CHEMISTRY COMMUNITY

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You can tell what half reactions to use by looking at the cell diagram - anode (oxidation) on the left side || cathode (reduction) on the right side. For example, part A: Pt(s)|H2(g)|HCl(aq)||HCL(aq)|H2(g)|Pt. From looking at this cell diagram, we can see that both sides of the cell diagram involve ...

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Activation energy is the minimum amount of energy required for a reaction to occur. Free energy of activation is the difference in free energy (deltaG) between reactants and products.

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Okay, so the ratio they're referring to is Q. This produces a positive cell potential, E, when plugged into the Nernst equation. If you were to plug this value into deltaG = -nFE, it would produce a negative deltaG value (i.e., spontaneous/favorable, and capable of doing work). First, we find cell p...

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The question reads as follows: Write the half reactions, balanced equation, and cell diagram. D. Au+(s) ----> Au(s) + Au3+(aq) The solution manual writes the cell as follows: Au | Au3+ || Au+| Au+. I'm confused as to why we are allowed to use Au for each electrode, even though only one of the redox ...

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The question reads: Write the half reactions and balanced equation for the following galvanic cell: D. Pt(s) | O2(g) | H+(aq) || OH-(aq) | O2(g) | Pt(s) I don't understand how one is able to tell which is oxidation and which one is reduction here - I understand the concept generally, but not in appl...

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When writing a rate law, you do not include liquid or solid reactants, or water, if it is a solvent and not a reactant. As for any other molecule that is not the solvent, if it is part of a reaction, it can be in the rate law.

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My TA said today that whatever we need to complete calculations will be given to us on the equations and constant sheet, so no need to stress!

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Molecularity refers to the number of molecules that come together to react in an elementary reaction, and is equal to the sum of the coefficients of this elementary reaction. So, if you're talking about an elementary reaction, yes!

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It depends on whether the gas in the equation you're working with is under constant pressure (Cp) or constant volume (Cv).

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We have to multiply the specific heat by either 5/2 or 3/2 because these values allow us to calculate the heat capacities of different types of gases. The molar heat capacity of a monatomic gas at a constant volume is (3/2)R, whereas the molar heat capacity of a linear molecule of a gas is (5/2)R. P...

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Assuming this is for the 7th edition here. For anyone who's also having difficulty with this problem and doesn't have the book around, the problem reads: A. Calculate the heat that must be supplied to a copper kettle of mass 400.00 g containing 300.00 g water to raise its temperature from 20C to 100...

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Yep, that's the main difference! ∆H°, enthalpy of reaction, is the ∆H of the system when all products and reactants are in their standard states. ∆H°f, enthalpy of formation, is the ∆H of the formation of 1 mole of whatever compound when all products and reactants are in their standard states.

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Standard reaction enthalpy (∆H°) is the ∆H that accompanies a change in system due to a chemical reaction where all reactants and products are in their standard states. Standard enthalpy of formation (∆H°f) is the ∆H during the formation of 1 mole of the substance, with all substances in the reactio...

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q = ∆H when pressure of a system is constant - this is usually written as qp = ∆H. If pressure is not constant, you could calculate q using q = ∆U - w, presuming you know work or total energy change in the system.

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Yes, it is similar to calculating ∆H of phase changes, because like enthalpy, entropy is also a state function (meaning change is determined by initial and final state, not the path taken). In taking each step and adding them to find total ∆S, we are using Hess's Law; which states that changes are a...

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Simply put, degeneracy is the number of different ways energy can exist, or the different configurations (microstates) a substance can take in a particular state. For example, gases have high degeneracy (the molecules are largely free to bounce around whatever container they're in), whereas solids h...

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If we're talking about expansion of a gas and want to compare the role of temperature in reversible vs irreversible expansions, as we have been in lecture, we could compare these two equations for calculating work: A. w = -nRTln(V1/V2), for isothermal reversible expansion of a gas. B. w = -P∆V, for ...

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Depending on what else is known or unknown in the problem, you could use: A. ∆U = q + w, rearranged as q = ∆U - w, if you know the total change in energy in a system. B. q(p) = ∆H, if you know the total change in enthalpy at a constant pressure. C. ∆S(sys) = -q(rev) / T, if you know the total change...

