Instantaneous Reaction Rate
Instantaneous Reaction Rate - Related Videos
02:53
Reaction Rate
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2020
The rate of reaction is the change in the amount of a reactant or product per unit time. Reaction rates are therefore determined by measuring the time dependence of some property that can be related to reactant or product amounts. Rates of reactions that consume or produce gaseous substances, for example, are conveniently determined by measuring changes in volume or pressure. The mathematical representation of the change in the concentration of reactants and products, over time, is the rate...
03:09
Measuring Reaction Rates
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2020
Polarimetry finds application in chemical kinetics to measure the concentration and reaction kinetics of optically active substances during a chemical reaction. Optically active substances have the capability of rotating the plane of polarization of linearly polarized light passing through them—a feature called optical rotation. Optical activity is attributed to the molecular structure of substances. Normal monochromatic light is unpolarized and possesses oscillations of the electrical field in...
10:49
Determining Rate Laws and the Order of Reaction
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2023
Source: Laboratory of Dr. Neal Abrams — SUNY College of Environmental Science and Forestry All chemical reactions have a specific rate defining the progress of reactants going to products. This rate can be influenced by temperature, concentration, and the physical properties of the reactants. The rate also includes the intermediates and transition states that are formed but are neither the reactant nor the product. The rate law defines the role of each reactant in a reaction and can be used to...
02:55
Temperature Dependence on Reaction Rate
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2020
The Collision Theory Atoms, molecules, or ions must collide before they can react with each other. Atoms must be close together to form chemical bonds. This premise is the basis for a theory that explains many observations regarding chemical kinetics, including factors affecting reaction rates. The collision theory is based on the postulates that (i) the reaction rate is proportional to the rate of reactant collisions, (ii) the reacting species collide in an orientation allowing contact between...
02:33
Rate Law and Reaction Order
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2025
The rate of a reaction is affected by the concentrations of reactants. Rate laws (differential rate laws) or rate equations are mathematical expressions describing the relationship between the rate of a chemical reaction and the concentration of its reactants. For example, in a generic reaction aA + bB ⟶ products, where a and b are stoichiometric coefficients, the rate law can be written as: rate = k[A]m[B]n [A] and [B] represent the molar concentrations of reactants, and k is the rate...
FAQs
A tangent is required because a reaction’s speed can change during the observed interval. An average rate uses the slope between two time points and blends behavior across that span, whereas the tangent isolates the local trend at one composition and time. This distinction lets kinetic measurements track changing reaction behavior rather than only overall progress.
Stoichiometric coefficients provide conversion factors between species rates. A product may appear to form faster numerically than a reactant disappears when their coefficients differ, even though both describe the same reaction progress. Dividing each species’ concentration change by its coefficient places the measured rates on a common basis for comparison.
As reactants are consumed, instantaneous reaction rate can change rather than remain fixed. Plotting concentration against time and examining tangent slopes at successive points reveals whether the process is speeding up or slowing down. The resulting pattern connects the measured concentration changes with the reaction’s evolving kinetic behavior.
To obtain a value from experimental data, identify the chosen time on a concentration-versus-time plot, draw or determine the tangent there, and calculate its slope from the concentration and time coordinates used for that tangent. Apply the appropriate stoichiometric coefficient when reporting a reaction rate instead of a single-species rate.
Measurements at specific times show how rate responds to concentration as a reaction proceeds. Comparing these rates with corresponding concentrations supports determination of a rate law and reaction orders, which describe the concentration dependence of the reaction. This analysis turns time-course observations into a quantitative kinetic model.
Because it evaluates speed at a defined stage of reaction progress, Instantaneous Reaction Rate supports comparisons of concentration, temperature, and catalyst effects. Using comparable points or conditions helps show how each factor changes reaction kinetics, while avoiding the loss of detail that would occur if only total time or overall concentration change were considered.