1.9 Rate Equations

• The rate equation tells us that only the tertiary halogen or alkene or halo alkane can actually appear in the rate determining step.
• The rate mechanism can also be found for the rate determining step.
• The rate determining step in a chemical reaction is the step that accounts for all the molecules in the rate equation.
• The Arrhenius equation links the activation energy and temperature to the rate constant, which is denoted as K.
• The videos contain information on how to measure a rate of reaction using equipment and plotting graphs.
• The order with respect to B is difficult to determine as a changes in each experiment.
• The rate equation for this reaction can be found using the data from the experiment.
• The order with respect to a is second order, as evidenced by the initial rate increasing by a factor of nine when the concentration of a increases by a factor of three.
• A reaction occurs between a and B, and the experiment was repeated three times varying the concentrations of a and B.
• B is first order with respect to a, as evidenced by the difference between the theoretical and actual values being about half.
• B must have an impact on rate, as the theoretical value and the actual value are different.
• The rate would be quadruple if a is doubled, indicating a second-order reaction with respect to a.
• First order reaction: changes in concentration affect the rate of reaction proportionally.
• The rate constant is temperature dependent and increases when the temperature increases.
• Second order reaction: changes in concentration have a squared proportional effect on the rate of reaction.
• Zero order reaction: if the concentration of a substance is changed, the rate of the reaction does not change.
• The rate constant, denoted as K, is a number that allows us to equate rate and concentration together.
• The rate can be found from the gradients of a graph.
• A rate determining step is the slowest step in a multi-step reaction, and speeding up this slowest step has the greatest impact on the overall rate of the reaction.
• In a multi-step reaction, the total time it takes to make the product can be longer than the time it takes for the slowest step.
• Concentration doesn't change the rate of reaction, so this is a zero order reaction.
• If the slowest step in a multi-step reaction can be identified, it can be speeded up to dramatically speed up the rate of reaction.
• In chemistry, various methods can be used to speed up the rate determining step and hence the overall rate of the reaction, such as using a catalyst or heating up the reaction.
• A zero order reaction shows a straight diagonal line on a concentration over time graph.
• A second-order reaction changes the rate unequally at different concentrations, so the rate concentration graph shows a curved line.
• A first-order reaction changes the rate equally at all concentrations, so the rate concentration graph shows a straight line.
• The gradient of the Arrhenius plot represents EA over R.
• The Arrhenius plot can be used to find the activation energy and the arena's constants.
• The activation energy can be calculated using the Arrhenius equation by substituting in the numbers, for example, EA equals 110 thousand seven hundred eighty-one joules per mole or 111 kilojoules per mole.
• Activation energy increases the rate of reaction because it means there are more particles able to collide with sufficient energy.
• The simplified equation for the Arrhenius plot is ln k equals Ln a minus EA over RT.
• The rate constant K increases as the temperature increases because the particles have more kinetic energy and are more likely to collide.
• The activation energy can be calculated using the Arrhenius equation as EA equals Ln a minus Ln K, where Ln a and Ln K are the natural logs of the activation energy and the rate constant respectively.
• The Arrhenius equation can be used to calculate the activation energy or the rate constant.
• The bigger the section of the graph used to work out the gradient, the more accurate the results are likely to be.
• The gradient of a curve can be found by extending a tangent line across the graph and using the gradient of the line to calculate the rate of reaction at a specific point on the curve.
• Orders of reaction can be zero, first order, or second order.
• The rate equation is represented as rate equals K, the rate constant, times the concentration of B, which depends on the reactants and the reaction.
• Orders in a rate equation are the power to which the concentration is raised to, indicating how the concentration of the substance affects the rate.
• The units of the gradient can be found by taking the units from the x-axis and the y-axis and writing them together.