CHEMISTRY COMMUNITY

Kayla Maldonado 1C

The anode goes on the top and the cathode goes on the bottom.The anode is thought to be the diluted concentration and the cathode is concentrated. As the reaction progresses, the concentration will increase in the left (oxidation) anode as the solid electrode dissolves, while the concentration in th...

Kayla Maldonado 1C

Pt (s) is necessary when there is no other solids in the half reactions.

Kayla Maldonado 1C

Abby Soriano 1J wrote:The problem will most likely specify which of the steps is the slow step. You will probably be asked if a proposed mechanism matches the observed rate law, but you won't need to actually calculate a value for the slow step.

If the rate matches the observed rate law is that the slowest step?

Kayla Maldonado 1C

A zero order reaction can simply be when a material such as the surface or catalyst are saturated by the reactants so no a catalyst isn't necessary to make a reaction zero order. In this type of reaction, the limiting factor is something besides concentration which can possibly be a catalyst, but th...

Kayla Maldonado 1C

You can use pseudo first order when trying to find out how the reaction is dependent on only one reactant. This is done by assuming the other concentrations are very large and do not change, so only our molecule of concern is studied. If we have two reactants and we test each one individually by ma...

Kayla Maldonado 1C

How do we solve for E_a in the Arrhenius equation or is it always given?

Kayla Maldonado 1C

The most negatively reduced standard cell potential occurs at the cathode and the most positive standard cell potential occurs at the anode.

Kayla Maldonado 1C

What is the main difference between a concentration cell and a galvanic cell in a cell diagram?

Kayla Maldonado 1C

705302428 wrote:you use it to find the equilibrium constant K. It defines the relationship between activation energy, the equilibrium constant, temperature, and A which is the frequency factor.

How do we get A or the frequency factor?

Kayla Maldonado 1C

Q is the reaction quotient, [Products]/[Reactants] for concentration cells the lower concentration is the products. Or the cathode concentration is the reactants and the anode concentration is the products. Why is the cathode concentration the reactant if the the cell diagram shows it in the order ...

Kayla Maldonado 1C

Please explain what specific aspect of this problem that is making you stuck. The reaction is given as I 2 (g) --> 2 I (g) but on the graph is shows that I is the reactant and I 2 is the product. Is this because the reactants are favored at equilibrium in the given reaction? Or can we depict either...

Kayla Maldonado 1C

Depict the progress of the reaction graphically (as in Fig. 5G.1) for the reaction:
I₂(g) --> 2 I(g)
The graph below is the solution shown in the book can someone explain why I is shown as the reaction and I₂ as the product if the reaction shows it the other way.

Kayla Maldonado 1C

VPatankar_2L wrote:Since one Faraday is 96485 C/mol, it can be multiplied by n (moles) in the equation delta G = -nFE to just get kJ.

What are the units for E and how do we get to Joules from coulombs?

Kayla Maldonado 1C

Kavya Immadi 3D wrote:Without a salt bridge, the cell would stop working soon because the cathode would be too negative and would repulse the electrons which would stop working.

If this were to occur, would the cathode begin releasing electrons back to the anode since it repulses the electrons?

Kayla Maldonado 1C

Standard Cell Potentials can also be negative, but it's more likely to encounter positive standard cell potentials because this means the galvanic cell is favorable and can do work spontaneously without any outside power source such as a regular battery meanwhile a negative standard cell potential w...

Kayla Maldonado 1C

n is the moles of electrons transferred where transfer is the number of electrons going from the oxidized species to the reduced. To find this, we must balance the half reactions and then balance the half reactions against one another so that the number of electrons is equal to each other in order t...

Kayla Maldonado 1C

This also applies for ∆G. ∆G° is simply free energy measured under standard conditions at 1 atm and 25°C and ∆G is the free energy measured under a different pressure and temperature which must be calculated for a reaction.

Kayla Maldonado 1C

Balance each of the following skeletal equations by using oxidation and reduction half-reactions. All the reactions take place in basic solution. Identify the oxidizing agent and reducing agent in each reaction. b). Reaction of bromine with itself (disproportionation) in aqueous solution: Br 2 (l) -...

Kayla Maldonado 1C

We can see galvanic cells in non-rechargeable batteries where there is a spontaneous redox reaction in the flow of electrical charges and electrons flow from the anode (negative since electrons are built up here) to the cathode (positive since it is gaining electrons).

