CHEMISTRY COMMUNITY

AronCainBayot2K

You may only use aqueous or gas molecules since they have concentrations.

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G is not at standard state G* is at standard conditions.

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There are different units of k due to the powers involved in concentrations. Units could be more than the power of 1 which would change the unit of k.

AronCainBayot2K

Correct, Ka is based on H+ concentration, Kb is based on OH- concentration. You can use these values to determine pH and pOH respectively given the formula.

AronCainBayot2K

I would prioritize Kinetics and also Thermodynamics. The other concepts should all be included, although Kinetics would be could be a main topic.

AronCainBayot2K

You can derive this equation when solving for different temperature phases or k's. Mainly, we would try to find k2/k1.

AronCainBayot2K

Anode should be on the left, cathode should be on the right in most diagrams.

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If activation energy is higher than products, exothermic. If higher than reactants, endothermic.

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n is determined by the amount of electrons transferred in the reactions, easier to find in half-reactions.

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Q should be anode/cathode.

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Graph is linear and slope is usually negative.

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Work done on system is positive, work done by the system is negative.

AronCainBayot2K

You can calculate n whether by the other information given, such as Gibbs Free Energy, or using the half reactions to determine the amount of electrons.

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Use K when reactions are at equilibrium, Q when they are not. Q determines which side of the reaction is favored.

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Kelvin because the ideal gas constant is in terms of Kelvin not celsius.

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Adding an inert gas increases the pressure of the system but in terms of equilibrium it has no effect. Only temperature can do that as it forces the reaction to favor one side or the other.

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Galvanic cells are cells that converts chemical energy into electrical energy.

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Redox in both acidic and basic solutions are very similar. It comes down to adding the H+ or OH- to acidic and basic equations respectively to determine what is being oxidized and reduced.

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T to kelvin should only be applied when the the problem involves using constants or equations that use Kelvin instead of Temperature. In ideal gas law equations, you would use Kelvin (+273.15) if given celcsius.

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Delta G will always be in the conditions given in the problem where as Delta G naught is in standard conditions.

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Cp=DeltaH/Delta T and Cv=DeltaU/Delta T. Calculations can also vary depending on if the atom is monoatomic, linear, etc this is when dealing with Cv,m and Cp,m.

AronCainBayot2K

You can use this when dealing with an isothermal process and also when dealing with phase changes.

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Reversible is when the reaction is at equilibrium where as irreversible is not, an example of this would be combustion. Equations that relate to this would be work in which reversible process would be:-nRTlnV2/V1 and irreversible: -Pex*DeltaV

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Q refers to when the reaction given is not at an equilibrium where as K would mean the reaction is at equilibrium. Usually, Q can = K such that delta g would be 0 and delta g naught would be -RT ln K at equilibrium.

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Phase change occurs when a molecule/reaction goes from solid to liquid, liquid to gas, etc. This denotes fusion, vaporization, in terms of change in enthalpy. We learned equations: Hvap=Hvap-Hliq and Hfus=Hliq-Hsol and Hsub=Hvap-Hsol which relate to phase changes.

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Since it is a state function, enthalpy values can be added together or subtracted.

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The problem should always allow you to find the concentration. If given a change in concentration you can use that to solve for the initial.

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If the number (x) is less than 10^-3

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It usually depends on a lot of factors. If the problem were to give temperature change or volume change nCln (T2/T1) or -nRT ln (V2/V1) respectively. Those are usually the equations you would need to use when there is a change in some constant. Otherwise just know the equations that have work exclus...

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This value usually denotes Cv or Cp. The number depends on if the molecule is monoatomic, diatomic, etc.

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Isolated systems cannot exchange heat or work for that reason delta u will be 0. (0+0=0)

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Gas constant values are dependent on the unit of pressure. Since atm is given, you would use the constant with atm as the units present.

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Conservation of energy, a function of heat and work. Delta U= q+w.

