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Ch.14 - Chemical Kinetics
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 14th EditionCh.14 - Chemical KineticsProblema 51b
Capitolo 14, Problema 51b

(b) Does the rate constant for a reaction generally increase or decrease with an increase in reaction temperature?

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1
Understand the relationship between temperature and reaction rate: The rate of a chemical reaction typically depends on the temperature at which the reaction is carried out.
Recall the Arrhenius Equation: This equation, given by \( k = A e^{-\frac{E_a}{RT}} \), where \( k \) is the rate constant, \( A \) is the frequency factor, \( E_a \) is the activation energy, \( R \) is the gas constant, and \( T \) is the temperature in Kelvin, describes how the rate constant changes with temperature.
Analyze the effect of increasing temperature: Increasing the temperature \( T \) in the Arrhenius equation results in a decrease in the value of the exponent \( -\frac{E_a}{RT} \), making the entire exponent larger (less negative).
Examine the exponential term: As the exponent becomes larger, the value of \( e^{-\frac{E_a}{RT}} \) increases because the negative exponent becomes less negative.
Conclude the effect on rate constant: Since the exponential term increases with an increase in temperature, the rate constant \( k \) also increases.

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Rate Constant

The rate constant (k) is a proportionality factor in the rate equation of a chemical reaction, indicating the speed at which the reaction occurs. It is specific to a particular reaction at a given temperature and is influenced by factors such as temperature, concentration, and the presence of catalysts.
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Rate Constant Units

Arrhenius Equation

The Arrhenius equation describes how the rate constant of a reaction changes with temperature. It is expressed as k = A * e^(-Ea/RT), where A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the temperature in Kelvin. This equation shows that an increase in temperature generally leads to an increase in the rate constant.
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Arrhenius Equation

Activation Energy

Activation energy (Ea) is the minimum energy required for reactants to undergo a chemical reaction. Higher temperatures provide more kinetic energy to the molecules, increasing the likelihood that they will overcome the activation energy barrier, thus enhancing the reaction rate and increasing the rate constant.
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Activity Series Chart
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Sucrose 1C12H22O112, commonly known as table sugar, reacts in dilute acid solutions to form two simpler sugars, glucose and fructose, both of which have the formula C6H12O6. At 23 C and in 0.5 M HCl, the following data were obtained for the disappearance of sucrose: Time (min) 3C12H22o11 4 1M2 0 0.316 39 0.274 80 0.238 140 0.190 210 0.146 (a) Is the reaction first order or second order with respect to 3C12H22O114?

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