CHEMISTRY COMMUNITY

Deepika Reddy 1A

No, it depends on the value for the other electrode in the galvanic cell. The standard hydrogen electrode is always 0. If the standard reduction potential of the other electrode is lower than 0, then that will be the oxidation half-reaction and will be on the anode side of the galvanic cell.

Deepika Reddy 1A

When the standard potentials of half-reactions are given, they are given from the reduction standard table. Looking at the two values, choose the smaller value to be the oxidation half-reaction. Since the standard potential is from the reduction table, flip the value so it is the opposite and it mat...

Deepika Reddy 1A

The unique rate law is one that is the same for all the reactants and products in the reaction. It is not unique to each substance, it is for the overall reaction. The differential rate law relates the rate and the concentrations of the reactants. The integrated rate law relates time to the rate.

Deepika Reddy 1A

A catalyst decreases the activation energy of a reaction. The Arrhenius equation includes both the activation energy and the rate constant. It shows that an increase in the activation energy would lead to an increase in the rate constant.

Deepika Reddy 1A

There's not a certain time that is considered the slowest step. It is just that it is slow relative to the other steps in the mechanism. It needs to be the slowest out of all the steps in the mechanism and then it can be called the slowest step or the rate-determining step.

Deepika Reddy 1A

The mass of the electrode does not affect the cell potential. But if the mass of the electrode is larger, the life span of the galvanic cell will be longer. If the mass of the electrode is smaller, then the span of the galvanic cell is shorter.

Deepika Reddy 1A

I believe that the stoichiometric coefficients can be used when we are dealing with reaction mechanisms but can not be used for overall order reactions and finding the overall reaction rate. For overall reaction rates, experimental evidence needs to be used.

Deepika Reddy 1A

You would never have to come up with the reaction mechanism. You would just have to interpret them or see if with the information you have you can prove the reaction mechanism is correct or wrong.

Deepika Reddy 1A

You figure out the overall order by adding together all the exponents in the rate law.

Deepika Reddy 1A

I believe you need to look at the reduction potentials in order to determine this. A reducing agent is stronger than another if it has a lower reduction potential and an oxidizing agent is stronger if it has a higher reduction potential.

Deepika Reddy 1A

If an element is reduced, that means it is the oxidizing agent because it causes something else to be oxidized so it can be reduced. If an element is oxidized, that means it is the reducing agent because it causes something else to be reduced so it can be oxidized.

Deepika Reddy 1A

In order to find how many electrons are lost or gained, split the overall reaction into the two half-reactions. After balancing the atoms on either side of the half-reactions, looking at the charges should tell you where you need to add the electrons in order to balance the charges. After doing this...

Deepika Reddy 1A

To determine half-reactions, you have to look at the oxidation states of the elements on either side of the reaction and determine how they change between the reactants and the products. If the oxidation state of the element increases, then it is being oxidized. If the oxidation state of the element...

Deepika Reddy 1A

Overpotential is additional energy that needs to be added in order to power an electrolytic cell. By decreasing overpotential, we decrease the amount of electrical energy that has to be supplied to the cell in order for the chemical reactions to occur which would make it more efficient.

Deepika Reddy 1A

If cell potential is positive, then Gibbs free energy should be negative and the reaction should be spontaneous. If cell potential is negative, then Gibbs free energy should be positive and the reaction should be nonspontaneous.

Deepika Reddy 1A

The table that gives us all the standard potential values is only the reduction standard potentials. Therefore, the oxidation half-reaction needs to be reversed.

Deepika Reddy 1A

Galvanic and voltaic cells are the same thing. Galvanic cells and electrolytic cells are the ones that are different. They are the opposite of each other. Galvanic cells and voltaic cells are the same things and both convert chemical energy into electrical energy.

Deepika Reddy 1A

If the Gibbs free energy value is positive, then the reaction is not spontaneous and requires energy in order to occur. If the Gibbs free energy value is negative, then the reaction is spontaneous, then the reaction is spontaneous and there is a release of energy. A lower negative value of Gibbs fre...

Deepika Reddy 1A

I believe that it is important because it determines how you balance the redox half-reactions. Depending on whether the solution is acidic or basic, the solution is balanced differently.

Deepika Reddy 1A

Yes, we need the list of standard electrode potentials in order to do the problems. Or we will be given a part of another equation, like the Gibbs free energy part, and we can calculate the energy potential.

