B2 Chapter 11 Q Flashcards
(21 cards)
What is titration and what is it used for?
Titration is an analytical technique used to determine the unknown concentration of a solution. It involves gradually adding a solution of known concentration (the titrant) from a burette to a measured volume of another solution (the analyte). When the reaction reaches the equivalence point, a sharp colour change from an indicator shows the end of the reaction.
What is a titrant and how is it used in titration?
A titrant is a solution with a known concentration that is added to a solution with an unknown concentration during titration. It is typically delivered using a burette in small amounts until the reaction reaches completion. The exact volume used helps calculate the concentration of the unknown solution.
What is a titrate in a titration experiment?
The titrate is the substance being analysed in a titration. It is usually the solution of unknown concentration placed in a conical flask. The titrant is added to the titrate until the chemical reaction between them is complete.
Why is an indicator used in titration?
An indicator is used to show when the titration reaction has reached its end point. It changes colour sharply at the equivalence point, which helps identify when the correct volume of titrant has been added. The choice of indicator depends on the pH range of the reaction.
What is colorimetry and how does it work?
Colorimetry is a technique used to measure the concentration of coloured substances in solution. A colorimeter passes light of a specific wavelength through the sample and detects how much is absorbed. The amount of light absorbed is proportional to the concentration, following the Beer-Lambert Law.
How is mass change used to study reaction rates?
Mass change is used to observe the difference in mass during a chemical reaction, usually when a gas is released. A balance records mass at regular intervals, and the rate of mass loss shows how fast the reaction proceeds. It is commonly used in reactions that produce gases, like metal-carbonate reactions.
What is the gas collection method in experiments?
The gas collection method measures the volume of gas produced during a reaction. A gas syringe or inverted measuring cylinder is used to collect the gas over time. This method is useful for tracking rates of gas-generating reactions like metal-acid or decomposition reactions.
What does ‘reaction rate’ mean in Chemistry?
Reaction rate refers to how quickly reactants are used up or products are formed in a chemical reaction. It is usually measured as the change in concentration per unit time, with units like mol dm⁻³ s⁻¹. Factors like temperature, concentration, surface area, and catalysts affect the rate.
What is the initial-rate method and why is it used?
The initial-rate method measures the rate of a reaction at the very beginning, before any concentrations significantly change. It provides data based only on the starting conditions of the reactants. This method helps determine the order of reaction with respect to each reactant.
What is the continuous monitoring method in reaction rate experiments?
The continuous monitoring method involves recording changes like colour, mass, volume, or pH throughout the whole reaction. This gives a full set of data to analyse how the rate changes over time. It allows for plotting graphs such as concentration–time, which can be used to determine reaction order and half-life.
What is a rate equation and what does it show?
A rate equation shows how the rate of a chemical reaction depends on the concentrations of the reactants. It has the form: rate = k[A]^m[B]^n, where k is the rate constant and m, n are the reaction orders. The powers m and n must be determined experimentally.
What does ‘order of reaction’ mean?
Order of reaction refers to the power to which a reactant’s concentration is raised in the rate equation. It tells you how the concentration of that reactant affects the reaction rate. It can be zero, fractional, or even negative, and must be found through experiments.
What is meant by ‘overall order of reaction’?
The overall order is the sum of the individual orders of all reactants in the rate equation. For example, in rate = k[A]^1[B]^2, the overall order is 3. It helps to determine the units of the rate constant and shows how the total concentration affects the rate.
What is the rate constant (k) and what does it depend on?
The rate constant is a proportionality factor in the rate equation that links concentration to the rate of reaction. It stays constant for a given reaction unless the temperature or catalyst is changed. Its units vary depending on the overall order of the reaction.
What is half-life in the context of chemical reactions?
Half-life is the time taken for the concentration of a reactant to decrease to half of its original value. In first-order reactions, the half-life remains constant regardless of the starting concentration. It can be used to calculate the rate constant and analyse reaction kinetics.
What is the rate-determining step in a chemical reaction?
A: The rate-determining step is the slowest step in a multi-step reaction mechanism. It controls the overall rate of the reaction. Only the reactants involved in this step appear in the rate equation. This step acts as a bottleneck for how quickly products form.
How does activation energy affect the rate of a reaction?
Activation energy is the minimum energy particles must have to react. If the activation energy is high, fewer particles will successfully collide and react, so the rate is slower. Lower activation energy means more successful collisions and a faster reaction at the same temperature.
What is a heterogeneous catalyst and how does it work?
A heterogeneous catalyst is in a different phase from the reactants, usually a solid while the reactants are gases or liquids. It provides a surface where reactants adsorb and react more easily. After the reaction, products desorb from the surface, leaving the catalyst unchanged.
What is a homogeneous catalyst and what is its role?
A homogeneous catalyst is in the same phase as the reactants, often dissolved in the same solution. It forms intermediate species during the reaction and is regenerated at the end. This type of catalyst provides an alternative reaction pathway with lower activation energy.
What does a reaction mechanism describe?
A reaction mechanism shows the individual steps through which reactants become products. Each step involves elementary reactions and may include intermediates. The mechanism explains the detailed molecular changes and helps predict the rate law.
What does “with respect” mean in reaction kinetics?
“With respect” refers to how the rate depends on a particular reactant. For example, if a reaction is first order with respect to A, then doubling A’s concentration doubles the rate. It helps focus the discussion on specific components in a reaction.