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Pressure, volume, moles, and temperature can all vary as R is is the Ideal gas law constant. Usually, there are relationships such as when volume increases, pressure decreases, while temperature and moles carry a similar relationship.

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Answer should be based on the units given in the problem. Joules can be represented in many units kJ, kg.m^2, s^-2, etc. Just identify what the question asks and have consistent units.

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Only increasing or decreasing temperature can change the value of K.

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The Gas Constant value is determined based on the pressure usually and other components in the ideal gas law equation. Pressure can be measured in atm, bar, etc, and R is represented in many of those units.

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Pure solids and liquids are not included in solving for K. They also cannot dissolve or be used in ICE tables.

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Yes as long as it is in the form of a gas. Any gas or aqueous reactant or product can be included in solving for K.

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R constants are given and should be applied based on the units given in the problem. Pressure is the unit to look for as it determines which R constant to plug ig to PV = nRT

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In an exothermic reaction, the reaction will shift to the left when temperature is increased due to heat already being on the product and needing heat on the reactant side since the reverse reaction is endothermic.

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ICE tables only involve finding the concencentration using only aqueous or gas molecules. Solids or liquids are not included. You also use ICE tables when you are given intial concentrations.

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You can derive the concentration using the ideal gas law. PV=nRT (n/V = P/RT) where n/V gives the concentration.

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An ICE table should be used when given a weak base/acid. When finding concentration always take note of the 5% rule.

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In this reaction, heat is on the product side. This indicates that the reverse reaction is endothermic. In this case, an increase in temperature would favor the reactants, caushing a shift to the left.

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K usually represents Kc or Kp. Kc deals with the concentrations of a reaction whereas Kp deals with partial pressures. I think we would just evaluate the reaction with how we normally calculate for K.

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ICE is used when we are given intial concentrations and we can use gasses from the product and reactant side to solve for x (final concentration).

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For this problem, you would follow the procedure we've been doing K=[P]/[R]. If other temperatures were given, then there would be different K values so just be aware of that. For this problem, the products and reactants are all gasses and so all the concentrations of P and R would be present in the...

AronCainBayot2K

Both can be used for measuring pressure, depending on the context of the problem it would be good to stay consistent with the units.

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Temperature is the only factor than can affect the value of K. Usually when K is given at 2 different temperatures, it is likely that those values would be different due to a difference in energy.

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Kc usually deals with molar concentration and the activity of chemical reactions. Kp deals with partial pressure only when the products and reactants are forms of gasses.

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A molecule would be linear if there is one central atom and no lone pairs on the central atom where as the molecule would be bent if there is a lone pair. The only exception is AX2E3 where it is also linear.

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HI is more stronger because chlorine is more electronegative and will have a stronger bond. The weaker the bond the stronger the acid.

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H20 can be both since it can accept/give protons and it can also be amphoteric.

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Ka values will decrease the more negatively charged the ion becomes. The H+ ion would be harder to lose thus Ka1 would be the greatest.

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Bronsted bases and acids deal with protons (H+) where bases accept protons while acids give them off. Vice versa with Lewis bases and acids except it would be electrons instead of protons.

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CO2 would have a molecular shape of Linear since it follows the AX2 model which corresponds to a bond angle of 180 degrees.

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Elements that can have expanded octets include the 3rd row and every element below. This is due to the d-block with some elements as an exception to this rule. Elements above the third row must fulfill the octet rule when drawing a lewis structure.

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Melting point has a direct relationship with intermolecular forces. If the strength of a intermolecular force is strong, then the melting point must be high and vice versa with a weaker IMF. For example, molecules that have dispersion would have a lower melting point than for example a hydrogen bond...

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Sigma and pi bonds do not really affect molecular shape due to bonds (single, double, or triple) being considered as only one region of electron density.

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Hydrogen bonding occurs when hydrogen is bonded to Nitrogen, Oxygen, or Fluorine. Dispersion occurs when two non polar molecules interact. Also dispersion is the most weakest intermolecular force, while hydrogen bonding is one of the strongest.