Deepika Reddy 1A

A metal will dissolve if it is part of a redox reaction. If the metal is part of the oxidation half-reaction, then it will lose electrons during the reaction and release ions into the solution. This will cause the metal to slowly dissolve away.

Deepika Reddy 1A

I believe this has to do with the fact that unfavorable reactions are not spontaneous and need some input of energy in order to occur. Favorable reactions are spontaneous and release energy. By coupling these reactions, the energy released from the favorable reactions can be used to drive the unfavo...

Deepika Reddy 1A

A salt bridge ensures that the beakers do not have a build-up of charge. If the beakers are allowed to have charge build-up, then the galvanic cell would stop working because the electrons would not transfer to the reduction reaction beaker because of the buildup of negative charge. The salt bridge ...

Deepika Reddy 1A

In a galvanic cell, there are electrons flowing from one beaker (the oxidation reaction) to the second beaker (reduction reaction). This means that there is going to be a building up of negative charge in the reduction reaction and it is gaining electrons and a buildup of positive charge in the oxid...

Deepika Reddy 1A

Basically, there are two beakers and we are looking at a redox reaction taking place. One of the half-reactions is taking place in one of the beakers and the other is taking place in the second beaker. One of the reactions will be an oxidation reaction and will be losing electrons and the other reac...

Deepika Reddy 1A

You can tell this by looking at the pH of the solution or the concentration of hydronium and hydroxide. If the pH is lower than 7, then the solution is acidic. If the pH is higher than 7, then the solution is basic. If the concentration of the hydronium ions is higher than the hydroxide ions, then t...

Deepika Reddy 1A

Two of the answer choices can be crossed out immediately. I crossed out B because C(diamond) is more ordered than C(graphite) so entropy was decreasing because there are fewer states or positions that the particles can assume. In D, the gas and liquid are going to two aqueous so it can be crossed ou...

Deepika Reddy 1A

After looking at both reduction potentials, you reverse the one that has a lower reduction potential. This is because the one with the higher reduction potential is more likely to be reduced than the one with the lower reduction potential. So, therefore, you reverse the one with the lower reduction ...

Deepika Reddy 1A

The first thing I did was I wrote out the reaction that would take place for the acid CH3COOH. When this is added to water, you end up with H30+ and CH3COO- in the products. Since the solution is at pH=6 which is slightly acidic, we know that there are more products in the solution because H3O+ is o...

Deepika Reddy 1A

Buffer solutions can only be made with a weak acid and its conjugate base or a weak base and its conjugate acid. This is because a strong acid or strong base completely dissociate in a solution so that at the end, none of the substance is present in the solution at the end of the reaction. For weak ...

Deepika Reddy 1A

An irreversible reaction is one where the pressure remains constant. The second law of thermodynamics states that the entropy of the surroundings always increases. This would apply to irreversible reactions. However, entropy remains constant with reversible reactions because only infinitesimally sma...

Deepika Reddy 1A

Oxidizing agents are substances that cause other substances to become oxidized which causes themselves to be reduced. For reducing agents, they themselves are oxidized and they cause other substances to be reduced. The main thing to remember is that these names are indicating what these substances a...

Deepika Reddy 1A

Free energy is the energy that is available to do work.

Deepika Reddy 1A

G knot indicates that the substances in the equation are all in their standard or most pure states. You will get different answers when solving for either G or G knot but they can be related using the equation mentioned before in another answer.

Deepika Reddy 1A

I agree. Open systems are able to exchange matter and energy with its surroundings. I think the important thing is looking at whether the pressure is constant or not or if the volume is constant or not in deciding what equations to use.

Deepika Reddy 1A

Specific heat is in terms of grams while molar heat is in terms of moles. Specific heat is the heat capacity divided by mass in grams while molar heat is heat capacity divided by the moles.

Deepika Reddy 1A

Enthalpy is a state function which means that only the initial and final enthalpy values matter. The pathway taken does not matter. Therefore, because we know the enthalpy for the reaction at 200 degrees C, we make the pathway in a way where the initial and final would still be the same but it will ...

Deepika Reddy 1A

If you increase the pressure of the reaction, the reaction will shift to the side with fewer moles of gas. If you decrease the pressure of the reaction, the reaction will shift to the side with the greater number of moles of gas. A change in pressure causes a shift in the reaction because it alters ...

