What is Kinetics: Definition and 254 Discussions

Chemical kinetics, also known as reaction kinetics, is the branch of physical chemistry that is concerned with understanding the rates of chemical reactions. It is to be contrasted with thermodynamics, which deals with the direction in which a process occurs but in itself tells nothing about its rate. Chemical kinetics includes investigations of how experimental conditions influence the speed of a chemical reaction and yield information about the reaction's mechanism and transition states, as well as the construction of mathematical models that also can describe the characteristics of a chemical reaction.

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  1. Telemachus

    Rigid body kinetics in 3 dimension space

    I need some help with the equation of moments for this exercise: Each wheel of an automobile has a mass of 22 kg, a diameter of 575 mm, and a radius of gyration of 225 mm. The automobile travels around an unbanked curve of radius 150 m at a speed of 95 km/h. Knowing that the transverse distance...
  2. W

    How Do You Calculate the Frictional and Coupling Forces for a Skidding Truck?

    1.The 2-Mg truck is traveling at 15 m/s when the brakes on all its wheels are applied, causing it to skid for a distance of 10 m before coming to rest. Determine the constant horizontal force developed in the coupling C, and the frictional force developed between the tires of the truck and...
  3. F

    Vapor pressure of water (kinetics)

    Hi All, I tried to collected hydrogen gas generated from the reaction between a metal and hydrochloric acid. I put a inverted conical flask in the water, and the generated H2 would push the water out of the flask, and then the H2 was collected. However, I guess there is water vapor mixed...
  4. S

    Why is the denominator of the ratio possible if the forward rate is 2nd order?

    In my textbook there is an example with the following reaction and rate: C6H6 + 3H2 -> C6H12 Rf = kf[C6H6][H2] Then the the example claims that the ratio of the rate constants is: kf / kr = [C6H12] / ( [H2]3 [C6H6] ) How is the denominator of that ratio possible if the forward...
  5. S

    Kinetics of Particles work and energy; A moving car

    Homework Statement The 2Mg (i assumed mega-gram, not sure if that is the correct term) car has a velocity of v= 100km/h when the driver sees an obstacle in front of the car. If it takes 0.75 s for him to react and lock the brakes, causing the car to skid, determine the distance the car...
  6. H

    Enzyme Kinetics and Affinity

    Homework Statement One plant species grows on soil with low concentration in potassium and a similar species is adapted to growing on soil with high concentration in potassium. In their root cells, potassium transporters move potassium into the cell. THe potassium transporters of which plant...
  7. J

    Newtons 2nd Law & Kinetics pt. 2

    Homework Statement A 500kg crate is pushed with a 2000N force. The force of the sliding friction acting on the crate is 1900N. How fast will the crate be moving after 10 seconds? How far will it have moved in this time? Determine the net force Homework Equations a = \SigmaF/m...
  8. Z

    Chemical Kinetics Advanced Problem

    Homework Statement Consider a first order decomposition reaction 2P(g) -----> 4Q(g) + R(g) + S(l) taking place at a temperature T. After 30 minutes from the start of the decomposition in a closed vessel, the total pressure developed is found to be 317 mmHg and after a long time, the...
  9. A

    Chemical Kinetics: 2A to C Reaction Rate Law

    So, let's say we have an elementary reaction: 2A --> C The rate of this reaction is (according to IUPAC: http://goldbook.iupac.org/R05156.html) - \frac{1}{2} \frac{d[A]}{dt} = k [A]^2 If we integrate this we get a certain integrated rate law (second order) However, if we multiply all of...
  10. B

    Chemical Kinetics: do not understand anything

    Homework Statement Our chemistry teacher just learned about chemical kinetics. I've been working with the calculus teacher to find out how to determine instantaneous rates exactly. We don't have any equation. Could someone explain this please? Homework Equations The Attempt at a...
  11. D

    Are you positive about part 2 in Helicopter Kinetics and Motion

    Homework Statement A helicopter is flying in a straight line over a level field at a constant speed of 6.8 m/s and at a constant altitude of 9.9 m. A package is ejected horizontally from the helicopter with an initial velocity of 11.0 m/s relative to the helicopter, and in a direction...
  12. C

