Questions tagged [rate-equation]
The rate-equation tag has no usage guidance.
57
questions
-1
votes
2
answers
54
views
How to write a rate expression when one reactant is not soluble?
For a chemistry experiment, I would like to determine the rate expression for the reaction between zinc and hydrochloric acid. Given that zinc is not soluble in the water, would I use a "false&...
- 19
-1
votes
2
answers
33
views
Solving for Partial Pressure given first-order decomposition
From my GenChem practice exam:
Consider the following reaction:
$\ce{C4H8 (g) → 2C2H4 (g)}$
The first-order decomposition of cyclobutane to two molecules of
ethene has a rate constant of $\ce{9.20\...
- 251
0
votes
0
answers
24
views
Estimate scaled up rate of gas phase reaction
I have measured the conversion rate of a particulate-catalyzed gas phase reaction in a reactor. That is, I have a graph of how fast $\pu{1 mol}$ of catalyst converts $\pu{1 mol}$ of reactant into $\pu{...
- 111
1
vote
1
answer
107
views
Calculating rate constant for reaction between potassium permanganate and oxalic acid
I'm writing a lab report investigating the effects of temperature on the rate constant in the reaction between potassium permanganate and oxalic acid. For my practical I've measured the time of colour ...
- 181
0
votes
2
answers
82
views
Reaction rate derivation: amount of substance vs concentration [closed]
Let's say you have the reaction
$$A + B \; \rightarrow \; C.$$
I would like to understand why $\frac{\mathrm{d}[C]}{\mathrm{d}t}$ is proportional to $[A][B]$. I can see why
$$\frac{\mathrm{d}n_C}{\...
- 11
1
vote
0
answers
78
views
Can the overall order of a reaction ever be strictly less than $1$?
In A-level chemistry we are taught that:
To every reaction: $$\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}$$...
- 175
3
votes
1
answer
240
views
Concentration of products in tank reactor
I want to calculate the concentrations of all components in the outlet stream of the reaction: C$_2$H$_6$ -> C$_2$H$_4$ + H$_2$ (A -> B + C)
I have a tank reactor (isothermic and isobar): V= $...
- 1,069
2
votes
1
answer
88
views
Reversible monomolecular reaction with two reverse rates
I think this is a simple problem but my kinetics are terrible and I was hoping for some assistance following up on the work of a previous student. I'm open to any form of assistance and I hope this ...
1
vote
1
answer
38
views
Dependence of rate on the nature of reactants and other factors
Consider a reaction
$$\ce{aA + bB -> cC + dD}$$ whose reactants are given by A and B and the products are C and D.
The rate of this reaction is given by $$\frac{dx}{dt} = -\frac{d[\ce{A}]}{adt}= -\...
- 281
0
votes
1
answer
85
views
How do we know that rates depend on the product and not the sum of reactant concentrations [closed]
I've been struggling to understand the mathematics behind the calculation in enzyme kinetics within systems biology at an intuitive level.
Every research article and textbook says it is based on the ...
- 117
2
votes
1
answer
130
views
Differential equation in consecutive reactions
I'm blocked in a step of getting to the equation $(7)$, more precisely in the step between $(5)$ and $(6)$. I show my way to solve it down, but I don't get the same as $(6)$, so I wanted to know if I ...
- 1,009
0
votes
1
answer
97
views
PFR reactor: -1/r vs conversion plot
A generic reagent A is considered. The behavior equations of a CSTR reactor is the following:
$$
\tau = c_\mathrm{A,0} \intop_0^{X_\mathrm{A,final}}
\dfrac{1}{-r_\mathrm{A}} dX_\mathrm{A}
$$
where $\...
- 261
1
vote
1
answer
124
views
Serial reactions or consecutive reactions: rate vs time
Serial reactions, or consecutive reactions, are two or more reactions in which the product of the first reaction becomes the reactant in the next. The simplest case of a serial reaction involves a ...
- 261
-1
votes
1
answer
44
views
How does the stoichiometric coefficient affect the time until a given percentage of the reactant is consumed (if at all)?
Problem from Serway's College Physics test bank:
The reaction $2NO_2\rightarrow2NO+O_2$ obeys the rate law:
$\large \frac{\Delta[O_2]}{\Delta t} = (1.40\times10^{-2})[NO_2]^2 \space at \space 500^\...
- 173
0
votes
0
answers
38
views
How to rewrite kinetic mass balance to get to proper SI units?
Suppose from kinetic mass balance I get the following differential equation of the molarity substances $A$,$B$, and $C$ in a reactor, with molar in- or outflow rate $\phi$, and rate constant $k$:
$$
\...
- 11
0
votes
0
answers
36
views
What are the reaction rate constants, or coefficients, of coal combustion at high temperature?
Say I have coal that I will combust with $\ce{O2}$ at a high temperature of $\pu{1600-1800 K}$, what are the reaction rate constants, or coefficients, of the main reactions?
I have searched around ...
- 11
-2
votes
3
answers
95
views
In regards to the Gibbs free energy equation, it seems that the two terms oppose one another, Enthalpy and -TS. Can you explain this?
So for example, if H is endothermic, then the enthalpy term is positive, meaning energy is absorbed by system overall, meaning net bonds broken, meaning the equation leans towards nonspontaneity. If ...
- 1
2
votes
1
answer
155
views
Rate order when the slow step only contains intermediates?
I feel a bit sheepish asking this, but I was told that the stoichiometry of the slow step of a mechanism indicates the order of a reaction with respect to a reactant. However, in the slow step of this ...
- 663
2
votes
1
answer
51
views
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, ...
- 29
3
votes
1
answer
134
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 ...
- 1,069
0
votes
1
answer
246
views
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:
...