Deepika Reddy 1A

I believe they explained this in the pizza rolls review session. They said that even if molecules are at 0 Kelvin, they still have positional entropy. In order to have no entropy, the molecule at 0 K has to be perfectly ordered.

Deepika Reddy 1A

I believe the shape affects how many different shapes or positions the atoms in the molecule can be in. Since entropy is associated with the number of states or positions the atoms in a molecule can take, the shape of the molecule is associated with entropy.

Deepika Reddy 1A

The volume is expanding in b but it is expanding in a vacuum. What this means is that the external pressure is zero, so there is no force that is opposing the expansion being doing by the system. Work is only done when there is an opposing force that needs to be pushed against. Since there is no opp...

Deepika Reddy 1A

I believe the standard reaction enthalpy should always be in kJ/mol. If it is just the enthalpy value, it is in kJ.

Deepika Reddy 1A

Equilibrium means that it is a dynamic equilibrium and a reaction is occurring in the forward and reverse directions. Therefore, if it is at equilibrium, it is reversible.

Deepika Reddy 1A

State functions are when you only care about the initial and final values but the path taken to get to these values is not important.

Deepika Reddy 1A

The system does not exchange matter with the surroundings if it is a closed system.

Deepika Reddy 1A

A phase change can be between solids and liquids or liquids and gases. It takes a certain amount of energy for the phase to change.

Deepika Reddy 1A

Enthalpy is the heat of the reaction. If it is negative, then the reaction is exothermic. If it is positive, then the reaction is endothermic.

Deepika Reddy 1A

If Q is smaller than K, then equilibrium will shift towards the right so that it makes more products and Q will equal K. If Q is larger than K, then the reaction will shift towards the reactants so that more reactants can be made in order to reach equilibrium.

Deepika Reddy 1A

It depends on what is changing in the reaction. If the number of moles are changing, the rxn will shift a certain way in order to get the system back to equilibrium. If the product is taken away, then equilibrium will shift towards the products and if product is added, equilibrium will shift towards...

Deepika Reddy 1A

In an exothermic reaction, the heat is on the products side of the reaction since the reaction is releasing heat. Therefore, when you increase the heat, the reactant side will be favored and the equilibrium will shift to the left.

Deepika Reddy 1A

You usually have to use the ICE table when you only have the initial concentrations or you need to calculate the equilibrium concentrations. If Ka or Kb are given with some concentrations, then you are usually using the ICE table and the Ka or Kb values to find any missing concentrations.

Deepika Reddy 1A

If the reaction has a positive enthalpy, then it is endothermic and is non -spontaneous as it requires heat in order to occur. If the reaction has a negative enthalpy, then it is exothermic and is spontaneous.

Deepika Reddy 1A

If a reaction loses heat so that the products have less heat than the reactants, then the enthalpy is negative. If a reaction gains heat in order to occur, then the enthalpy is positive.

Deepika Reddy 1A

You find the percent by putting the concentration of the conjugate acid or base over the initial concentration of the acid or base and then multiplying by 100 to get the percentage.

Deepika Reddy 1A

If K is less than 10^-3, that means that the reaction favors the reactants at equilibrium. This means that there are more reactants than products at equilibrium so barely any of the reactants turned into product as the reaction proceeded.

Deepika Reddy 1A

You do the concentration of the conjugate over the concentration of the acid or base and then multiply by 100%.

Deepika Reddy 1A

If the pressure is increased, then the reaction favors the side of the reaction that has fewer moles of gas. In class, he gave us C=n/V and said that the change in concentration caused by the change in volume is what affects the reaction.

Deepika Reddy 1A

The table is using K to represent Kp. For the reactions that the Kc and K values are the same, the moles of gas on both sides of the reaction is probably equal. This would mean that Kc=Kp, so therefore in the table, K is equal to Kc for those reactions.

Deepika Reddy 1A

They are the same rule. If you disregard the x because K is less than 10^-3, at the end you can also check if it corresponds to the 5% rule. If it does follow the 5% rule, this means that the substance barely dissociates so K is small so it was correct to disregard x.

