CHEMISTRY COMMUNITY

Cade Okohira 4K

Volume is constant in a bomb calorimeter, and usually pressure and temperature change when combustion occurs within the bomb calorimeter. The heat released is thus taken up by the calorimeter.

Cade Okohira 4K

How would you derive the vant Hoff equation from the two Gibbs free energy equations?

Cade Okohira 4K

Are electrolytic cells only unique in that they use non-spontaneous reaction to create chemical energy or is there more differences between them and galvanic cells?

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Catalysts are at the beginning and end of a reaction, and are not shown in the overall reaction, but can they be in the overall rate law?

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In examples in the textbook, dimerization is the fast part of a reaction process. Is dimerization always fast?

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element 1: That was sodium funny!
element 2: I slapped my neon that one!

Cade Okohira 4K

In galvanic cells, the cell potential must be positive for the travel of electrons and for the electric current to travel through the system. If the cell potential is negative, then the electric current won't travel through.

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Hydrolysis is a catabolic reaction, in which large molecules are broken down into smaller ones. Thus, a fair amount of energy is released and the reaction is endergonic.

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I'm wondering what equation or process of steps you would use to find the pH of one of the solutions holding an electrode in a galvanic cell, if you are given the overall cell potential and the molarity of one of the electrodes?

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What kind of fish is made out of sodium?

2 Na

Cade Okohira 4K

Gibbs free energy answers the questions of whether one of the potential driving forces of a chemical reaction are favorable or not. When Gibbs free energy changes from positive to negative, it changes from being not spontaneous to being spontaneous. When it changes from negative to positive, the fre...

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An irreversible process is a process that cannot return both the system and its surroundings to their original conditions. The reason real processes are irreversible because there are many factors that affect these processes, such as friction, unrestrained expansion of a fluid, and a mixing of two d...

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Residual energy is the difference in entropy between a non-equilibrium state and crystal state of a substance close to absolute zero. This uses the Boltzmann equation, which is S=Kb*lnW. Kb is the Boltzmann constant, and W (degeneracy) can be found by finding the number of possible microstates of th...

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The Gibbs Free Energy formula can tell about the spontaneity of a rxn based on just the signs of delta H and delta S. If delta H is positive and delta S is negative, then the rxn is not spontaneous, which makes sense because if the enthalpy is positive, this means that the reaction requires heat and...

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I was also wondering how W(degeneracy) was calculated. What do W1 and W2 mean in terms of calculating absolute entropy?

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When a gas expands reversibly, the external pressure is matched to the pressure of the gas at every stage of the expansion. Thus, the steps that correspond to the increase in volume are infinitesimal, and thus achieve maximum area under the curve. This results in the maximum work.

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Are there any examples of how to calculate empathy changes from calorimetric data?

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I was wondering, how are reversible processes related to isothermal expansion and how it comes into play when calculating the work of isothermal expansion?

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Thermodynamics is the branch of physical science that deals with the relations between heat and other forms of energy. Enthalpy is a thermodynamic quality that means the total heat content of a system and is equal to the internal energy of the system plus the product of pressure and volume.

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What are the three methods for enthalpy calculation in order from least to most accurate?

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You can ignore the "x" or change in acid when Keq is less than 10^-3. However, after you find the equilibrium concentrations, you should check the % ionization or deprotonation of the acid/base. If it is less than 5%, then ignoring the change is valid.

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First, you would need to convert the mol amounts into molarity, or mol/L by dividing the mol amounts by the amount of L, which is 3 L. Then, you can create an ICE table, knowing that 60% of the H2 had converted into product. Then, you can find Kc by calculating [HI]^2/[H2][I2].

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The strength of acids and bases is determined by their Ka and Kb, respectively. So the higher the Ka, the stronger the acid, and the higher the Kb, the stronger the base. However, for pKa and pKb, they work the opposite way: the higher the pKa, the weaker the acid, and the higher the pKb, the weaker...

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You find Q and K in the same way, by dividing the concentrations of the products by the concentrations of the reactants. However, K is the equilibrium constant, while Q is the reaction quotient, which is the constant of the equation at any time. Q can then be compared to K to find out whether the eq...

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In chemical reactions, chemical bonds are either broken or formed. Generally, when chemical bonds are formed, heat is released, and when chemical bonds are broken, heat is absorbed. So, heat prefers endothermic reactions because the system gains heat. Meanwhile, a chemical reaction is exothermic if ...

