Questions tagged [rate-equation]
The rate-equation tag has no usage guidance.
29
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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 ...
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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 ...
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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
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Modelling barrier-less reactions
I am currently exploring a few dissociative reactions whose PES is barrierless (no first order saddle point). I have found a few approaches in literature like flexible nudged elastic band theory, ...
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The Mechanism of Termolecular Reactions
How does a termolecular elementary reaction happen under the law of mass action? My physical chemistry textbook only says details about bimolecular and unimolecular reactions with collision theory. I ...
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Steady state approximation for three-step cycle
How to write the steady state for $\ce{A}?$
$$\ce{A ->[$k_1$] B ->[$k_2$] C ->[$k_3$] A}$$
Species $\ce{A}$ seems to appear on both side of equation as it uses itself to produce some of ...
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Which reaction to consider for overall rate
So I have a multistep reaction
\begin{align}
\ce{4 NH3 + 5 O2 &-> 4 NO + 6 H2O}\\
\ce{2 NO + O2 &-> 2 NO2}\\
\ce{3 NO2 + H2O &-> 2 HNO3 + NO}
\end{align}
If I know the initial ...
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Lindemann-HInshelwood mechanism difference between high and low concentration
I have a gas reaction which follows the Lindemann-Hinshelwood mechanism and want to calculate the rate constant at low and at high concentrations of the gas but I find myself stuck at what my next ...
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Effect of stirring and shaking on chemical kinetics
Why don't we take the effects of stirring and shaking on the rates of chemical reactions? While studying chemical kinetics, I've seen that the rates depend on the concentrations of various species, ...
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Why isn't the rate of an elementary reaction expressed in activity?
Why don't chemists use $r_\ce{X}=\frac{\text{d}a_\ce{X}}{\text{d}t}$ where $a_\ce{X}$ is the chemical activity of species $\ce{X}$ and corresponding rate law for elementary reactions as $r=ka_1^{\...
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Is my derivation for the reaction orders of a single-step reaction valid?
Recently in my chemistry class I learned about reaction orders. For some reaction $\ce{r_1A1}+\ce{r_2A2}+\dots+\ce{r_nA_n}\rightarrow\ce{B}$, $m_1,\dots{,m_n}$ are the orders of that reaction. The ...
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Rate of SN1 reaction in derivative of furan and thiopene
When I was practising questions on the rate of SN1 mechanisms, I stumbled across this:
I could eliminate options B and D because they can stabilize by only cross conjugation (if I am correct) and ...
- 111
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What equation can be used to determine the mass of water evaporation over time, when cooking?
When baking, cooking or writing recipes, it would be useful to have a ballpark estimate of evaporation rates. This question asks about water, although the answer would ideally include an ...
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Can the overall order of a reaction ever be strictly less than $1$?
In A-level chemistry we are taught that:
To every reaction: $$\sum_{i=1}^n c_iA_i\to\sum_{j=1}^m d_jB_j$$There is a rate equation: $$r=\kappa[A_1]^{\alpha_1}[A_2]^{\alpha_2}\cdots[A_n]^{\alpha_n}$$...
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Determining reaction order from absorbance
A reaction is initiated in a solution which contained a dissolved component. The transmittance was measured at $\pu{240 nm}$ in a $\pu{2.54 cm}$ long cell. At $t = 0$ the transmittance was $1$. $\...
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