Kayla Maldonado 1C

In this course should we always assume a more positive standard reduction meaning the reaction is more likely to undergo reduction and be on the cathode side (will lead to a positive voltage) ? If not how can we find out if the reaction will be on the anode side vs the cathode side?

Kayla Maldonado 1C

When calculating the equation for overall cell potential you do not need to change the sign of E naught for the reverse reaction.

Kayla Maldonado 1C

When is it necessary to use Pt(s) in the skeletal equation of a redox reaction? In the example that Dr. Lavelle gave in class: 2Fe3+(aq) + Cu(s) -> Cu2+(aq) + 2Fe2+ although platinum is part of the redox reaction, platinum is an inert conductor that is transferring e-, as there is no conducting sol...

Kayla Maldonado 1C

"n" means moles of electrons and can easily be found by looking at your balanced redox reaction and looking at the number of electrons that were transferred. So this is the number of moles of electrons transferred after the entire redox reaction and not the total of electrons transferred ...

Kayla Maldonado 1C

What are the constants in this equation? (example: constant pressure)

Kayla Maldonado 1C

Delta U= q+w and under constant pressure, q_p=delta H and when no work is done Delta U=Delta H

Kayla Maldonado 1C

A negative delta G means that the reaction is spontaneous.

Kayla Maldonado 1C

What is the difference between delta E and delta U?

Kayla Maldonado 1C

Sartaj Bal 1J wrote:The Boltzmann equation is used to represent the relationship between degeneracy, w, and entropy. Degeneracy is the number of ways of achieving a given energy state. The Boltzmann equation also includes the Boltzmann constant which is 1.381*10^-23 J*K^-1.

Can we calculate degeneracy? If so how?

Kayla Maldonado 1C

Usually delta U=q+w but there is not heat (q) exchanged in this problem so delta U= w

Kayla Maldonado 1C

Sometimes it's also easy to think conceptually whether a process can be undone (reversible) or not (irreversible) such as combustion, once something is burned then it cannot be undone, therefore it is an irreversible system.

Kayla Maldonado 1C

The system consists of both kettle + water, and the surroundings supply the heat. Enough supplied heat is needed to raise the temperature of both the vessel and the water because of the idea that heat moves from a hot object to a cold object so both need to be heated because if just the vessel is he...

Kayla Maldonado 1C

She may be referring to the equation
q=n*C*(delta T)
where q is heat transferred, n is # of moles, C is the molar heat capacity, and delta T is change in temperature.

Kayla Maldonado 1C

delta S(surrounding)= -delta H/T
This equation can manipulated to solve for delta H given delta S

Kayla Maldonado 1C

In a closed system, matter does not change, but the energy (heat) can with the surroundings. In an isolated system matter doesn't change and energy cannot change meaning that the system is insulated.

Kayla Maldonado 1C

PranaviKolla2B wrote:Does anyone have any good videos explaining enthalpy and the related equations?

https://www.khanacademy.org/science/che ... v/enthalpy

Kayla Maldonado 1C

Irreversible reactions are reactions in which the reactants convert to products and where the products cannot convert back to the reactants. In reversible reactions, as the reactants react with other reactants to form products, the products are reacting with other products to form reactants. Reversi...

Kayla Maldonado 1C

The joules unit number 101.33 J converts to 1 l atm, one Liter-atmosphere. It is the equal energy value of 1 Liter-atmosphere but in the joules energy unit alternative.

Kayla Maldonado 1C

Kind of like what the previous person said, R is a gas constant, so that can't really be changed (given on our equations sheet). For everything else though, yes there could be change. That's also where the mini-questions during lectures are formed "What would happen to ____ if ____ increased?&...

Kayla Maldonado 1C

Would this be the same for going up a phase? Would it be endothermic in this case since now there is more heat required to break down the phase like a solid to liquid? Yes going up a phase requires energy to be absorbed otherwise defined as an endothermic reaction in order to go from a solid (low e...

Kayla Maldonado 1C

Molar heat capacity is the amount of heat needed to raise the temperature of one mole of a pure substance by one degree Kelvin. Specific heat capacity is the amount of heat necessary to raise the temperature of one gram of a pure substance by one degree Kelvin.