Deepika Reddy 1A

Ka is the equilibrium constant for an acid reaction while Kb is the equilibrium constant for a base reaction. Ka is related to pKa because pKa= -log(Ka) while pKb is related to Kb because pKb =-log(Kb). The larger the value of Ka, the stronger the acid and the larger the value of Kb, the stronger th...

Deepika Reddy 1A

Le Chatelier's Principle is helpful because it shows us how a reaction gets back to equilibrium after it has been changed in some way that causes it to not be at equilibrium anymore. This is helpful because it allows us to predict whether the reaction will favor the products or the reactants in orde...

Deepika Reddy 1A

The K and Kc values are the same things. Therefore, there is no conversion you need to do between the two. I believe they will specify Kp if it is the one being used.

Deepika Reddy 1A

When you take away a product you are stressing the reaction and shifting it away from equilibrium. In order for it to return to equilibrium, the reaction needs to make enough product again for the reaction to return to the same equilibrium K value. Therefore, by taking away a product, the reaction n...

Deepika Reddy 1A

Le Chatelier's principle predicts how a change in the physical parameters and other factors in a system affects a reaction and makes it no longer at equilibrium. It predicts whether the reactants or products will be favored in order for the reaction to go back to equilibrium.

Deepika Reddy 1A

It has to do with the equation C=n/V. This equation shows that if the volume is changed then the concentrations also change. For example, when the volume is halved and the pressure is doubled, the concentration of the reactants and products changes. This causes the reaction to no longer be at equili...

Deepika Reddy 1A

The E on the AXE is just the lone pairs on the central atom.

Deepika Reddy 1A

When the complex ion is an anion, then you have to add -ate to the end of the transition metal name. Some of the metals have exceptions, and have ate added a different way which just has to be memorized.

Deepika Reddy 1A

I think you just have to memorize the diagonal trend in the periodic table. The metals and oxides formed by some of these elements are amphoteric.

Deepika Reddy 1A

Dr. Lavelle, I hated chemistry before your class but you made the topics fun to learn and easy to understand. There were so many resources if we needed help too, which is something a lot of other classes don't have. This was my first quarter at UCLA and I'm so glad I took this class. I'm so excited ...

Deepika Reddy 1A

Strong acids and strong bases are substances that completely dissociate in water. Their conjugates are unreactive and are unable to reform the acid or base.

Deepika Reddy 1A

The stronger the IMFs, the higher the boiling point. For example, it takes more energy to break dipole-dipole IMFs than to break London dispersion IMFs because dipole dipole forces are stronger. Therefore, by looking at the IMFs, we can predict which substances have a higher boiling point.

Deepika Reddy 1A

HClO2 is the stronger acid because it has more oxygens. The oxygens make the conjugate base, or anion, more stable. This is because of resonance, where the negative charge on the oxygen delocalizes over the entire molecule, which stabilizes it.

Deepika Reddy 1A

A strong base is a hydroxide or oxide of the Group 1 or Group 2 metals. It dissociates almost completely in water, producing a lot of hydroxide ions. It causes the pH to rise a lot. A weak base only partially dissociates and causes less of a change in the pH.

Deepika Reddy 1A

For hybridization, you look at the valence electrons of the carbon because those are the ones that take part in bonding. So, since the valence electrons in carbon are in the second energy level, the hybridized orbitals have the number two written in front of them.

Deepika Reddy 1A

I'm not completely sure if we have to know Arrhenius acids or bases, but Arrhenius acids are just substances that dissociate into protons in the water. Arrhenius bases are substances that dissociate into hydroxide ions in water.

Deepika Reddy 1A

Yes, I believe that the coordination number is the number of points at which a ligand is attached to a central atom.

Deepika Reddy 1A

Yes, I think they do. By counting then number of lone pairs and bonding regions, I believe it is possible to figure out the hybridization. For example, for seesaw I believe it would be dsp3.

Deepika Reddy 1A

I believe that you would have to know the solubility rules. If something is soluble, then it shows up as ions. If the solubility rules says that a molecule or compound is not soluble, then the molecule or compound is written together and not dissociated into ions.

Deepika Reddy 1A

A Lewis Acid is one that accept an electron pair while a Lewis base is one that can donate an electron pair. A Bronsted acid is one that donates protons while a Bronsted base is one that accepts protons. Finally, an Arrhenius acid is a substance that dissolves to increase the number of protons in wa...