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I was informed that we should just memorize the strong acids and bases, and there are seven common strong acids and eight strong bases, which can be found here: http://www.austincc.edu/chemlab/strongacidbase. If they are anything other than these acids/bases, then we can assume the acid/base is weak...

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Because K doesn't change when pressure changes, a decreasing volume (or increasing pressure) with more moles of gas on the left will cause the reaction to shift to the right. When the volume is decreased and there are more moles on the right, then the reaction shifts to the left. However, when addin...

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The temperature must remain the same because a change in temperature will cause K, the equilibrium constant to change. If the reaction uses heat while forming the product, then heating will favor product formation, which is an endothermic reaction. If the reaction gives off heat while forming produc...

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When using the quadratic formula to find the "x" that you have created to find the equilibrium composition of a certain reaction, you must omit answers that are negative and those that are larger than the initial reactant concentrations or pressures. The answers cannot be negative because ...

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This correlation also goes along with the amount of bonding occurring: so single bonds are the weakest and longest, while triple bonds are the strongest and shortest.

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Do we need to know electron-deficient compounds, the compounds with too few valence electrons to be assigned a valid Lewis structure? Do we need to know examples or just the definition?

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What would the VSEPR model for a T-shaped structure be? Or could there be variations of the VSEPR model?

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I was wondering does polarity always have to do with the symmetry of the molecule or are there exceptions?

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I was wondering if for resonance structures do you need to have the same element of atom surrounding the central atom? And can there be more than one double bond for resonance to occur?

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When there are 5 bonding regions, the model can be either AX5, AX4E, AX3E2, or AX2E3. For AX5, its molecular geometry is trigonal bipyramidal, with 3 atoms in a plane in equatorial positions and two atoms above and below the plane in axial positions. For AX4E, the lone pair of electrons in the equat...

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First you need to convert the wavelength to energy, which you can do my manipulating the two formulas E=hv and c=v(wavelength) to get E=hc/wavelength. I found this to be 3.375x10^-19 J. For part b, I converted mg into mol and then into atoms. Then, I multiplied this amount by the answer I found in p...

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I said that the photoelectric effect best supports this idea because in this experiment, a certain light was used to try to eject an electron from a metal. Increasing the intensity was thought to increase the energy, but this did not work. Only changing the type of light to a lower wavelength worked...

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The textbook asks this question but I don't understand how to answer it.

How do you account for the large decrease in electron affinity between, for example, lithium and beryllium?

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I believe when filling up an orbital, you must fill all orbitals possible with one electron spin before assigning the opposite spin. If there's just one electron, it would be spin up.

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The De Broglie equation can be used for any object that has rest mass, because it was found that just as light as both wave and particle properties, electrons also have both. So, the De Broglie equation is usually used to when the object's wavelength we are told to find has mass. If we are doing pro...

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We know that the since the wavelength is 102.6 nm, the n(1) must be equal to 1 because it is part of the Lyman series. However, to find the initial value of n, we must use Rydberg's equation. First, we can use v=c/wavelength to find the frequency of the electron: v=(3x10^8 m/s)/(102.6x10^-9 m) = 2.9...

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Hello, I was confused about the second part of this post module problem: 29. In 1.0 s, a 60 W bulb emits 11 J of energy in the form of infrared radiation (heat) of wavelength 1850 nm. What is the energy per photon of light emitted? How many photons of infrared radiation does the lamp generate in 1.0...

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For A, I used the formula for kinetic energy, which is 0.5*(mass of electron)(velocity)^2. The velocity is given, and the mass of an electron is the constant 9.109 x 10^-31 kg. After plugging these two values into the equation, you should get the result 1.989x10^-19 J, which corresponds to D.

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I solved most dilution problems by using the equation Molarity(M)= mol of solute (n) / vol of solution (V). From this equation, we know that when diluting the solution, the moles of solute remain the same. So, n(initial)=n(final), and also M(initial)V(initial)=M(final)V(final). Using this formula, p...

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I first converted the percentages into portions of 100-gram samples. Then, I divided these gram amounts by each individual elements' molar masses to find the amount of moles of each element. Then, I divided these mole amounts by the smallest mole amount. This gave me the ratio of 2.67(C): 2.67(H): 1...

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I believe that you can instead just convert the grams to moles of each reactant/product. Then, you can use the mole ratios of the reactants and products to determine which is the limiting reactant. For example, for the equation CaC2 + 2H2O = Ca(OH)2 + C2H2, the reactants have a mole ratio of 1:2, so...

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