Kayla Maldonado 1C

Endothermic Reactions require heat or absorb it to overcome the activation energy to form products. In an exothermic reaction, heat is released or "exits" the reaction to form the product and no longer can overcome the activation energy in the reverse reaction unless more heat is absorbed.

Kayla Maldonado 1C

Elena Bell 1C wrote:We do reactants minus the products for bond enthalpies because it is broken minus made. The bonds broken require energy, while forming bonds releases energy.

Why is it that in order to break bonds, energy is needed? And to form bonds energy is released?

Kayla Maldonado 1C

Water is a pure liquid and has an activity equal to 1, therefore, it does not affect the equilibrium constant.

Kayla Maldonado 1C

I'm not sure if this answers your question but if the temperature is the same the concentration does not change the equilibrium constant (k). However, if you change the temperature it does change the equilibrium constant. So temperature is the only thing that can affect the the equilibrium constant ?

Kayla Maldonado 1C

How do we know what units to use for the R constant in the Ideal Gas Law?

Kayla Maldonado 1C

Kevin Antony 2B wrote:At low temperatures, most gases are going to act ideally. In this course, we'll probably only deal with ideal gases because this allows for us to apply PV=nRT and infer molecular kinetic energy based on temperature.

How do we know when to apply the ideal gas equation in a problem?

Kayla Maldonado 1C

If you solve K_a or K_b by the approximate method and exceed 5% in order to obtain as accurate an answer as possible, the quadratic method must be used. So I guess, it's just a method of making finding the solution simpler instead of going through the whole quadratic formula if it isn't necessary.

Kayla Maldonado 1C

According to the ideal gas law, PV = nRT, P = nRT/V = concentration (=n/V) * RT. So [partial pressure = concentration * RT]. The way I see it is concentration is moles per liter which means the more moles, the higher the Molarity or Concentration, and as said in the comment above, partial pressure ...

Kayla Maldonado 1C

Le Chatelier's principle can be used to predict the behavior of a system due to changes in pressure, temperature, or concentration. This principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change to reestablish ...

Kayla Maldonado 1C

PV=nRT is the Ideal Gas Law equation. To answer your question, the R is the ideal gas law constant and there are varying corresponding values (for the most part, problems will specify which value to use.) Some examples can include bar or atm. When do we use the ideal gas law equation? How does it r...

Kayla Maldonado 1C

Temperature affects K c because the forward reaction is either exothermic or endothermic. If the forward reaction is endothermic, then the K c value will be larger when the temperature is higher since the forward reaction will absorb the added heat and produce a greater proportion of products to re...

Kayla Maldonado 1C

I agree with Fiona and McKenna! However, I am still confused on the matter of liquids being pure substancews. Can someone clarify how a liquid is different from an aqueous solution and give examples of each? From what I understand, aqueous solutions have a solute and solvent, and liquids do not. Ca...

Kayla Maldonado 1C

Yes an ICE box is only used for gases and aqueous reagents because they are not pure substances and can change over the course of a reaction. In establishing equilibrium constants, solids and liquids are not used/considered due to the fact that they're pure substances that don't change.

Kayla Maldonado 1C

What else besides knowing that the Cl atoms in cisplatin can attach to DNA bases to initiate cell death in chemotherapy is necessary to know about cisplatin?

Kayla Maldonado 1C

Amphoteric molecules usually contain the elements that lie on the diagonal border (metalloids) between the metals and nonmetals where metallic character blends into non-metallic character and the oxides of these elements have both acidic and basic character.

Kayla Maldonado 1C

CHo_3I wrote:
SarahSteffen_LEC4 wrote:On question number 21 of the Marshmallow review. Why does iron have a +2 charge if two of the nitrogens on the porphyrin ligand have a +1 charge?

The two nitrogens actually have a -1 charge, not +1.

How is the charge for the nitrogens -1?

Kayla Maldonado 1C

#16 why is the trigonal planar shape considered nonpolar, how did we determine this ?

Kayla Maldonado 1C

Joanne Kang 3I wrote:min marshmallows 1c... why isn't it neutral?

NH4+ donates a proton and H20 accepts a proton, therefore NH4+is acidic.

Kayla Maldonado 1C

Are London Dispersion forces and Van Der Waals forces the same type of intermolecular force? Why is there always Van Der Waals forces?

