Questions tagged [reaction-order]

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Why is the reduction of iron oxide to iron considered a first order reaction where the chemical reactions hints at a second order reaction?

The general reduction of iron oxides is the following according to (Whiston et. al., 2021): $$ \ce{FeO + CO -> Fe + CO_2} $$ The rate law would then convert to: $$ \frac{d[\ce{Fe}]}{dt} = \frac{d[\...
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2 answers
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How to rationalize independence of half-life time from the initial concentration for the first order reaction?

Using the rate expression for the first order kinetics and expressing the half-life time, it can be proven the half-life time $t_\frac 1 2$ of the first order reaction is independent of its initial ...
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1 answer
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Does E1 mechanism always imply first order reaction?

Oxford University Press, Okuyama & Maskill: Organic Chemistry — Chapter 13: Multiple Choice Questions, Question 1: Which of the following statements regarding the E1 mechanism is wrong? a) ...
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Confusion regarding order of reaction

The following points are given in my textbook about order and molecularity:- (i) Order of a reaction is an experimental quantity. It can be zero and even a fraction but molecularity cannot be zero or ...
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1 answer
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Calculate rate constant of second order reaction and pseudo first order reaction

The reaction A + B -> Prod follows the second order kinetics. In an experiment, you initially have ten times as much B as A. The concentration of A varies with time according to the following data: ...
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Calculating ionic strength at different concentrations

Zn$^{2+}$ reacts with a molecule, B, in a solution at several different concentrations of NaCl. Determine the charge of the biomolecule and k$_0$ (second order) ​​(assume that Zn$^{2+}$ does not ...
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1 answer
234 views

Why is it that first order reactions never end? [duplicate]

I'm studying chemical kinetics in high school. We are studying Integrated Rate Equation of first order reactions - their derivations and graphs. Our teacher showed us a graph of: Concentration of ...
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2 votes
1 answer
56 views

Determine reaction order of Cyclopentadiene

Reaction: $\ce{2 C5H6 -> C10H12}$ For this reaction it is stated that $\pu{0.609 M}$ cyclopentadiene was formed in an ethanol solution. When the solution was heated $(\pu{40 ^\circ C})$ and ...
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Can two 1st order reactants in an overall 2nd order reaction have different rates?

I've recently done a saponification reaction of ethyl acetate with sodium hydroxide and used the initial rates method to find the order of reaction. (I change the concentration of one reactant and ...
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-3 votes
1 answer
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(Beginner Question) Reaction Word Problems [closed]

I am having trouble understanding how to create equations which can then be balanced. For example, if I am told that a freshly scraped piece of aluminum reacts with oxygen from the air to form a ...
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-1 votes
1 answer
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What are some three+ stage cyclical reactions that only go one direction?

I was imagining the origins of life and supposed that "humans are just a bunch of cyclical chemical reactions in a coat." Which made me wonder, what sort of cyclical chemical reactions ...
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Finding the reaction order from a given plot of chemical kinetics

What will be the order of the reaction for a chemical change having $\log t_{1/2}$ VS $\log a$ Where $a=$ Initial concentration of reactant and $t_{1/2} =$ Half Life? 0 order 1st order 2nd order None ...
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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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Surface-water hydrolysis reaction & reaction/adsorption kinetics model

I didn't major in Chem or Chem Eng when I was an undergraduate, so I have a rather limited background in this field, please forgive me if my questions are too basic or very wrong. I wish to model a ...
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Are there any pathways that can change a solution to all colors of the rainbow?

The challenge's like this. Suppose you have a beaker containing a liquid of transparent or any color. You add some drops of another liquid and the beaker turns into, say, red after some swishing. You ...
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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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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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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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2 votes
0 answers
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Plotting second order reaction with different reactants

In a laser flash photolysis experiment, $\ce{C6H5NH2}$ $(C_0 = \pu{60 \mu M})$ is oxidize to its corresponding radical cations. There are three possible reaction pathways for the formation of the ...
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How do the terms in a rate law relate to effectiveness and number of collisions of reactants?

In chemical kinetics, we use rate law to find the instantaneous rate of reaction. Let us consider a simple reaction $$\ce{aA + bB -> products}$$ where the rate law is $$\mathrm{rate} = k[\ce{A}]^a[\...
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How to graph a second order reaction with two different reactants

In a laser flash photolysis experiment, $\ce{C6H5NH2}$ $(C_0 = \pu{60 \mu M})$ is oxidized to the corresponding radical cation. The disappearance of radical cation is monitored spectrophotometrically ...
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3 votes
1 answer
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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)...
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3 votes
2 answers
517 views

Is the rate of a zero order reaction always independent of the concentration of its reactants?

