In high school chemistry, we learn that Covalent bonds involve the sharing of one or more pairs of electrons between two atoms. We can represent these bonding pair of electrons in a diagram. The electrons are shown to be midway between the two atoms . For a homonuclear bond (two atoms are the same elements), this is approximately […]
How do we determine the number of neutrons in a given atom? First, let’s define some terms that you’ll need to be familiar with. The atomic number of an atom is the number of protons in the nucleus of that atom. The mass number (also called the nucleon number) of an atom is the total […]
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
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 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 […]
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, […]
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)
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 […]
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 […]
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 […]
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. […]
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 […]
Overview There are two types of rate laws that we need to learn for AP chemistry: (1) Differential rate law (2) Integrated rate law What is the difference between the differential rate law and integrated rate law? The differential rate law is actually a derivative of the integrated rate law. In experiments: Differential rate law […]
Methods for determining order of reaction This section looks at how concentration affects reaction rate. You will learn how to determine the order of a reaction. Reactions are often categorized into first, second, third order, etc. and this information is useful for showing the mathematical relationship between concentrations and rates. Rate laws may be written […]
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 […]
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 […]
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 […]