    Help with kinetics and conservation problem thanks

    An object of mass m1 moving with velocity v1 in three dimensions collides with a second object of mass m2 moving with velocity v2. We are interested in solving for the velocities of the objects after the collision. There are six unknown values f (v1x)f ; (v1y)f ; (v1z)f ; (v2z)f ; (v2y)f ...
  13. W

    Chemical Kinetics: Rate Laws, Orders

    Homework Statement I understand how to determine the order of a rxn based on a series of experiments one divides one into another to obtain a ratio and then determines the power to which one is raised to determine the order. Typical data collected would be: Ex1 [A] .2 mol = Initial rate...
  14. G

    Dynamics Question (Kinetics& energy)

    Homework Statement The two blocks are connected by a light inextensible cord, which passes around small massless pulleys as shown below. If block B is pulled down 500 mm from the equilibrium position and released from rest, determine its speed when it returns to the equilibrium...
  15. Z

    Suicide substrate and kinetics

    Suicide substrate. An Enzyme, E reacts with a substrate S to form an enzyme substrate-complex, ES is usual for Michaelis-Menten kinetics. However, the substrate in the enzyme-substrate complex chemically reacts with the enzyme to form a permanent covalent complex at the enzyme active site. The...
  16. R

    How Do You Calculate Fragment Velocities Post-Explosion in Projectile Motion?

    Homework Statement A 4-kg projectile travels with a horizontal velocity of 600 m/s before it explodes and breaks into two fragments A and B of mass 1.5 kg and 2.5 kg, respectively. If the fragments travel along the parabolic trajectories shown, determine the magnitude of velocity of each...
  17. M

    Quadratic Equations and kinetics

    Homework Statement Find the time required for a train to reach 100m if V0=20m/s and acceleration is 0.5m/s2 Homework Equations s=v0t+(1/2)at2 The Attempt at a Solution i am not sure of how to go about getting s=(20)t+(1/2)0.5t2 into quadratic form for use in the quadratic formula...
  18. A

    Understanding Chemical Kinetics: Troubleshooting Common Questions in the Lab

    I am having a problem with my kinetics lab. There are just three questions I can not understand. 1. Determine the order with respect to HCl. Explain. 2. Determine the order with respect to Sodium Thiosulfate. Explain. 3. Why rate values for this experiment not adequate to achieve an accurate...
  19. S

    Differential v. Integral Rate Laws; Kinetics

    I'm nearing the end of AP Chemistry, and in review for the big test I came across my old friend, Chemical Kinetics. Also being near the end of Precalculus, the "differential" and "integral" laws piqued my interest. Remembering that I have not taken any Calculus lessons, can someone help...
  20. R

    Solve Kinetics, Springs: Find Collar Velocity at s=1 ft

    Homework Statement The 2-lb collar C fits loosely on the smooth shaft. If the spring is unstretched when s = 0 and the collar is given a velocity of 15 ft/s, determine the velocity of the collar when s = 1 ft. Homework Equations F = kx The Attempt at a Solution x = l-l0 = (√[1 + s2] - 1)...
  21. R

    Kinetics, force and acceleration

    Homework Statement The crate has a mass of 80 kg and is being towed by a chain which is always directed at 20º from the horizontal has shown. Determine the crate's acceleration in t = 2 s if the coefficient of static friction is μs = 0.4, the coefficient of kinetic friction is μk = 0.3, and...
  22. J

    Chemical Kinetics (Reaction Mechanisms)

    Can anyone please explain to me what is reaction mechanisms and intermediate? I have read my book many times, but I don't get it. Also, it would be great if you can me some examples about them. Thank you for your help!
  23. O

    Hypothetical kinetics questions, just for fun

    Some imagination is required, so let me dress up the question a bit. Imagine Spider-Man is on a rooftop, and he shoots a web to the top edge of a nearby building that's taller than the one he's on, in an attempt to swing toward it. Assume that the web is non-elastic and is completely adhered...
  24. T

    Kinetics in chemical reactions

    Can a catalyzer in a reaction be an intermediary as well? Im not sure, i don't think because it would have to consume it self...
  25. T

    Chemical Kinetics: Reaction Mechanism (My working attempt shown)

