Reactions and Rates

http://socratic.org/questions/what-does-a-potential-energy-diagram-tell-you-about-a-reaction

A reaction coordinate is a graph that is used to measure the progress of a reaction as reactants are transformed into products. In order for a reaction to take place enough energy must be present in the system overcome the activation energy. The state between products and reactants is called the transition state or activation complex, this is where bonds are being formed and broken. The difference between the locations of product and reactants on the graph show delta H positive if products are above reactants negative if products are below reactants. A particle diagram follows the same concept just with particles. Particles must be properly oriented with the reactants facing each and enough energy must be present for the particles to break bonds of existing compounds to form the new bonds of the product.

Simple compounds are more likely to react then complex molecules. Smaller particles will more likely react then larger particles with higher rates as they move at faster speeds creating more chances to collide. Increasing the molarity of a substance or amount will increase chances and rates of reaction as their is a higher amount of reactants to collide with each other. Increasing temperature increases reaction rate and probability of reacting as particles move at an accelerated rate causing more collisions. Adding a catalyst increases reaction rate and and probability of happening as it lowers activation energy for a reaction allowing reactions to occur at lower energies. Decreasing temperature, molarity or amount or reactants, or increasing particle size will lead to slower and less likely reactions.

In the lab Iron(3) nitrate was mixed with potassium thiocyanide to create a the substance below in a chemical reaction.  The diagram would look like this:

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Three Questions 

1. What have you completed recently?

I have taken a test in chemistry, read about world war 1, and played new orchestra music. 

2. What have you learned recently? 

I learned about molecular geometry in chemistry and about the stock market in government.

3. What are you struggling with and planning to do about it? 

I’m still struggling with the molecular shapes and angle degrees. I plan to help this by spending time to memorize the shapes and angle degrees.

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Solid bonds & Properties

There are four types of solids:

1. Metallic: composed of only metal atoms and held together by metallic bonds. Electrons in metallic solids are delocalized, meaning that electrons move freely from atom to atom expanding the molecular oribitals across the whole solid. This is also called a sea of electrons. Since the electrons are delocalized metal nuclei can easily be moved as it does not take much energy to separate atoms. This is what makes metals malleable and ductile. The delocalization of electrons also makes metals excellent conductors. Metallic solids have a wide range of melting points.

2. Ionic: formed from a cation(metal atom) and anion(non-metal atom) bond interactions. Electrons are not delocalized like metallic solids instead they are localized around the anion. Ionic solids are not conductive in solid form but conduct a current in aqueous ion forms. Ionic solids have high melting points the higher the charge of the cation and anion the higher the melting point. Ionic solids are also brittle. Most ionic solids are soluble in water.

3. Network covalent: formed from the covalent bonding of the same atom/atoms throughout the solid. Network covalent solids are hard and have high melting points. Network covalent solids are not conductive.

4. Molecular (Vander walls solids): solids held together by dipole-dipole interactions. hydrogen bonding, and london dispersion forces. This is mostly done by liquids or gases at room temperature when they hit a low temperature forming solids. These solids have low melting points and are soft due to weak bond interactions. Most molecular solids are not soluble in water. Molecular solids are not conductive.

In the lab the properties used to classify the solids were melting point, conductive in solid form and in water solution, and soluble in water polar organic and non-polar organic solutions.

Based on these properties metallic will conduct and ionic, network covalent, and molecular solids will not conduct. Metallic solids will have varying melting points Ionic and network solids will have a high boiling point, and molecular will have low boiling points.

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These are the results(Zinc is conductive as solid):

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Citric acid: molecular CaCl2: ionic  Sand:Network covalent Charcoal: network covalent

Zinc: metallic

sources:

http://ch301.cm.utexas.edu/section2.php?target=imfs/solids/metallic-solids.html

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Three Questions

Recently I’ve read up on the gilded and progressive ages in America. In chemistry I started to construct geometrical shapes of covalent bonds
I’ve learned all about the formations of covalent bonds and how to draw their Lewis dot structures.
I’m am still a little confused about polarity of molecules and where electrons will be concentrated. I will try to better my understanding by reviewing the notes again and completing the phet sims.