Kayla Maldonado 1C

When we name anionic ligands in coordination compounds do we refer to anions that end in -ide as -ido or just -o as a replacement because the book uses -ido and Dr. Lavelle presents both in his LIGAND NAMES IN COORDINATION COMPOUNDS pdf. An example is chloride, when it is named in a coordination com...

Kayla Maldonado 1C

Can we determine the denticity (monodentate, bidentate, polydentate, etc.) of a ligand by simply looking at the coordination compound name? If so, how?

Kayla Maldonado 1C

A strong base is a base that is 100% ionized in solution and if it is less than 100% ionized in solution, it is a weak base. All strong bases are OH– compounds.

Kayla Maldonado 1C

With gases, they occupy more space so the attraction between the molecules are weak. Solids on the other hand are more restricted in their movement, so they have stronger dipole-dipole interactions than gases would. So are all intermolecular bonds between gases generally weaker than those between s...

Kayla Maldonado 1C

Amphoteric refers to the ability to react with an acid or base. An amphiprotic substance is a substance that transfers (accepts or donates) H+ ions.

Kayla Maldonado 1C

All bonds have at least one sigma bond the other bonds are pi bonds.

Kayla Maldonado 1C

I'm confused between the melting point and the boiling point of a compound? Is this referring to the same thing? There is a difference in which the boiling point is the temperature where a material goes from liquid to a gas and melting point is the temperature where a material changes from a solid ...

Kayla Maldonado 1C

My TA sent out an email saying that if you do not have discussion this week both week 9 and 10 homework can be turned in the following week. I'm not sure if it's like this for all TA's.

Kayla Maldonado 1C

A Bronsted acid is an H+ donor (proton donor), and a bronsted base is an H+ acceptor (proton acceptor). In order for a bronsted base to accept an H+ ion, it uses its lone pair of electrons to bind to it. You can then see the connection between a bronsted base and a Lewis base (<- electron pair dono...

Kayla Maldonado 1C

The first coordination sphere is all molecules or ions directly attached the central metal atom shown below.

Kayla Maldonado 1C

A ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. Ligands are Lewis bases due to the availability of a lone pair of electrons that can be donated to create a coordinate covalent bonds.

Kayla Maldonado 1C

A ligand is chelating if it has two or more points of attachment or coordinate covalent bonds to a metal atom or metal ion. When a ligand is chelating a ring structure is formed creating ring-forming groups known as chelating groups.

Kayla Maldonado 1C

Do all molecules have Van Der Waals interactions? What is the order of strongest to weakest interactions ?

Kayla Maldonado 1C

lone pairs count towards molecular geometry not electron domain geometry. so in the case of 4 electron domains (3 bonding and one lone pair), the electron domain geometry would be tetrahedral while the molecular geometry would be trigonal pyramidal. So if asked in a question what shape a certain mo...

Kayla Maldonado 1C

So, the bond angle in H 2 O is 104.5 degrees (from the textbook). On test 2, should we state that the bond angle for all angular molecules is 104.5 degrees or should we just say less than 120 degrees? Angular molecules can have varying bond angles depending on the amount of lone pairs there are suc...

Kayla Maldonado 1C

Polar molecules are asymmetrical in electronegativity and the geometry or formation. Asymmetrical electronegativity meaning there is an atom with a partial positive charge surrounding an atom with a partial negative charge with an electronegativity difference of 0.5-1.6. Asymmetrical formation assur...

Kayla Maldonado 1C

DesireBrown3K wrote:This photo is from the textbook of all the shapes we should know for test 2.

[img]Screenshot%202019-11-16%2017.24.28.png[/img]

The book names what Dr. Lavelle called "bent" as "angular" which is the correct term to use?

Kayla Maldonado 1C

If eV is on the test convert it to joules(on the equation sheet) to ensure you are still in SI units but eV is used to measure energy and can thus measure the energy in a photon.

Kayla Maldonado 1C

A longer bond means a weaker bond as the interaction between the atoms is weaker. Shorter bonds mean a strong pull between the nuclei of the two atoms and thus it requires more energy to break which means it is stronger.

Kayla Maldonado 1C

Any atom with a d orbital has the octet exception. Atoms in row one and two only have the p and s orbitals and thus eight valence electrons, the p orbital has six and the s orbital two. With the addition of a d orbital, atoms are able to accommodate more than eight valence electrons by putting some ...