    Homework Statement 1. According to the mechanism below, what is the correct expression for the rate of consumption of A? In the mechanism, M is a molecule that collides with A and A* is a highly-energized form of A. Step 1 (reversible): A + M <---> A* + M rate constants k1 and k-1 Step...
  26. T

    Chemical Kinetics: Reaction Mechanism

    Homework Statement 1. According to the mechanism below, what is the correct expression for the rate of consumption of A? In the mechanism, M is a molecule that collides with A and A* is a highly-energized form of A. Step 1 (reversible): A + M <---> A* + M rate constants k1 and k-1 Step...
  27. D

    Kinetics of Masses on an Inclined Plane: Explaining Different Movements

    Homework Statement Refer to the diagram. can someone explain why is the 300lb block moves only one-half the distance of the 200lb then the acceleration and velocity also to one half. Homework Equations The Attempt at a Solution
  28. G

    Research in anomalous kinetics using fractional calculus

    Hi everyone, this is my first post on PF (yaay!). I hope this is in the right forum, if not I don't mind a mod moving this. I'm an undergrad physics student and one of my professors has hired me as a research worker over the summer break. Has anyone here done any work on fractional calculus...
  29. S

    Dynamics: planar kinetics of a rigid body (impulse and momentum)

    Homework Statement http://img340.imageshack.us/img340/7379/87835960.png r_{i}=.3 m \text{ and } r_{o}=.9 m The spool has a weight of 300N and a radius of gyration k_{O} = .45 m. A cord is wrapped around its inner hub and the end subjected to a horizontal force P = 50N. Determine the spool's...
  30. H

    Chem Kinetics: Suggestions for Further Reading & Calculus-Based Texts

    I've been independantly studying chemical kinetics from a standard freshman year chemistry textbook, and I enjoy the subject, could anyone suggest any further reading or sources? Specifically I'd like to try and find a calculus based text, as the one I have specifically avoids using any...
  31. G

    How Do You Calculate the Kinetics of a Suspended, Unwrapping Cylinder?

    Well, I had a couple problems on my final I was hoping to go over- hope nobody minds. Here's the first. Homework Statement A uniform cylinder of radius r and mass m, wrapped around by an unstretchable and massless string, is suspended from a point. The cylinder comes down unwrapping the...
  32. W

    Kinetics Problem: Finding average normal force

    I'd just like to say thank-you in advance for any and all answers. It is greatly appreciated. :smile: Homework Statement The 2kg ball is thrown at the suspened 20kg block with a velocity of 4m/s. If the time of impact between the ball and the block is 0.005s, determine the average...
  33. V

    Q in dynamics, kinetics, Energy

    Homework Statement 1 Kg block slides on a circular rod (no friction) from rest in A position by a force of 40N. What is the speed when it reached point B. (see attached pic) Homework Equations W(f)=E(B)-E(A) The Attempt at a Solution The energy in A is 0, the energy in B is...
  34. A

    First-Order Kinetics and Activation energy

    Homework Statement I already have an answer I'm just not sure if it's correct. This is done mostly graphically I just need to known if anyone else thinks it makes sense. Given this data: what is the rate constant, K, for each reaction, half life of each reaction and activation of the...
  35. Y

    Kinematics of a Slender Bar with Constrained End Rollers

    Homework Statement The small end rollers of the 3.6 kg uniform slender bar are constrained to move in the slow, which lies in a vertical plane. A the instant theta=30 the angular velocity of the bar is 2 d/sunter-clockwise. Determne the angular acceleration of the bar,k the reaction at A and...
  36. Y

    How Much Vertical Acceleration Can a Forklift Give Without Tipping?

    Homework Statement The forklift and operator have a combined weight of 50,000 N and center of mass at G. If the forklift is used to lift the 10,000 N concrete pipe, determine the maximum vertical acceleration it can give to the pipe so that it does not tip forward on its front wheels...
  37. H

    Rotational kinetics of a rigid body

    Hi, I had a question about a dynamics problem involving the rotation of a rigid body. Here's what I've worked out so far, but I can't seem to get the correct answer. I'm suppose to find the magnitude of the reactionary forces at pin A. See the fbd for a drawing of the problem. I'm not sure if...
  38. A