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Soap and Pepper Repulsion and Intermolecular Forces

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Intermolecular forces are responsible for the solubility, viscosity, and phase changes of substances.

London Dispersion IMF’s are exerted by any atom or molecule with electrons, this attraction pushes electrons to one side of an atom creating a temporary dipole.

Dipole-dipole IMF’s is where the positive end of an atom or molecule lines up with the negative end of another atom or molecule, forming a permanent dipole.

Hydrogen bonding is formed when hydrogen forms with highly electronegative atoms which are Nitrogen, Oxygen, and Fluorine.

Forces are listed in order of increasing IMF strength.

Water experiences two IMF’s hydrogen bonding and London dispersion (as it contains electrons). Water is polar as electrons are unevenly distributed through the molecule mostly being concentrated around the the oxygen.

Soap experiences London dispersion forces, and soap also contains a non-polar end and a polar end. The polar ends are hydrophilic(attracted to water) while the non-polar ends are hydrophobic(not attracted to water). The polar ends of soap are attracted to each other while the non-polar ends face out and that’s how bubbles are formed.

So why does pepper repel as soon as soap is added to the water pepper mixture. First off soap does not repel pepper. The pepper floats on top of water due to surface tension. Surface tension in water is high due to strong IMF’s with two hydrogen bonds per molecule of water. When soap is added to the water it breaks this surface tension of water causing the water molecules to pull away from the center taking the pepper with it. This is like if you were in a tug-of-war contest and your opponent lets go of the rope you pull away from this person. This is the same idea with the water and pepper. This experiment will also work with any material that will float on top of water not breaking the surface tension.

http://socratic.org/questions/which-liquid-water-or-alcohol-has-stronger-intermolecular-forces

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Sources: http://drholly.typepad.com/ask_me_a_chemistry_questi/2006/01/pepper_and_soap.html

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Three Questions

1. What tasks have you completed recently? 

I have joined symphony, I finished a lab in chemistry, and wrote a analysis of Hamlet’s soliloquy To be or not to be.
2. What have you learned recently?

I have learned lots about light in chemistry, the second industrial revolution is history, and Harry potter on the violin.
3. What are you struggling with &, therefore, plan to do next?

I still struggle with the units in energy equations and lab based quiz questions. I plan to go in for help and correct my quizzes and test to gain a better understanding.

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Coulomb

Coulomb’s law talks about the conditions an electron faces as it leaves an atom, and it has three main points. 1. Coulomb’s law states that protons have a positive charge and electrons have a negative charge. This means that there is a force of attraction between both the particles. 2. Distance is indirectly related to the attractive force between particles. Which means the farther away electrons are from the protons in the nucleus the smaller the attractive force between the particles. 3.Charge is directly related to force. Meaning that the greater the number or size of particles the greater the force of attraction.

http://web.suffieldacademy.org/~vkrasemann/Physics/coulomb.htm

Removing electrons from atoms is an endothermic process as it takes energy to overcome the force of attraction of protons and leave the atom completely. It is not exothermic because this would mean a loss of energy and it takes energy to break bonds.

The organization of electrons can cause the amounts of energy needed for an electron to be removed from an atom to differ. Electrons found between protons and the escaping electron act as a shield to the attractive force asserted by the protons by a 1:1 ratio. For example there is 3 protons and to electrons between the protons and the escaping electron. Only one proton is exerting an attractive force upon the escaping electron.

The excitation of an electron is different from the removal of an electron. Exciting an electron means that energy is added to an electron and it jumps to a higher energy level. Removing an electron means that energy is added to an electron and it completely leaves an atom with no transitions to any energy level within the atom’s orbitals.

Coulomb’s equation brings all these ideas together and calculates force(energy) needed to leave an atom. Coulomb’s Equation is Force is equal to a constant multiplied to charges one and two divided by distance squared.

F=(K)[(q1)(q2)/D^2]

http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/don_bahls/coulombs_law.html

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