Kayla Maldonado 1C

Does ionization have the same trend? Ionization energy has the exact same trend. Ionization energy and electronegativity go hand in hand, the more electronegative an atom is the more it wants an electron and thus the more tightly it will hold on to its own electrons. Across a period, atoms gain pro...

Kayla Maldonado 1C

Electronegativity increases in an overall diagonal line starting with Francium as the least electronegative and Fluorine as the most electronegative. This occurs because as you move up a period, the number of valence shells decreases meaning the atom is getting smaller which in turn means the proton...

Kayla Maldonado 1C

How do we know when a molecule has resonance? A molecule has resonance when it has a bond that can be drawn in a different place and not alter the overall formal charge of the atom or molecule itself. For example, if you have a carbon single bonded to two oxygen and single bonded to another, you ca...

Kayla Maldonado 1C

When drawing lewis structures will we be given the electronegativity table to determine which atom will be the central atom?

Kayla Maldonado 1C

How do we know how many valence electrons an element with an expanded octet has? How are lone pairs shown in a lewis dot structure?

Kayla Maldonado 1C

The reference sheet will most likely be like the one given on the first test. It did include these equations, but did not give the name of each equation.

Kayla Maldonado 1C

Arianna Perea 3H wrote:why is the central atom the one with the least electronegativity?

The least electronegative elements are in the center of lewis structures because an atom in the central position shares more of its electrons than does an atom on the sides of the central atom or the terminal position.

Kayla Maldonado 1C

Dipole Moment refers to the momentary positive or negative charge which exists on an atom when the electrons are temporarily located at a given position on it. It is represented by an arrow placed between the partial positive and partial negative charges on two atoms, with the arrow pointing toward...

Kayla Maldonado 1C

The least electronegative elements are in the center of lewis structures because an atom in the central position shares more of its electrons than does a terminal atom such as Hydrogen which is never found in the center.

Kayla Maldonado 1C

When talking about ionization energy, why is it that it's harder to remove a 2nd electron from an atom and does this mean that there are multiple ionization energies for an element?

Kayla Maldonado 1C

How can you tell if a compound has resonance and do all resonance forms need to be drawn when being asked for a lewis dot diagram?

Kayla Maldonado 1C

Both Boron and Aluminum are both satisfied with six valence electrons instead of 8 as implied by the octet rule.

Kayla Maldonado 1C

How do you know whether or not two elements share a covalent or ionic bond and why?

Kayla Maldonado 1C

n represents the principal quantum number which is the shell that the electron is located on. l is the angular momentum quantum number and it describes the shape of the orbital. It can either be an s orbital, p orbital, d orbital, or f orbital. m is the magnetic quantum number and it tells you the ...

Kayla Maldonado 1C

All things have wave-particle duality, but due to the behavior of large objects, they act more as particles than waves. Things that are quantized have behaviors that must consider both the wave properties and particle properties such as electrons.

Kayla Maldonado 1C

I'm still confused as to if Rydberg's formula can work for only for the hydrogen emission spectrum? Why or Why not?

Kayla Maldonado 1C

Due to the fact that orbitals act as waves, a wave function is a mathematical function that shows the wave-like behavior of electron(s) in an atom and the probable location to finding an electron in a specific region around the nucleus of an atom.

Kayla Maldonado 1C

Increasing in energy levels refers to an electron within an atom when they absorb enough energy to move from a lower to higher energy level.

Kayla Maldonado 1C

After determining the wavelength (m) using De Broglie's wave equation use the answer to determine if it's below any # x 10^-15 in scientific notation, if it is then it's considered to have wavelike properties and if it's above that it does not have wavelike properties. The smaller the wavelength, th...

Kayla Maldonado 1C

When an electron gets excited, it absorbs energy and jumps to a higher energy level. An excited electron can release energy in the form of a photon and "fall" to a lower state due to the fact that an excited electron is unstable and rearranges itself to return to its lower energy state.

Kayla Maldonado 1C

In one example given in lecture, we are asked to calculate the De Broglie wavelength of an electron traveling at a specific velocity (m.s^-1) and the question given doesn't include the mass (kg) of an electron. Are we suppose to already know or memorize the mass of an electron or is the information ...

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