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Yes, that's usually fine. Another indicator that pressure might be constant is if the problem mentions "standard conditions" - this implies a constant temperature of 273K and a constant pressure of 1 atm.

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Isothermal (temperature of system remains constant, so change in temperature is 0), reversible (can be reversed by an infinitesimally small change in the system). In an isothermal expansion of a gas, pressure falls as the gas expands because temperature remains constant (no extra energy is added to ...

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I don't understand how we know to use "the equivalency of the ideal gas constants" to convert L*atm to joules, or what this really means. Why do we know to use (8.314 K/mol)/(.08206 atm/K*mol) specifically?

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I don't understand when/when not to approximate when doing equilibrium concentration or constant calculations. Is there a way to know before completing all calculations? The textbook says that the value needs to be less than 5%, but I'm not clear as to what needs to be less than 5% or in comparison ...

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How do you find the oxidation number of a metal?

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I don't believe he mentioned in lecture? But I'm sure it would be helpful if naming comes up on the final.

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You might also want to know about buffering in blood - this Khan Academy article explains it well, if you scroll down to "Buffering System of Blood".

https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/a/chemistry-of-buffers-and-buffers-in-blood

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If you're writing the proton transfer equation, you should assume that it refers to removing 1 proton - so your conjugate base would be HSO4-, not just SO4-.

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I don't remember Dr. Lavelle mentioning specific coordination compounds we should know, but memorizing some of the common ligands might be helpful for naming coordination compounds. If you have the 7th edition, Table 9C.1 on page 724 has a list.

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https://chemistry.stackexchange.com/questions/8655/angular-and-radial-nodes

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I found this video helpful for understanding the hybridization of pi bonds.

https://www.khanacademy.org/science/organic-chemistry/gen-chem-review/hybrid-orbitals-jay/v/pi-bonds-and-sp2-hybridized-orbitals

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A good rule of thumb is that if the compound's complex metal ion is not in group 8 or doesn't have a d8 configuration, it's likely tetrahedral.

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Generally speaking, the Schrödinger equation describes wave-particle duality of a particle over time, so yes.

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Yep! As H2SO4 donates a proton, which water accepts, labeling those as acid and base respectively makes sense. Equally, HSO4, is a conjugate base, and hydronium, with its added proton, is the conjugate acid.

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A Bronsted acid is a substance that donates a proton, and a Bronsted base is one that accepts a proton. We can see that HCO3- has a negative charge - it's the conjugate base of carbonic acid, H2CO3.

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I'm also confused by this - I got the same answer, but my TA corrected it as 1.09x10^-7m. Can anyone else who got it correct explain?

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I think the acid's we've had that don't bond normally are oxyacids and acids with multiple protons - I found this hard to explain, so here are a couple articles that do a better job than I can. https://rafamunoa1.wordpress.com/2015/03/19/lewis-structure-of-oxoacids-and-anions-flowchart/ https://web....

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Intramolecular forces are forces that hold atoms together within a molecule - listed strongest to weakest, they include metallic bonds, ionic, and covalent (polar or nonpolar) bonds. Intermolecular forces are forces that exist between molecules - listed strongest to weakest, they include dipole-dipo...

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Double headed arrows usually indicate that a reaction can go either forwards (towards the products) or backwards (towards the reactants).

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Lewis acids and bases are generally defined as electron pair acceptors and donators respectively. When a Lewis acid and base are combined, they form a Lewis adduct (for our purposes here, a single product of two distinct molecules). So, to understand how Lewis acid/bases affect pH: Think of a proton...

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Salts are ionic compounds formed by a neutralization reaction between an acid an a base, such as NaCl, or common table salt. Salts can either raise or lower the pH of a solution - if the salt of a strong base and weak acid is dissolved in water, it will form an alkaline (basic) solution, whereas, th...

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Why do we consider ionization energy over electronegativity when deciding which atom should be the center of a Lewis diagram?

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We cover up until the end of 2C (7th edition), or 3.11 (6th edition). Wednesday's lecture (last day of material that will be on tomorrow's midterm) covered expanded valence shells, radicals, Lewis acids and bases, and coordinate covalent bonds. Lewis acids and bases, broadly speaking, are defined in...

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Why is boron able to provide both electrons when bonding with fluorine, and be satisfied with an incomplete octet?

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You would use the Schrödinger equation to find the allowed energy levels for quantum mechanical systems.

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