    Rigid Body Kinetics Homework Help - Solving Equations & Finding Answer

    Homework Statement Homework Equations \SigmaM = I\alpha \SigmaF = ma The Attempt at a Solution I have made an attempt at this problem, it can be seen in the image below. I think I have done everything correctly, but my answer is incorrect. Any help would be greatly appreciated.
  39. U

    Relativistic Kinetics: Finding Neutral Pion Speed, Momentum, Energy

    Homework Statement A rho meson of rest mass 768 MeV/c^2 and total energy of 960 MeV decays into 2 pions, neutral and positive with rest masses 135 and 139.6 MeV/c^2 respectively. Show that the neutral pion has a speed of 0.93588c with respect to the centre of mass frame and that it's momentum...
  40. J

    Calculating Vertical Jump Kinetics

    I'm working on a problem that analyzes vertical jump kinetics. I have a data file that has force plate data and corresponding time steps when a person jumped straight up and then landed on a force plate. I also have the vertical distance that the person jumped. I want to calculate: 1. The...
  41. D

    Kinetics after car left the cliff.

    Homework Statement A car of mass m = 1515 kg is pushed off a cliff of height h = 26 m. If the car lands a distance of 14 m from the base of the cliff, what was the kinetic energy of the car the instant after it left the cliff? Homework Equations The Attempt at a Solution Don't...
  42. C

    Kinetics question in 2 dimensions

    Homework Statement A ball is hit by a golfer. The angle is 28 degrees, the velocity of the projectile is 16.0, the distance is 16.8m on horizontal. What is the velocity before impact on the ground of the ball? Homework Equations The Attempt at a Solution
  43. J

    Maximum Force for Block Stability with Kinetic Friction

    Homework Statement What is the largest force F that can be applied to the large block such that the small block doesn't slide off. There are two blocks of M1=10kg, M2=20kg. M1 is on top of M2, M2 is on top of the table. the coefficients of static and kinetic friction between the two...
  44. S

    How Does Penicillinase Affect Penicillin Kinetics in Staphylococcus Aureus?

    Homework Statement Penicilline is hydrolyzed and thereby rendered inactive by penicillinase , an enzyme present in some resistant bacteria. The mass of this enzyme in staphylococcus aureus is 29.6kd. The amount of penicilline hydrolysed in 1 minute in a 10ml solution containing 10^-9g of...
  45. A

    Smaller Packing Fraction, Higher Nuclear Stability - Chemical Kinetics

    why smaller the packing fraction higher the stability of nucleus ?
  46. G

    Solving First-Order Kinetics for [B] After 7.00 Minutes

    We examine the reaction A B which displays first-order kinetics. We know that k = 0.30 / min. If we begin with [A] = 0.54 M what will [B] be after exactly 7.00 minutes? hey i used the formula In[A]/[Ao]=-kt then rearranged to In[A]=-kt+[InAo] when i sub it in i get...
  47. C

    Partice Kinetics Question - HELP

    Homework Statement As shown in the attachment. At the instant shown the block is moving down the slope. What is the acceleration of the block up the slope if the kinetic coefficient of friction is 0.4? The Attempt at a Solution I'm having problems with two things here, the calculation...
  48. R

    Nuclear Chemistry: Kinetics of Radioactive Decay and Radioactive Dating

    Homework Statement A laboratory rat is exposed to an alpha-radiation source whose activity is 11.3 mCi. What is the activity of the radiation in disintegrations per second? in becquerels? The rat has a mass of 315 grams and is exposed to the radiation for 12.3 seconds, absorbing 39% of...
  49. D

    What is the Force Acting on a Particle with Changing Velocity?

    Homework Statement A 0.2 kg particle moves in the x-y plane under the action of its weight and a force F that varies with time. The velocity of the particle is given by the expression \hat{v} = 7.5(t2 + 3)\hat{i} - (10/3)(t3 - 4)\hat{j} Homework Equations mv1 + \sum\intFdt = mv2...
  50. B

    Kinetics Question (spent over 7 hours on this)

    Homework Statement The following reaction was monitored as a function of time: AB---> A + B A plot of 1/[AB] versus time yields a straight line with slope 5.2×10−2 M \s. If the initial concentration of AB} is 0.210 M, and the reaction mixture initially contains no products, what are the...
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