Questions tagged [rate-equation]
The rate-equation tag has no usage guidance.
74
questions
10
votes
1
answer
293
views
Are there any genuine, elementary ternary reactions?
Macroscopically, reaction rates can be of varied order. But mechanistically, most reactions are first-order or second-order/binary (e.g. SN2, many catalyst surface reactions, dimers). Most processes ...
- 261
8
votes
4
answers
833
views
Deriving kinetic equations for reversible reactions
Problem
Given the reaction $\ce{A <=>[$k_\mathrm f$][$k_\mathrm b$] B}$ with rate constants $k_\mathrm f = \pu{4E-2 s-1}$ and $k_\mathrm b = \pu{10^{-2} s-1}$. Initially, $\pu{2 mol}$ of $\ce{A}...
- 1,817
8
votes
1
answer
23k
views
What does a fractional order of reaction mean for the mechanism?
I'm doing a high school/sixth form college investigation of the kinetics between magnesium ribbon and hydrochloric acid. I have obtained a rate order was $1.5$ with reference to $[\ce{H+}]$ and hence ...
- 81
6
votes
2
answers
799
views
Why do alkenes (olefins) burn hotter than alkanes (paraffins), even though alkanes are denser and more hydrogen-rich?
Burning hydrogen releases more total energy than combusting carbon, and all alkanes are denser as well, so why are flame temperatures for alkene molecules higher than their equivalent alkanes?
P.S.: ...
- 1,795
5
votes
2
answers
5k
views
Determine vmax and enzyme concentration (Michaelis–Menten)
I am given that the enzyme concentration is $\pu{15 nM}$ and the following data:
$$
\begin{array}{rl}
\hline
S/\pu{mM} & V/\pu{mM s^{-1}} \\
\hline
1 & 0.202 \\
2 & 0.368 \\
5 & 0....
- 1,095
5
votes
2
answers
198
views
Steady-state approach - how to find rate equation for intermediate?
The reaction mechanism for the formation of $\ce{NO2}$ is:
\begin{align}
\ce{NO + NO &<=>[$k_1$][$k_1'$] N2O2} & &\text{ (slow)} \\[0.2cm]
\ce{N2O2 + O2 &->[$k_2$] NO2 +NO2} &...
- 71
4
votes
1
answer
193
views
Can anyone explain, why there are coefficients 2 in the equation for rate of change [A]?
The reaction mechanism for the decomposition of $\ce{A2}$ is thought to be:
\begin{align}
\ce{A2 &<=>[$k_1$][$k_1'$] A + A} & &\text{ (fast)} \\[0.2cm]
\ce{A + B &<=>[$k_2$]...
- 49
4
votes
0
answers
563
views
Lindemann–Hinshelwood mechanism for a gas reaction
The effective rate constant for a gaseous reaction which proceeds by a Lindemann–Hinshelwood mechanism is $\pu{1.01E-5 s^-1}$ at a concentration of $\pu{4.6E-6 M}$ and $\pu{2.21E-5 s^-1}$ at a ...
- 1,095
3
votes
2
answers
370
views
Does 'k' in the rate law change with a change in volume
I'm a high school AP Chem student and we recently learned about the rate law and the Arrhenius equation. In school, we learned that rate constant 'k' is only changed with temperature or catalyst. ...
- 103
3
votes
1
answer
446
views
Concentration of products in tank reactor
I want to calculate the concentrations of all components in the outlet stream of the reaction: C$_2$H$_6$ -> C$_2$H$_4$ + H$_2$ (A -> B + C)
I have a tank reactor (isothermic and isobar): V= $...
- 1,095
3
votes
1
answer
279
views
Calculate the concentration of the reactant from the absorbance of the product without molar absorptivity
Given the reaction $\ce{A->B}$, where the absorbance of the product $\ce{B}$ has been measured (see the table below), and the initial concentration of $\ce{A}$ is $\pu{10^{-4} M},$ calculate the ...
- 1,095
3
votes
1
answer
164
views
First or second order reaction
I have that $100$ mM of K$_3$Fe(CN)$_6$ is dissolved in equimolar of the organic ion (which I assume is HCN). In the solution Fe(CN)$_6$$^{3-}$ reacts to form Fe(CN)$_6$$^{4-}$.
The formation of Fe(CN)...
- 1,095
3
votes
1
answer
312
views
Can the RDS be different in different direction in a multi-step reversible reaction?
The following mechanism is given in Peter Sykes when they are "talking about de-esterification" of an ester where the alcohol part is bulky-
Here the second step is given as RDS. According ...
- 363
3
votes
0
answers
61
views
Does real-world gas phase chemistry use "concentration reaction quotients" (K_c)?
As a theoretical chemist, my entire exposure to reaction quotients and equilibrium constants ($Q$ and $K$) is through thermodynamics ($\Delta G^\ominus = - RT \ln K_{eq}$ and so on).
So as I started ...
- 151
3
votes
0
answers
130
views
What is the physical significance of the frequency factor in the Arrhenius equation?
As the title says, I am wondering what the physical significance of the frequency/pre-exponential factor in the Arrhenius equation. My idea of it is that:
If the units of $E_a$ are energy per molecule,...
- 31