What is Activation: Definition and 105 Discussions

Activation, in chemistry and biology, is the process whereby something is prepared or excited for a subsequent reaction.

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  1. G

    Calculation of activation with mesh tally in MCNPX 2.6

    Hi, All! Can anyone help me to construct a card for calculation of a spatial activation? Reaction is 27Al(n,p). I used a tmesh card for calculation of neutron flux as: tmesh rmesh21:n flux cora21 190 9i 210 corb21 -10 9i 10 corc21 -10 9i 10 ergsh21 0 20 endmd Somewhere in a problem I...
  2. Wrichik Basu

    Activation of Network Connection failed on Ubuntu 20.04

    I am facing this issue since some months on my laptop running Ubuntu 20.04. The WiFi disconnects suddenly and cannot reconnect, and an error message is shown in the Notification saying "Activation of Network Connection failed." This is not a problem with the router because just a few days back...
  3. O

    Rhodopsin Phosphorylation Activation

    While glancing through an ophthalmology textbook several years ago, I learned that the transition between the two forms of rhodopsin (that results in neural activation and, ultimately, vision) can be accomplished through the electromagnetic energy provided by certain radio wave frequencies (and...
  4. HelloCthulhu

    PEM electrolyzer - How does platinum reduce activation energy?

    I've been researching pem electrolyzers, but still don't understand how to mathematically express how platinum reduces the activation energy necessary to dissociate H2O. I've seen the Arrhenius equation solved before, but didn't understand how to get the values for it. Here are the operating...
  5. TytoAlba95

    Lowered activation energy in enzymatic reactions

    I was stuck with a question; how does enzyme lower the activation energy of a reaction. After several internet searches, I found a post in biostackexchange which partially clarified my question. I'll write my current understanding before I proceed to my actual question. Activation energy is the...
  6. V

    Activate ZnS: Ag ppm Explained

    What is the mechanism that explains the activation of ZnS with less than ppm of Ag? Bibliography from the 50’s mention of 10-7 parts of Ag in weight in order to activate the ZnS.
  7. C

    Relationship between activation energy and melting?

    Hello. I know this is a dumb question but I am just learning chemistry. Ok, for collision theory, atoms need a certain amount of energy to bond, because they need to break old bonds and form new ones. Makes sense But, at high temperatures, things become gaseous. At low temperatures, things...
  8. C

    A Monte Carlo script to simulate the activation and decay of cobalt

    Homework Statement A sample of cobalt was previously measured in a neutron scattering experiment. As a result, the sample has become activated. Write a Monte Carlo script to simulate the activation and decay of a Co sample during and after a neutron scattering experiment. It is recommended to...
  9. BillTre

    Thermo Activation of Individual Neurons in Live Vertebrates

    A very cool new molecular neuro trick Here's some background and a loose summary. Here is the main reference (surprisingly openly available!). In recent years, neurobiologists have been able to get neurons to make particular proteins by various means (such as filling the cells or in someway...
  10. S

    I What is the point of a spacer in neutron activation?

    I'm just reading over some experimental notes for neutron activation analysis and I see the mention of a spacer being placed between the irradiated sample and the detector face. What does a spacer actually do? I did a quick google but couldn't really find anything.
  11. Kashif

    MCNP Secondaries (PWR Coolant activation)

    I have to calculate the gammas produce due to oxygen activation in the coolant of PWR reactor core. the tally i used is F4 and FM.. but the problem is in core their are different cells within a cell. so how to specify the required cell . i have selected the whole core as a cell and then specify...
  12. Icy98

    Activation energy for chemical reaction

    Only particles that possesses enough energy to overcome the activation energy and orientated correctly will collide and form products. How about those particles which do not possesses enough kinetic energy to overcome the activation barrier? Does it mean that for a particular chemical reaction...
  13. wronski11

    Specific and surface activity of nuclear waste

    Dear all, I am looking for more information how specific activity \frac{Bq}{g} and surface activity \frac{Bq}{cm^2} is measured. This is done to determine whether the materials of interest can be treated as harmless and disposed as usual waste. I am interested how the experimental procedure...
  14. S

    Defintion of Neutron activation and moderation

    When the teacher is asking for the definition of "Neutron activation and moderation" does he mean it together or separate. I google the quoted word but it gives "Neutron activation analysis". Is this the same thing or do I look separately the word "Neutron activation" and then "Neutron moderation".
  15. A

    Fusion Activation: Analysis & Calculation | Why Needed?

