Questions tagged [rate-equation]

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22 views

For an a plot of lnk against 1/T from Arrhenius equation, why does the y-intercept change when Ea changes?

According to Arrhenius equation, k = Ae^(-Ea/RT). Thus graph of lnk against 1/T is a straight line with negative gradient and positive y intercept. To plot a graph for lower activation energy, the ...
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1answer
36 views

Calculate concentration of product after time passed

If I have two parallel reactions: A --> P$1$ (k$_1$ = $0.00010$ s$^{-1}$) A --> P$2$ (k$_2$ = $0.00050$ s$^{-1}$) and know that the initial concentration of A is $0.0417$ M. How can I ...
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25 views

Calculating the concentration of reactants and products in parallel reactions after a time t

A substance A reacts with a solvent B to form an intermediate product IP. The reaction is bimolecular. The conc. of the solvent is constant at $12$M. IP can then react to form the two products P$1$ ...
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0answers
52 views

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 $1$. $\...
-2
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0answers
19 views

Why is a pseudo first order reaction also called pseudounimolecular reaction?

Molecularity is defined as the number of reacting species taking part in an elementary reaction . So for example if we take ester hydrolysis then as the concentration of acid/ alkali does not get ...
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32 views

Determining ion charge using rate constants and ionic strength

I am given the following data: The rate constant $k$ at $\pu{25 ^\circ C}$ in a reaction of persulfate ions and iodide ions in a water solution is assumed to vary with the total ionic strength of the ...
8
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4answers
193 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}...
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33 views

Are catalyst concentrations included in the rate expression?

I have seen different rate expressions, some which include the concentration of the catalyst as a term in the rate expression, and others that do not. I thought the rate expression only includes terms ...
5
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2answers
82 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.: ...
0
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1answer
23 views

How is the equilibrium expression (law of mass action) related to the rate law? [duplicate]

Every chemistry textbook I've read will have a chapter on the rate law. It will say something like, given a reaction $a\text{A} + b\text{B} \rightarrow c\text{C} + d\text{D}$, the rate law (for the ...
2
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1answer
50 views

Finding the rate of a reaction given experimental data for reaction kinetics [closed]

Here is the question: For the reaction: $$\ce{2 A + 2 B → C + D}$$ The following data was obtained from three experiments: \begin{array}{c|ccc}\hline \bf{Experiment} &\textbf{[A] (mol/L)} &\...
5
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2answers
94 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} &...
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0answers
54 views

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 ...
4
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1answer
168 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 &<=>[$k_2$]...
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1answer
206 views

Does mass affect rate of reaction?

Suppose I am reacting HCl with CuCO3. Experiment 1: I use 2g powdered CuCO3 Experiment 2: I use 4g powdered CuCO3 All other variables are kept constant. Will this have any affect on rate of reaction? ...
4
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2answers
99 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....
3
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1answer
73 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)...
3
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1answer
111 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 ...
2
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36 views

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 ...
4
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52 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 ...
2
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0answers
115 views

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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0answers
48 views

Using the steady state approximation in the decomposition of nitramide to determine rate law

$\ce{O2NNH2 (aq) ->[\mathit{k}_1] O2NNH- (aq) + H+ (aq)}$ $\ce{O2NNH- (aq) + H+ (aq) ->[\mathit{k}_{-1}] O2NNH2 (aq)}$ $\ce{O2NNH- (aq) ->[\mathit{k}_2] N2O(g) + OH- (aq)}$ $\ce{H+ (aq) + OH-...
2
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1answer
65 views

Are the orders of reactants with respect to a reaction different for different starting concentrations?

If the reaction is repeated with $\pu{2 M}$ ethyl iodide the pyridine concentration decreases as shown below. Give the rate law of the reaction in terms of pyridine and ethyl iodide. Explain your ...