Deepika Reddy 1A

Boiling point can be determined by looking at the strongest intermolecular force that a substance has. If it has a stronger intermolecular force, then it has a higher boiling point. If both substances have london dispersion forces as their strongest IMF, then look at the size of the molecules and th...

Deepika Reddy 1A

The higher the electronegativity, the closer the bond gets to being an ionic bond. Ionic bonds are stronger than covalent bonds. Therefore, this tells us that the higher the electronegativity is, the more the atoms are attracted to each other. The higher the electronegativity, the stronger and short...

Deepika Reddy 1A

If the dipole moments cancel out, then most of the time that means that there is symmetry. Dipole moments occur when atoms do not share their electrons equally, causing the electrons to be pulled one way. If dipole moments cancel out, then the molecule is nonpolar. If they do not, then the molecule ...

Deepika Reddy 1A

I believe that a majority of the time, only transition metals are able to form coordination compounds and are the central atoms of them. This is because they normally do not make bonds like the main group atoms do. Main group atoms will normally form covalent or ionic bonds, however it is sometimes ...

Deepika Reddy 1A

A strong acid and base reaction will have equilibrium lie far to the right because they both dissociate almost completely into products. This means that at the end of the reaction, there will be more products than reactants. A weak acid and base will have equilibrium lie far to the left and at the e...

Deepika Reddy 1A

Everything has dispersion forces. Nonpolar molecules can only have london dispersion intermolecular forces. Polar molecules also have dipole-dipole in addition to london dispersion forces. You can tell the type of intermolecular force based on the charges on the substance, either full charge, partia...

Deepika Reddy 1A

I believe that drawing a Lewis structure is the best way to determine the AXE formula and see the lone pairs.

Deepika Reddy 1A

It is because the lone pair has a lot of electron repulsion so it pushes the atoms around it away from it. This causes the atoms to get closer together as they are repelled by the electrons in the lone pair, causing the bond angles to get smaller.

Deepika Reddy 1A

I believe distort is referring to the electron cloud surrounding molecules.

Deepika Reddy 1A

I do it by looking at which atom is more electronegative. The arrow points at whichever atom is more electronegative because it pulls on the electrons more.

Deepika Reddy 1A

The lone pairs and bonded atoms are regions of electron density. These regions will cause repulsion with other regions, which affects the molecule geometries and bond angles, as these regions will want to be as far as possible from other regions in order to be the most stable.

Deepika Reddy 1A

All molecules have LDF. They are considered the weakest because they are temporary charges that occur due to a temporary unequal balance of electrons. Therefore, since they are temporary partial charges, they are the weakest.

Deepika Reddy 1A

Since AT is held by two hydrogen bonds, these bonds are broken more easily. GC is held by three hydrogen bonds, so it is harder to break the bond between them.

Deepika Reddy 1A

If something is highly polarizable, that means that its electrons are more easily distorted. Large anions are larger atoms because extra electrons are added to the atom causing electron-electron repulsion, causing the atom to be bigger. This causes the electrons to be farther away from the positivel...

Deepika Reddy 1A

The greater the difference in electronegativity is between the two atoms, usually greater than two, then it is an ionic bond. This is a step above a polar covalent bond, which has an electronegativity difference that is less than that of the atoms in an ionic bond.

Deepika Reddy 1A

I think the interaction potential energy is always negative because whenever atoms interact, they are doing so because they want to be more stable than they are when they are alone. Therefore, energy is always released and the potential energy is negative because when atoms form a bond, they are bec...

Deepika Reddy 1A

This is because when they use the + or - , you should use the range. You do this by multiplying the value by two so that you get the range and can substitute that into the equation.

Deepika Reddy 1A

This equation gives the energy of the level that the electrons are on. With it, you can calculate the energy of two different levels, and then do the final minus the initial to get the energy difference between the levels. This will give you the energy that the electron either absorbed to jump up or...

Deepika Reddy 1A

The octet rule is that an atom wants to have enough covalent bonds to have a full shell of eight electrons so it is stable and resembles the configuration of a noble gas.

Deepika Reddy 1A

Yes, to find the number of moles, you would divide the amount of atoms by Avogadro's constant.

Deepika Reddy 1A

This means that the electrons aren't concentrated around just on atom. Instead, they are delocalized and they go between the different atoms in the molecule, instead of being associated with just one atom in the molecule. This makes the resonance structure more stable.

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