What is Reaction rates: Definition and 20 Discussions

The reaction rate or rate of reaction is the speed at which a chemical reaction takes place, defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per unit time. Reaction rates can vary dramatically. For example, the oxidative rusting of iron under Earth's atmosphere is a slow reaction that can take many years, but the combustion of cellulose in a fire is a reaction that takes place in fractions of a second. For most reactions, the rate decreases as the reaction proceeds. A reaction's rate can be determined by measuring the changes in concentration over time.
Chemical kinetics is the part of physical chemistry that concerns how rates of chemical reactions are measured and predicted, and how reaction-rate data can be use to deduce probable reaction mechanisms. The concepts of chemical kinetics are applied in many disciplines, such as chemical engineering, enzymology and environmental engineering.

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  1. O

    Off by order of magnitude when calculating how much calcium is in bone

    I think I have the answer, but when I calculate it out, I'm off by at least an order of magnitude. My process goes like this: The (looked up) specific activity of Ca-49 is ##1.63*10^7 TBq/g##, which is ##1.63*10^{16} KBq/g## The activity of the sample after 5 minutes rest is ##166KBq##, per...
  2. B

    A Entanglement in Ultracold Chemistry and Physics

    I'm looking for work published discussing the relationship between von Neumann entropy as well as entanglement with regard to chemical reactivity in the ultracold temperature scales. An article published under the title "Ultracold chemistry and its reaction kinematics" discussed this...
  3. N

    Average Reaction Rates Homework: Δ[A]/aΔt = Δ[ B]/bΔt

    Homework Statement Homework Equations Δ[A]/aΔt = Δ[ B]/bΔt The Attempt at a Solution Δ[ I]/3Δt = Δ[H]/2Δt = 7.8E-4. What exactly am I supposed to do for this?
  4. Revengeance

    Chemistry Lab Homework: Reaction Rates & Concentration Calculation

    Homework Statement Hello all, I am doing this lab http://scc.scdsb.edu.on.ca/Students/onlinecourses/Sikora/sch4u/v12/60.pdf i am stuck on trying to find hte concentration of ch3cooh Homework Equations n = m / M and c = n*vand i think the ideal gas law could be used but not sure The Attempt...
  5. ShellDough

    Question regarding the rate law of a reaction

    Homework Statement Data in the table were collected at 300 K for the following reaction: A(g) + B(g) → products Concentration of A 1.00 0.100 1.100 Concentration of B 0.100 0.100 1.00 Initial Rate (M/s) 1.29x10^-29 1.33x10^-30 1.30x10^-29...
  6. B

    Reaction rates, temperature, and thermal energy

    Homework Statement Hi there. My question is more for clarification than a homework question. In my studies, I noticed that my MCAT study manual provides problems relating reaction rates and the effect that temperature and thermal energy have on a reaction. For example, a question asks: in an...
  7. R

    Overall rate of reactions of decomposition of dimethyl ether

    Hi Guys, I'm solving this for almost a week, this is a part of our probset in chemical kinetics: The thermal decomposition of dimethyl ether: CH3OCH3 ---K1--> CH3' + OCH3' CH3' + CH3OCH3 ---K2--> CH4 + CH2OCH3' CH2OCH3' + --k3---> CH3' + HCHO CH3' + CH2OCH3' ---k4--> C2H5OCH3 using steady-state...
  8. B

    Reaction Rates: Concentrations vs Activities?

    If we want to be precise, should rate laws and corresponding ODEs correctly be expressed in terms of concentrations, or in terms of activities? In other words, are reaction rates really functions of concentrations, or of activities (which would make more logical sense) - and if the latter, why...
  9. P

    Why is the Reaction Rate Directly Proportional to Sulfuric Acid Concentration?

    The reaction I did for the lab is: H2SO4 + Mg --> MgSO4 + H2 In my graph, there displays the two variables - the concentration of sulfuric acid and the average rate of reaction in direct proportion. How do I explain the trend? I know I can explain this qualitatively using collision...
  10. G

    Does heat increase reaction rates?

    I thought heat increased reaction rates, meaning that when something is at equilibrium, it should increase both the forward and reverse reaction rates... Is this wrong? Then why does Le Chatelier's principle predict that a temperature increase favors the endothermic direction?
  11. L

    Quick Science Fair Question - Testing Enzyme Reaction Rates

    Hi! I was hoping someone could answer a quick question I had about science fair... I had talked to my teacher about doing a project where I test the reaction rate of enzymes in turkey giblets (see which chunk of the turkey has fastest/lowest reaction rates) but we didn't go into a lot of detail...
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    OCHEM transition states and reaction rates

    Homework Statement Explain why 2-bromopropane reacts with NaI in acetone over 10^4 times faster than bromocyclopropane. (Hint: examine the transition state for each of the reactions) Homework Equations The Attempt at a Solution I understand this is a sn2 type reaction and...
  13. Z

    Reaction Rates & Gases question

    Homework Statement In the gas phase methyl isocyanide (CH3NC) isomerizes to methyl cyanide (CH3CN) in a first order reaction with a rate constant of 7.70x10^-4s^-1 at 500K. An experiment is performed, where 25.0 torr of methyl isocyanide is placed in 23.2L container at 500K. After 520...
  14. R

    Reaction Rates Explanation?

    Experiments show that the following redox reaction is second-order overall: NO2(g) + CO(g) --> NO(g) + CO2(g) In the reaction, the initial [NO2] is twice the initial [CO]. What is the ratio of the initial rate to the rate at 50% completion? In the solution they say: [NO2]i = 2[CO]i...
  15. J

    Reaction Rates of NiOOH/H20 and Zn Reactions

    Please someone who can help me to find the reaction rates of these reactions NiOOH + H20 + 1e- <====> Ni(OH)2 + 0H- Zn ----> Zn 2+ + 2e- thanks to all
  16. N

    Solving Reaction Rates in Lab Experiments

    Homework Statement okay so I am going to do a lab on reaction rates, there's a table given (effects of varying concentration) there are 9 reactions, I will just give one, ( if i can figure this out ill figure out the rest on my own) so reaction #1 flask A contains 7.50mL of .200M KI...
  17. Y

    Question about activation energy and reaction rates.

    Homework Statement I know that temperature and kinetic energy are related, so as temperature increases the energy of the reactants as well as the amount of collisions and bonds formed, increases. I take this as meaning that the rate increases. But I also read in my organic book that in...
  18. N

    Enzymatic Reactions: Substrate, pH, & Heat Effects

    If you increase the substrate concetration, then the enzmatic reation will increas right? If you alter the pH affect of an enzymatic reaction,then the enzyme will denature right? are my concepts right ? also, If you pretreat an enzmye with high heat, how will it affect the rate?
  19. K

    Chemistry Problem - Reaction Rates

    I know this isn't a physics problem, but it's driving me crazy because I can't figure it out. >> The rate of a particular reaction doubles (2.0 X) when the temperature is increased from 25 C to 35 C. By what factor will the rate increase over the temperature interval of 118 C to 128 C? <<...
  20. M

    What Factors Affect the Measurement of Reaction Rates in a Closed System?

    I came across this question on one of the practice papers I have and isn't sure about the answer, any help would be appreciated. The following reaction occurs at constant temperature and constant volume in a closed system: CaCO3(s) + 2H(ion)(aq) + 2Cl(ion)(aq) -> CO2(g) + H2O(l) +...