- 1,069
1
vote
1
answer
100
views
pH for optimal kinetic for enzyme reaction
If I am given the following enzyme reaction:
where K$_{EH,1}$=K$_1$ = $10^{-4}$ and K$_{EH,2}$=K$_2$ = $10^{-8.2}$. Iwant to calculate at which pH I have the optimal kinetics by calculating $\frac{v'...
- 1,069
0
votes
0
answers
54
views
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 ...
- 1,069
0
votes
0
answers
77
views
Tmax of parallel reactions/Steady state reactions
Below are four reactions, to this experiment inhibitor is added so that k$_3$ = $0$ (but the other reactions are unaffected) calculate [D] when the reaction is over. The initial concentration of A is $...
- 1,069
0
votes
1
answer
1k
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 ...
- 17
1
vote
1
answer
177
views
How to calculate rate of carbon dioxide from rate equation? [closed]
The concentration of carbon dioxide that changes with time:
$$\ce{CO2(g) + H2O(l) <=>[$k_\mathrm{fwd}$][$k_\mathrm{rev}$] HCO3-(aq) + H+(aq)}$$
How to calculate the integral for the following ...
- 11
0
votes
0
answers
29
views
Can two 1st order reactants in an overall 2nd order reaction have different rates?
I've recently done a saponification reaction of ethyl acetate with sodium hydroxide and used the initial rates method to find the order of reaction. (I change the concentration of one reactant and ...
- 27
-1
votes
1
answer
127
views
Rate equation for the decomposition of hydrogen peroxide with iron(III) chloride as catalyst [duplicate]
I am trying to determine the activation energy of the decomposition of hydrogen peroxide with iron(III) chloride added as a catalyst. To do that, I need to find the rate constant, but I am not sure ...
3
votes
2
answers
227
views
Does 'k' in the rate law change with a change in volume
I'm a high school AP Chem student and we recently learned about the rate law and the Arrhenius equation. In school, we learned that rate constant 'k' is only changed with temperature or catalyst. ...
- 103
-1
votes
1
answer
332
views
Rate of Reaction - Potassium Permanganate and Hydrogen Peroxide
I'm interested in an aerospace project that requires I know the reaction rate ($[\pu{M/s}]$) of,
$$\ce{2 KMnO4 (aq) + 3 H2O2 (aq) -> 3 O2 (g) + 2 MnO2 (s) + 2 KOH (aq) + 2H2O (l)}.$$
I'm just ...
10
votes
1
answer
269
views
Are there any genuine, elementary ternary reactions?
Macroscopically, reaction rates can be of varied order. But mechanistically, most reactions are first-order or second-order/binary (e.g. SN2, many catalyst surface reactions, dimers). Most processes ...
- 261
-1
votes
1
answer
326
views
Writing rate of disappearance and rate of appearance using rate law [closed]
I have studied that rate of disappearance and rate of appearance is the change in concentration of reactants and products (respectively) with respect to time. Thus,
$$\text{ROD} = -\frac{\Delta c_R}{\...
- 177
0
votes
0
answers
586
views
Assuming 2O3 (g) → 3O2 (g), how much oxygen will be formed within 5.50 s for a reaction rate of 0.250 M/s?
Context: The rate of appearance of $\ce{O2}$ in the reaction: $\ce{2O3 (g) -> 3O2 (g)}$ is $\pu{0.250 M/s}$. So, over the first $\pu{5.50 s}$, will it form $\pu{1.38 M}$, or $\pu{4.13 M}$ of oxygen ...
-1
votes
2
answers
1k
views
What is the rate law of a reaction: 2A + 3B → products? [closed]
Update: I found out that the coefficients of the chemical reaction are not the exponents in the rate law. It is actually the order of the species during the reaction.
It is known that in the reaction, ...
0
votes
1
answer
92
views
Problem understanding the rate of reaction of reversible reactions
Case 1:
$$\ce{CH_3COOH + NaOH<=>CH_3COONa + H_2O}$$
At equilibrium, there remain extremely small concentrations of the reactants (acetic acid and sodium hydroxide), and comparatively large ...
- 23
3
votes
0
answers
35
views
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 ...
- 31
0
votes
1
answer
322
views
Can an elementary reaction have zero order?
I am very confused right now about my approach to this question could somebody help me out with this. I reasoned my answer as given below
Let's assume if a complex reaction is of zero order. It ...
user117301
0
votes
1
answer
186
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 ...
- 1,069
1
vote
0
answers
140
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 $1$. $\...
- 1,069
0
votes
0
answers
106
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 ...
- 1,069
8
votes
4
answers
389
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}...
- 1,789
6
votes
2
answers
386
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.: ...
- 1,765
0
votes
1
answer
68
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 ...
- 11
2
votes
1
answer
139
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)} &\...
- 31
5
votes
2
answers
118
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
3
votes
0
answers
76
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 ...
- 31
4
votes
1
answer
188
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
0
votes
1
answer
1k
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? ...
- 3
4
votes
2
answers
2k
views
Determine vmax and enzyme concentration (Michaelis–Menten)
I am given that the enzyme concentration is $\pu{15 nM}$ and the following data:
$$
\begin{array}{rl}
\hline
S/\pu{mM} & V/\pu{mM s^{-1}} \\
\hline
1 & 0.202 \\
2 & 0.368 \\
5 & 0....
- 1,069
3
votes
1
answer
108
views
First or second order reaction
I have that $100$ mM of K$_3$Fe(CN)$_6$ is dissolved in equimolar of the organic ion (which I assume is HCN). In the solution Fe(CN)$_6$$^{3-}$ reacts to form Fe(CN)$_6$$^{4-}$.
The formation of Fe(CN)...
- 1,069