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BeCl2 has more covalent character due to the fact that the electronegativity difference is smaller than MgCl2.

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This is due to the lewis structure as carbon monoxide requires a triple bond to fulfill the 10 valence electrons needed in the structure. Furthermore when conducting formal charge, carbon would have a +1 charge while oxygen would have a -1 charge.

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Frequency and velocity are not the same thing as frequency is obtained by dividing the speed of light over a give wavelength where as velocity is always a constant as "c" which is the speed of light.

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Single bonds will always be a sigma bond. Double bonds will always have one pi and one sigma bond. Lastly, triple bonds will always have 2 pi bonds and one sigma bond.

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Electronegativity increases as you go up and to the right of the periodic table thus why Fluorine has the highest electronegativity. Based on electron affinity and ionization energy trends this also correlates with higher electronegativity.

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How do you determine repulsion strength and finding the least amount of repulsion when given a structure?

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How would you determine the angle of a bond and know that it should be lower than a specific type of angle bond? For example, if a molecule is trigonal planar, we would need to know that the bond angles would be exactly 120 degrees?

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What does the term "distort" refer to when talking about naming molecules and angles?

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Electron arrangement refers to the placement of electrons, while the molecular shape would determine the bound atoms of a molecule and show the actual regions of electron density, allowing us to determine the name of the shape of the molecule.

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Since an electron is present, this represents a region of electron density. If it were a bond or lone pair or just a single electron present, as long as there is one electron, it is a region.

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De Broglie Equation is used to find the wavelength of a particle with momentum, usually dealing with an electron. The equation is wavelength (lambda)=h/p where p can be rewritten as mass * velocity, while h represents Planck's constant.

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You only use De Broglie when dealing with a particle with momentum, typically having mass and velocity. When solving for light waves, you would use E=Hv, and c=wavelength*v

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Based on the photoelectric effect, the ejection of electrons are determined by the frequency. If the light source has a short wavelength then it can eject electrons since the frequency would be high.

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The central atom should be the most electronegative and while creating Lewis Structures, you want the formal charge to be as close to 0 as possible. You may need to change/add bonds such as by adding double bonds to fulfill that formal charge, it just depends on the compound given.

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Elements in the third period can have more than 8 electrons and are the only exceptions to the octet rule. For example, Cl would be an exception.

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Formal charge shows us which atom has the highest energy due to it indicating if electrons were gained or lost during the bond. Based on the charge, we would determine which Lewis Structure would be best based on having the lowest formal charges.

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You can tell if a bond is ionic or covalent based on the atoms present. Ionic bonds are bonds between a metal and nonmetal whereas covalent bonds are bonds between two nonmetals. Knowing this, you can determine whether a bond is ionic or covalent.

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When mass is given, use De Broglie hence the "m" in the equation and not on the other light equations. Also the light equations given, usually relate to photons where as De Broglie relates to electrons.

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First, count the amount of valence electrons. Second, determine what atom is most electronegative, this will be the central atom. Next, fill in bonds and dots based on the amount of electrons and the octet rule. Next, calculate the formal charges and keep manipulating bonds until you get the lowest ...

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It just depends on the question and the units given. If V2/V1 was given in mL, and you were to find the other volume using the dilution equation, you would to have your final answer be in mL as well.

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Two contributions to the resonance structure are shown below for each species. Determine the formal charge on each atom and then, if possible, identify the Lewis structure of lower energy for each species. a) Shows two structures of (HS03)^- one with a double bond one without no double bond. b) Show...

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In most cases, double bond placement does not really matter as long as you fulfill the amount of electrons required to represent the molecule and that you follow the octet rule. If you see Hydrogen, Oxygen, Nitrogen, or Carbon, just note that Hydrogen prefers 1 bond, Oxygen (2), Nitrogen (3), and Ca...