    Hello Everybody i hope you all will be fine, can some one tell me about the activation analysis of fusion? why Activation is needed in Fusion reactor? what methodology can be used for this calculation?
  16. Logic Cloud

    Activation and deactivation of proteins

    I have come to understand that phosphorylation plays a significant role in the (de)activation of certain proteins. I'm now trying to understand this mechanisms in more detail. Specifically, how the addition of a phosphate group can regulate protein activity. Can anyone point me to a source where...
  17. D

    Activation energy and pre exponential factor

    Homework Statement Calculate activation energy and pre exponential factor, i need help with the pre exponential factor Homework Equations Temperature °C -20 = 253 k -10= 263 0=273 10=283 20=293 Rate const. s-1 1.15 3.85 11.3 28.7 74.0 The Attempt at a Solution i already plotted the graph on...
  18. K

    A Activation Energy of Amorphous Transition Metal Oxides

    Hi, Is measuring the temperature dependent conductivity a reliable way of determining the activation energy/ the dopant level of a wide band-gap transition metal oxide. Also does the activation energy in this case change with the dopants density. Thanks.
  19. P

    Activation energy question

    Could someone help me figure out the activation energy of a urea hydrolysis reaction when catalyzed by urease?
  20. G

    Methods of Regulating Proteins

    I have been looking into different methods of regulating protein activity for a project. I think it is pretty interesting and I want to learn more about this. I want to learn about the different methods out there, if you know of any cool or helpful regulation techniques I would certainly...
  21. A

    Activation energy of parallel reaction

    Well,I know that the activation energy of a parallel reaction can be determined by the arrhenius equation as (e1k1+e2k2)/(k1+k2) where e1,k1 and e2,k2 are the activation energies and rate constants for the two reacations.now consider the reaction A》B,and A》C since at every instant the reacted...
  22. S

    Photonuclear activation of ground

    Which energy gamma rays would significantly activate ground and buildings? The most sensitive stable isotopes for photonuclear reactions are Be-9 and D. The reactions are Be-9+hnu->2*alpha+n, threshold 1,67 MeV, followed in air by N-14+n->C-14+p where C-14 is radioactive, and d+hnu->p+n...
  23. 8008jsmith

    Standard Free Energy of Activation of a Reaction

    Homework Statement The standard free energy of activation of a reaction A is 83.7 kJ/mol at 298K. Reaction B is 10 million times faster at the same temperature. The products of each reaction are 10 kJ/mol more stable than the reactants. (a) What is the standard free energy of activation of...
  24. S

    Change in Enthaply and Activation Energy

    Homework Statement For a reaction that is exothermic in the forward direction, can the activation energy Ea(fwd) ever be less than the enthalpy change? Homework Equations Endothermic equation: Ea(rev) = Ea(fwd) - deltarH The Attempt at a Solution [/B] The answer in the book has "yes", but...
  25. B

    Enthelpy and activation energy statements

    Homework Statement For a particular reversible reaction, the forward process is exothermic and the reverse process is endothermic. Which of the following statements must be true about this reaction? (A) The forward reaction will be spontaneous under standard conditions (B) The reverse reaction...
  26. B

    Enthelpy and activation energy

    Homework Statement This question is just for an overall understanding of enthalpy and activation. My book states that catalysts decrease the activation energy of a reaction. This makes sense. However, how does this change the enthalpy? If a catalyst creates a new pathway, wouldn't the...
  27. W

    Safety match activation energy

    I saw a YouTube video where someone took nichrome wire and a high voltage source and managed to light a whole series of matches. I got me curious so I ran some numbers on how much wattage could be produced for a given length of nichrome wire and a given voltage. And assuming time is no issues...
  28. W

    What is the activation energy for a match?

    I saw a YouTube video where someone took nichrome wire and a high voltage source and managed to light a whole series of matches. I got me curious so I ran some numbers on how much wattage could be produced for a given length of nichrome wire and a given voltage. And assuming time is no issues...
  29. N

    Minimum solenoid activation time?

    Heey guys, I have a problem. I want to calculate the minimum time i have to activate a (latching)solenoid so that its final velocity is 0 m/s when it hits the inside. Well I know the following things: F= m*a I know the force and the mass, so a can be calculated. V = a*t. the average...
  30. K

    Can O2 combine with H2 to form water without activation energy?

    Let say that I have hydrogen gas and oxygen gas mix together, is there any chance that some H2 and O2 will react to form water without doing anything to it? I know that there needs to be activation energy to start the reaction, but are there any chance of reaction happening without activation...
  31. S

    Mechanism of benzene nucleophilicity activation

    I have some questions how various substituents are transfering benzene conjugated (π) electrons (i.e. activating/deactivating). As usual, no chemist provides an explanation. 1)As I see, the first important thing when forming a carbocation during electrophilic aromatic substitution is to find...
  32. D

    Energy of Activation Clarification

    In transition state theory, the energy of activation (E) shows up in the Arrenhius equation as: k=Ae^(-E/RT). Does this energy of activation term correspond to internal energy? Or is it some other type of energy (i.e. Gibbs, Helmholtz)? I know its not Gibbs because that appears in the Eyring...
  33. F

    Calcualting Activation Energy using Arrhenius equation and plot

    This is part of a lab report so not sure if the template agrees with what I am asking but basically using the Arrhenius equation in the form of ln(k)=ln(A)+(\frac{-E_a}{R})(\frac{1}{T}) I plotted a straight line graph of ln(k) vs 1/T and found the gradient to be -5525. Its the units that are...
  34. K

    Calculating Activation Energy of Crystal Violet/NaOH Reaction

    So we just completed an experiment and we are now expected to calculate the activation energy of the reaction we ran using our data. The reaction was between crystal violet and sodium hydroxide. The reaction was performed under pseudo order conditions (sodium hydroxide concentration did not...
  35. A

