Chemistry Reaction Rates Overview

Factors Affecting Reaction Rate

• Rate of reaction is influenced by temperature, concentration, surface area, and catalysts.

Temperature and Reaction Rate

• Higher temperatures result in increased particle energy, leading to faster motion and more frequent collisions.

Concentration and Reaction Rate

• Increased concentration of reactants raises particle number in a given volume, causing more collisions per second.

Surface Area and Reaction Rate

• Greater surface area enhances contact between solid particles and reactants in solution, increasing collision frequency.

Catalysts

• Catalysts are substances that accelerate reactions without being consumed, providing alternative pathways with lower activation energy.

Enzymes

• Enzymes are specific biological catalysts effective under particular temperature and pH conditions; extreme conditions can denature them.

Activation Energy

• Activation energy is the minimum energy needed to break initial bonds for a chemical reaction to initiate.

Reaction Definition

• A reaction occurs when particles collide with sufficient energy and proper orientation to break bonds.

Graph Interpretation

• A steep gradient in a reaction rate graph indicates a fast reaction, while a horizontal line signifies that the reaction has ceased.

Rate of Reaction

• Rate of reaction measures how quickly products form from reactants.

Limiting Reagent

• The limiting reagent is the reactant that is used up first, halting the reaction.

Fast Reactions

• Examples of fast reactions include salt dissolving in water and the combustion of magnesium.

Slow Reactions

• Examples of slow reactions are photosynthesis and electrolysis.

Calculating Rate of Reaction

• Rate of reaction can be calculated as the amount of reactant or product divided by time taken.

Balanced Reaction Equation

• The reaction between calcium carbonate and hydrochloric acid is: CaCO3(s) + 2HCl(aq) -> CaCl2(aq) + H2O(l) + CO2(g)

Disappearing Cross Experiment

• Investigating temperature effects involves measuring hydrochloric acid and sodium thiosulphate, heating to a target temperature, and timing the disappearance of a marked 'X'.

Rate Calculation

• Rate can also be calculated as the inverse of time taken (1/time).

Temperature Conversion

• To convert Celsius to Kelvin, add 273.

Exponential Relationship

• An exponential relationship indicates that reaction rate significantly increases with temperature.

Temperature Impact on Rate

• Increased temperature accelerates particle movement, enhancing collision frequency, orientation, and activation energy availability, leading to more successful collisions.

Recovering Solid Catalysts

• Solid catalysts can be recovered through filtration, where they remain on the filter paper as insoluble solids.

Best Catalyst for Hydrogen Peroxide

• Manganese dioxide serves as the most effective catalyst for decomposing hydrogen peroxide.

Decomposition of Hydrogen Peroxide Equation

• The symbolic equation is: 2H2O2 --(MnO2)--> 2H2O + O2.

Industrial Importance of Catalysts

• Catalysts are vital in industry to reduce costs by lowering the high activation energy required for many reactions.