reaction is directly proportional to the concentration of one reactant. The rate law can be expressed as: \(rate = k[A]\), where \(k\) is the rate constant and \([A]\) is the concentration of reactant A.
Understand that for a first-order reaction, the natural logarithm of the concentration of the reactant versus time will yield a straight line. This is derived from the integrated rate law for a first-order reaction: \(\ln[A] = -kt + \ln[A]_0\), where \([A]_0\) is the initial concentration of A.
Set up the graph with time (t) on the x-axis and the natural logarithm of the concentration of A (\(\ln[A]\)) on the y-axis.
Plot the data points for \(\ln[A]\) versus time and draw the best fit line. The slope of this line will be equal to \(-k\), and the y-intercept will be \(\ln[A]_0\).

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주요 개념

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First-Order Reactions

First-order reactions are chemical reactions where the rate is directly proportional to the concentration of one reactant. This means that as the concentration of the reactant decreases, the rate of reaction also decreases in a linear fashion. The mathematical representation of a first-order reaction is given by the equation: rate = k[A], where k is the rate constant and [A] is the concentration of reactant A.
추천 영상:
가이드 코스
02:29
First-Order Reactions

Integrated Rate Law

The integrated rate law for a first-order reaction relates the concentration of the reactant to time. It is expressed as ln[A] = -kt + ln[A]₀, where [A]₀ is the initial concentration, k is the rate constant, and t is time. When plotted, a graph of ln[A] versus time yields a straight line with a slope of -k, indicating that the reaction follows first-order kinetics.
추천 영상:
가이드 코스
01:52
Rate Law Fundamentals

Graphing Reaction Kinetics

Graphing is a crucial tool in analyzing reaction kinetics. For first-order reactions, plotting the natural logarithm of the concentration of the reactant (ln[A]) against time results in a straight line. This linear relationship allows chemists to determine the rate constant (k) and understand the reaction's behavior over time, providing insights into the reaction mechanism and dynamics.
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가이드 코스
03:06
Chemical Kinetics
관련 실천
교과서 질문

Consider the reaction of peroxydisulfate ion (S2O82-) with iodide ion (I-) in aqueous solution:

S2O82-(aq) + 3 I-(aq) → 2 SO42-(aq) + I3-(aq)

 At a particular temperature, the initial rate of disappearance of S2O82- varies with reactant concentrations in the following manner:

Experiment [S2O82-] (M) [I-] (M) Initial Rate (M/s)

1 0.018 0.036 2.6 × 10-6

2 0.027 0.036 3.9 × 10-6

3 0.036 0.054 7.8 × 10-6

4 0.050 0.072 1.4 × 10-5

(a) Determine the rate law for the reaction and state the units of the rate constant.

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교과서 질문

(a) The gas-phase decomposition of SO2Cl2, SO2Cl2(g) → SO2(g) + Cl2(g), is first order in SO2Cl2. At 600 K the half-life for this process is 2.3 × 105 s. What is the rate constant at this temperature?

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교과서 질문

Consider the gas-phase reaction between nitric oxide and bromine at 273°C: 2 NO(g) + Br2(g) → 2 NOBr(g). The following data for the initial rate of appearance of NOBr were obtained:

Experiment [NO] (M) [Br2] (M) Initial Rate (M/s)

1 0.10 0.20 24

2 0.25 0.20 150

3 0.10 0.50 60

4 0.35 0.50 735 

(b) Calculate the average value of the rate constant for the appearance of NOBr from the four data sets.

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교과서 질문

(b) How can you calculate the rate constant for a first-order reaction from the graph you made in part (a)?

교과서 질문

The decomposition of sodium bicarbonate (baking soda), NaHCO3(s), into Na2CO3(s), H2O(l), and CO2(g) at constant pressure requires the addition of 85 kJ of heat per two moles of NaHCO3. (b) Draw an enthalpy diagram for the reaction.

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