    What is the difference between gibbs free energy and activation energy

    what is actually meant by gibbs free energy and what is the difference between gibbs free energy and activation energy?In an enthalpy diagram how can it be denoted(just like for activation energy is denoted by the energy difference between transition state and reactants' enthalpy)?I just search...
  36. S

    Optimizing Activation Coil Selection for Maximum Gamma Flux

    What is best way to figure out which of these activation coils would yield a higher gamma flux: 27Al, 58Ni, and 115In. I have a PuBe neutron source, which I am told to just use a 4.5MeV neutron-energy. I am running MCNP calculations to find flux at a point away from the foil. I knows the...
  37. I

    Calculating Co-60 Produced from Co-50 in 1 Week

    Co-60 is produced from Co-50 through neutron activation. Neutron flux 10^18 nuetrons/(s*m^2). cross section is 20 barns and the mass of Co-50 40mg. How many Co-60 are produced in one week? My attempt: I multiplied the flux by the seconds in one week and by 20 barns in m^2 and got 0.0122...
  38. N

    Why does a higher activation energy usually mean a slower reaction?

    Why does a higher activation energy usually mean a slower reaction? Doesn't activation energy just tell us whether or not a reaction will take place or not based on if the particles have enough energy to meet the activation barrier? How is it related to the rate of the reaction?
  39. L

    Controlling activation of a circuit with a moisture meter

    Hi, I'm building a make shift spectrophotometer. It's only concerned with a narrow bandwidth of visible light. I'm using two LEDs, one which is lit, the other which is co-incident with a sample in between absorbing light from the lit LED. I pass the voltage of the receving LED to an LM358...
  40. Saitama

    What is the Activation Energy for Juice Spoiling?

    Homework Statement At room temperature (20°C) orange juice gets spoilt in about 64 hours. In a refrigerator at 3°C juice can be stored three times as long before it gets spoilt. Estimate (a) the activation energy of the reaction that causes the spoiling of juice. (b) How long should it take...
  41. P

    Arrhenius plot and activation energy

    Hi,guys. I m trying to determine activation energy of donor levels . So i have measured absorption at different temperatures of my sample (mono-crystal) And I have plotted ln(optical density) vs 1/T(K). And I want to calculate activation energy useing D=D0exp(-Ea/kT) In plot above...
  42. V

    Muscle Activation Techniques ?

    "Muscle Activation Techniques"? I'm working on getting more physically active and fit, and I've received a recommendation for a (patented, naturally) exercise program (or perhaps "paradigm" is a better word) called "Muscle Activation Techniques" (main site). I know there's a lot of BS in the...
  43. B

    The thermal activation cross section of H-3,C14

    I am doing a research on activation radionuclides resulting from thermal neutron(2200 m*s-1 or 0.0253eV) capture. The activation cross section of some nuclides(H-3,C-14,54Mn,58Co), still can't be found even many efforts were taken. The related reactions...
  44. C

    Activation energy from dynamic NMR

    Homework Statement I need to calculate the activation energy (barrier of rotation) of an amide bond. I have NMR spectra at various temperatures. I know that once I have the rates I can do an Arrhenius plot to find the activation energy, but I'm having trouble with the ``finding the rates''...
  45. G

    Activation energy/bond enthelpy

    I'm doing A level Chemistry, and my teacher isn't good at explaining things. I know activation energy is the minimum energy required for a reaction to take place - so is that just the energy required to break the original bonds? And is the activation energy for a particular bond to form the same...
  46. H

    Half life and activation energy

    Homework Statement I have two questions that I just don't even know where to start The activation energy for the reaction CH3CO CH3 + CO is 71 kJ/mol. How many times greater is the rate constant for this reaction at 170°C than at 150°C? A) 0.40 B) 1.1 C) 2.5 D) 4.0 E) 5.0 and A...
  47. A

    Chemical Kinetics - Activation Energy and gr

    The problems are Number 12 and 13 on this link http://isites.harvard.edu/fs/docs/icb.topic1096438.files/PS4.pdf I have the value of k for sum number 12, it is 1.54*10^-4. Im completely stuck with number 13 cos I'm unfamiliar with that concept and it kinda went over my head in lecture...
  48. S

    Bond energy and activation energy

    Is the energy required to break the bonds of a compound in order for the reaction to occur (bond energy) the same as activation energy? Thanks for the help! :smile:
  49. H

    Need help, Activation energy determination from this reaction. Is this possible?

    Need help, Activation energy determination from this reaction. Is this possible?? i did an experiment, i noted the tempreture and found rate constant. My friend did the same experiment and she found rate constant and noted the tempreture.. The tempreture differs by one degree. Can i calculate...
  50. H

    Help I need to find out whether activation energy can be calculated this way ?

    i did an experiment, i noted the tempreture and found rate constant. My friend did the same experiment and she found rate constant and noted the tempreture.. The tempreture differs by one degree. Can i calculate tempreture like this...? S2O82-(aq) + 2 I-(aq)  SO42-(aq) + I2(aq)...