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If we were to be given a compound such as ONF, how would we know which atom would be in the middle of the structure?

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Furthermore to Copper and Chromium being the only exceptions, half full/ full d sub-shells have lower energy thus they are more stable. With Cr and Cu having 1 electron on the 4s sub-shell that electron would be willing to be moved to the d sub shell to fulfill that stability.

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Ionic Bonds is when an ion with a positive charge bonds with an ion with a negative charge. This is when a metal typically bonds with a non metal. On the other hand, Covalent Bonds is when two nonmetals form a bond through the sharing of electrons.

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DeBroglie Equation is used to calculate DeBroglie Wavelength. You use this when given given that a particle has momentum and are trying to find the wavelength. To find this number you must use Planck's constant and divide that by the mass and velocity of the particle. Since we are calculating wavele...

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Protons and neutrons have nearly the same mass. How different are their wavelengths? Calculate the wavelength of each particle when traveling at 2.75 * 10^5 m*s^-1 in a particle accelerator and report the difference as a percentage of the wavelength of the neutron. I am confused on how to calculate ...

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Hund's Rule and Pauli Exclusion Principle share a relationship in which both relate to the building-up principle. Hund's Rule states that electrons in same subshell disperse through different orbitals with the same spins (parallel), where as Pauli Exclusion Principle allows a maximum of two electron...

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It would be beneficial if you at least had a general understanding of the electromagnetic spectrum, particular visible light (400-700 nm). There was a question on the textbook, (1A5) I believe where it asks to put some of the radiation in the order of increasing energy, so that may be something to n...

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Yes, protons, neutrons, and electrons all have wavelike properties. Based on De Broglie's Equation, any moving particle with moment has wavelike properties, thus neutrons and protons would fit this property.

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You use M1V1=M2V2 in dilution problems, typically asking for either the concentration or volume in either the initial side or final side of the equation. One to thing to note is to look closely at what the question is asking for. Just because you are given 2 volume measurements and 1 concentration v...

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To convert from angstrom to any other units you must first understand the scientific notation of each measurement. Knowing that information you should use dimensional analysis, in other words, you would be making conversions in which you are cancelling out terms to where the units you want are in th...

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You want your answer to be as accurate as possible so definitely focus on significant figures at the end of your calculation. In most cases, you could get away with rounding Oxygen's atomic mass to 16 grams or Hydrogen to 1.01 grams, but essentially you want to keep those significant figures and rou...

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Based on quantum mechanics, all matter has wavelike properties, including neutrons. As long as there is no indication that the the velocity or mass of an object is 0, it can be inferred that a particle has wavelike properties. We are only able to identify this if a particle has a relative low mass w...

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The difference between the photoelectric effect and atomic spectroscopy is that one focuses on the analysis of light being either emitted or absorbed by a substance (spectroscopy) where as the other focuses on the emission of electrons when light hits a substance, for example metal. In spectroscopy,...

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I would use scientific notation when you have an answer that is either very large or very small, involving a lot of zeros as place holders for instance. You want to make sure your answer looks simplified. For example, even Avogadro's constant number is in scientific notation since the number itself ...

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You should always convert after you've completed all steps necessary. For example if it is asking for volume, evidently the answer should be in some form of liter measurement. In these types of cases, just pay attention to the units given and determine whether you would need it to be in milliliters,...

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Usually, you would need to identify the least amount of significant figures given in the problem. Your answer should reflect that number. One example, could be multiplying the values (17.2) and (2.9) after calculations you would get 49.88 but as you can see, (2.9) has 2 significant figures thus your...

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M19) A stimulant in coffee and tea is caffeine, a substance of molar mass 194 g*mol^-1. When 0.376 g of caffeine was burned, 0.682 g of carbon dioxide, 0.174 g of water, and 0.110 g of nitrogen were formed. Determine the empirical and molecular formulas of caffeine, and write the equation for its co...

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