Consider the following reaction : $\ce{A + B}$ $\rightarrow$ $\ce{Products}$ where order of the reaction w.r.t. $\ce{A}$ is $-1$ and order of the reaction w.r.t. $\ce{B}$ is $+1$. So, overall order of ...
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4 votes
1 answer
311 views

Determine reaction order and reaction rate

In a solution of $\ce{Fe^3+}$ the concentration was measured to be: $$\begin{array}{c|c} t/\pu{min} & \ce{[Fe^3+]}/\pu{\mu M} \\ \hline 10\ & 238\\ 20 & 227\\ 40\ & 206\\ 60\ & ...
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  • 427
2 votes
1 answer
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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 ...
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5 votes
4 answers
2k views

Formula for rate constant for the first order reaction

My lecturer mentioned that the formula for the rate constant $k$ for the first order reaction is $$k = \frac{2.0303}{t_{1/2}}\,\log\frac{[\ce{A}]_0}{[\ce{A}]_{t_{1/2}} - [\ce{A}]_0},\tag{1}$$ where $...
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In reaction equations, why are j and k sometimes capitalized to J and K?

From 'Leighton relationship' on Wikipedia: through the following mechanism:[2] ($J_1$) $$\ce{NO2 + h\nu (\lambda < 420 nm) → NO + O (^3P)}$$ ($k_2$) $$\ce{O (^3P) + O2 + M → O3 + M}$$ ($k_3$) $$\ce{...
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1 vote
1 answer
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Arrange in the order of their reactivity of SN2 reaction

Here in case of (1) it is more favorable towards SN1 reaction as it will create benzyl carbocation which is very stable. (2) Here it is more favorable towards SN1 as it is first of all allyl ...
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4 votes
1 answer
219 views

Relationship between molecularity and the reaction order

Should the molecularity be equal or less than the reaction order? Consider the reaction: $$\ce{H2(g) + I2(g) → 2 HI(g)}$$ If we consider the mechanism of this multi-step reaction, the molecularity is ...
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Is order defined for a reaction which does not follow power law dependence?

As per my knowledge , order of a reaction is the sum of exponents of all the terms in rate law of the reaction But reaction which do not follow power law dependence , for example , formation of HBr , ...
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Parallel reactions for one product

For me it is clear how I could solved the kinetic of a parallel reaction like this But, how can I solve if this would be the case: Thanks in advance!
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Is this statement valid for reactions of all orders? [duplicate]

My textbook (not an international standard) states that for the first order reactions only The quantity of reactant remaining after $n$ half lives is $$A_n = \frac{A_0}{2^n},$$ where $A_0$ is the ...
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2 answers
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Inconsistency in Elementary Bi-Molecular Reaction Rate Expressions

Assume the following bi-molecular reaction is elementary as written with rate constant $k_\mathrm{f}$: $$\ce{A + A -> P}$$ This review, suggests to express the rate in terms of the production of ...
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Catalysts and activation energy

Do catalysts increase rate of reaction only by decreasing activation energy? Or can they affect the Arrhenius factor or reaction orders? Like if one catalyst is more effective at increasing rate of ...
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3 answers
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Balancing reactions algebraic method limitations [duplicate]

How do I balance this reaction using the algebraic method? Seems that the equation can't be solved. How do I balance such reaction and does the algebraic method has limitations and wont work for ...
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4 votes
3 answers
273 views

Second order reaction with different reactants

In a laser photolysis reaction $\ce{C6H5NH2}$ $(C_0 = \pu{60 µM})$ is oxidized to its radical cation. The disappearance of the cation can follow three pathways: (1) Dimerzing of the cation, (2) ...
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-2 votes
1 answer
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Can iodine replace other halogen as well?

While reading about halogen family I encountered the reaction: $$\ce{NaClO3 + I2 -> NaIO3 + Cl2}$$ I know that that the oxidizing tendency of halogens decreases down the group, so I think that the ...
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-1 votes
1 answer
1k views

Find order of reaction 2A → B + C

Derive the integrated rate expression for a reaction of type: $$\ce{2A -> B + C}$$ I first need to determine the order of the reaction in order to find integrated rate law of that particular order....
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2 votes
1 answer
206 views

How is the Rate law of a reaction measured?

What is the Rate law of the reaction below? $$\ce{4 HBr + O2 -> 2 H2O + 2 Br2}$$ How do we approach finding the rate law of a reaction? Can this be found out only through experiments?
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