Catalyst and Activation Energy

Catalyst A catalyst is a substance that speeds up a chemical reaction but it does not undergo a chemical reaction itself. The catalyst allows the reaction an alternative pathway to take place. The catalyst does not lower the activation energy of the reaction. Analogy

Entropy – Microstate and Macrostate

The term microstate refers to the behavior of atoms and molecules in terms of how energy is redistributed among the particles in a system. A microstate is the arrangement of molecules within a macrostate, that is, within a system with very specific properties. If atoms have more energy and freedom of movement in a macrostate, […]

Bond Energy and Bond Enthalpy

Bond Enthalpy Introduction In order to understand why breaking bonds requires energy (endothermic) and making bonds releases energy (exothermic), one must first understand the nature of a chemical bond and why it occurs in the first place. Remember that bonds are due to the exchange or sharing of electrons between atoms. Forming bonds is a […]

Reaction enthalpies

Enthalpy change For a reaction Bonds Know that Breaking bonds always requires energy (never releases energy) Forming bonds always releases energy (never requires energy) Exothermic and endothermic process Breaking bonds is always an endothermic process (whether breaking single, double or triple bonds). Forming bonds is an exothermic process (whether making single, double or triple bonds). However, […]

Reaction Coordinate Diagram

Given the following reaction, sketch a reaction coordinate graph. The reaction involves two steps, step 1 is the slowest step and step 2 is the fastest step. Indicate on the diagram the overall enthalpy change of the reaction, the reaction for the transitions states and intermediate states.

H2(g) + 2ICl(g) –> 2HCl(g) + I2(g)

Memorizing the Names of Polyatomic Ions

 Examples of polyatomic ions Generally, polyatomic ions have suffixes that end in “ite” or “ate” if they contain oxygen atoms.   chloride hypochlorite chlorite chlorate perchlorate Note: Chloride shown above is not a polyatomic ion, it’s a monoatomic ion consisting of only one atom. Examples of other polyatomic ions: Oxyanions Oxyanions are ions that contain […]

Compounds with Polyatomic Ions

What are polyatomic ions? Ions are formed when neutral atoms gain or lose electrons. Similarly, a polyatomic ion is formed when a neutral molecule gains or loses electrons. A polyatomic ion is a charged group of atoms covalently bonded together. Majority of the polyatomic ions are anions, meaning they are negatively charged. Ammonium is the […]

Naming inorganic compounds

AP CHEMISTRY TEACHERS – WE HAVE RESOURCES FOR YOUR ENTIRE CLASS TO USE… Identify if a compound is covalent or ionic You will need to know the periodic table You must be able to identify the non-metals, metals, and transition elements in the periodic table You must be able to categorize a compound as ionic […]

Learn the rules for ionic compounds

Background: How ionic compounds are formed Ionic compounds are formed from the electrostatic attraction of oppositely charged ions. The ions are arranged in such a way that they form a giant crystal lattice of alternating positive and negative ions. An example of an ionic compound is sodium chloride, NaCl, also commonly known as table salt. […]

Learn the rules for covalent compounds

Covalent compound A covalent compound involves two non-metals forming a chemical structure together.  Rules What are the rules for naming covalent compounds? • Covalent compounds involve multiple non-metals • Covalent compounds use prefixes – to indicate the number of atoms of each element in the compound • The element that further left of the periodic […]

Integrated Rate Laws

Overview The differential rate law relates the change in concentration of a reactant over a specified time. In other words, it tells us about the overall rate of a reaction from the beginning to the end of the reaction and the rate law also tells us how the speed of a reaction is impacted by […]

Rate of reaction

Measuring rate This section aims to cover the following topics: Define chemical reaction rate Define rate expression Relative rates of reaction and stoichiometry ratio Change in concentration over time The rate of a chemical reaction can be thought of as the speed at which a chemical reaction happens and this can be expressed as the […]

Mechanisms and Intermediates

Reaction mechanism Chemical reactions often take place in multiple steps and it’s not always obvious from looking at the chemical equation. For example, the decomposition of ozone: From the equation, it appears that O₃ decomposes to O₂ in one step. In reality, it’s more likely to take place in the following sequence: The above shows […]

Introduction to Chemical Kinetics

Energy Kinetics involves studying what makes chemical reactions happen. Every reaction that happens involves some energy exchange, whether it’s slow reaction such as iron rusting, or a faster reaction, such as when a rocket burns fuel during take off.  Size of particles Pictures in the slider: (CC BY-SA 3.0) | Link: https://en.wikipedia.org/wiki/Dust_explosion | Author: Hans-Peter […]