CHEMISTRY COMMUNITY

Armen_Isayan_2L

Hello, for this question you would utilize the equation [A]t = -kt + [A]0, which you would then need to rearrange t, to determine the amount of time. The rearranged equation would be t = [A]0-[A]t / k, and all you would have to do is input the proper values to determine the number of seconds it woul...

Armen_Isayan_2L

Hello! In order to find the units of k, you must consider that each order of reaction contains the same units of k. This is because the unit utilized in the end must be M/s. For instance, in a zero-order reaction the ultimate unit would be M/s, and this is due to the fact that no other units are mul...

Armen_Isayan_2L

Hello! In order to perceive the rate determining step, it is actually the slowest step in a reaction mechanism. Considering that the slowest step in the mechanism is the overall rate, explains its limitation. Therefore the rate determining step is used to determine the rate law for the overall react...

Armen_Isayan_2L

Hello! In order to solve this problem, you must utilize the second-order half-life equation, t1/2 = 1/k[A]0, except you must rearrange this equation so that k is isolated, k = 1/t1/2[A]0. By utilizing this rearranged equation you will be able to solve for the rate constant. If you are still having t...

Armen_Isayan_2L

Hello! In order to find k, you can plug in any of the values from the experiments. For instance, in experiment 2, your equation would be as follows, 19.6 = k[32][175]^2. Ultimately, you would have to isolate k, and the result would be k = 0.00002.

Armen_Isayan_2L

Hello! For a zero-order reaction, the overall rate of the reaction is not dependent on the concentration of the reactants but rather it is dependent on k. However, depending on the set of conditions and type of reaction it varies.

Armen_Isayan_2L

Hello! The calculation of half-life is typically provided in seconds, however, for the final exam you should consider what unit is given by the rate constant. This is because the half-life requires the rate constant, if it is in seconds or hours, your half-life will be dependent on that.

Armen_Isayan_2L

Hello! The n value is perceived as the number of electrons that are transferred, in order to acquire the n value, you must look at the full balanced reaction and determine how many electrons have ultimately transferred between the reactants and products.

Armen_Isayan_2L

Hello! That is correct, as kreverse can be expressed as k', however, k' with the " ' " notation utilized could also be used as the pseudo-rate constant in a reaction. It is crucial that you are aware of all units before moving forward so that you do not mix them up.

Armen_Isayan_2L

Hello! In order to calculate the half-life of a first-order reaction the equation is: t½ = 0.693/k
To calculate the half-life of a second-order reaction the equation is: t½ = 1/k[Ao]
To calculate the half-life of a zero-order reaction the equation is: t½ = [Ao]/2k

Armen_Isayan_2L

Hello! Yes, the k value is a positive value since it is a proportionality constant. In the case that there is a negative sign in front of the value, it would imply that reactants are being consumed.

Armen_Isayan_2L

Hello! The sign of the cell potential connotes spontaneity. This is because when E is positive, the process is spontaneous. In the case when delta g is negative, it would imply that E is positive, hence the process is spontaneous.

Armen_Isayan_2L

Hello! The pH meter fulfills measuring the acidity and the ion concentration of H+ in a solution. The importance of this is that it is useful in redox reactions and especially finding the overall concentration of a reaction.

Armen_Isayan_2L

Hello! The cathode can be identified as the species on the right of the cell notation, whereas the anodes are drawn on the left of the cell notation. This is because the anodes which are losing electrons are gained by the cathode.

Armen_Isayan_2L

Hello! Cp is identified as the heat capacity of a substance at constant pressure. I believe that it is important for the final as you would utilize Cp to find q as pressure is constant.

Armen_Isayan_2L

Hello! A higher atomic means higher molar entropy due to the fact that the atom has gained more mass and radius. Therefore, this will create a greater possibility of disorder within the various positions.

Armen_Isayan_2L

Hello! In regards to lecture #17, the electromotive force is not always equal to the maximum potential difference. However, when the electromotive force is evidently equal to the maximum potential difference, no energy is passed through because the current flow is halted.

Armen_Isayan_2L

Hello! Yes, the oxidizing agent is the substance that has been reduced. The reducing agent then becomes the substance that will be oxidized.

Armen_Isayan_2L

Hello! In order to keep electrons flowing in a consistent direction, it is important that the anode is presented on the left and the cathods is present on the right. Therefore, yes, both anode and cathode have to be on a certain side in the cell diagram.

Armen_Isayan_2L

Hello! In order to calculate the number of moles in a cell given a reaction to plug into ΔG, it is important to consider n, which represents the number of moles of electrons. These moles of electrons are utilized in balancing the redox reaction which is plugged back into the equation.

Armen_Isayan_2L

Hello! Yes, we can assume that a cell and a battery could be utilized interchangeably in the course. Basically, they are the same thing, however, a cell is a single unit device whereas a battery consists of a group of cells.

Armen_Isayan_2L

Hello! In an adiabatic process, it is apparent that there is no heat flow between the system and its surroundings, hence it is certain that q=0. However, it is not certain that w=0, because work is not equal to 0 unless the change in internal energy is equal to 0.

Armen_Isayan_2L

Hello! An adiabatic system implies that the system does not allow for the transfer of heat, as the system does not transfer heat between its surroundings and back and forth.

Armen_Isayan_2L

Hello! Cell potential (E) is not a state function, but rather a path function because we must determine the path of the system as it is necessary. Hence we are unable to subtract the initial state from the final state for the ultimate value.

Armen_Isayan_2L

Hello! Trouton's rule states that the entropy of vaporization for many liquids is the same at 85 J mol. This does not apply to every liquid, but rather a significant portion of them.

Armen_Isayan_2L

Based on the calculated ΔSvap values, the way in which we would establish the order is based on the entropy values. The lower entropy values determine the higher valued liquid samples, whereas the higher entropy values determine the lower valued liquid samples.

Armen_Isayan_2L

Hello! The difference between an isothermal and an adiabatic process is that an isothermal process is identified by the fact that the temperature remains constant. On the other hand, an adiabatic process is identified by the fact that heat is not transferred nor is mass.

Armen_Isayan_2L

Hello! Yes, when we are adding equations the same rules that apply to delta H also applies to delta S. This is due to the fact that standard enthalpies and standard entropies are both state functions, hence the same rules apply.

Armen_Isayan_2L

The difference between qrev versus regular q is the qrev is significant in identifying the heat of the reversible reaction. On the other hand, q is representative of the overall heat in the reaction.

Armen_Isayan_2L

At lower atm, there is higher entropy because there is an increase in volume at lower pressures. In essence, at higher pressure there is a decrease in volume. As the volume increases at lower pressures, the particles are more reactive because of the space that particles are able to occupy.

Armen_Isayan_2L

Hello! Entropy it is the amount of disorder present in a system. Hence, when gas expands, the entropy increases because the gas molecules are more volatile and are constantly moving around.

Armen_Isayan_2L

Hello! In order to describe the concept of calorimeters, it is important to understand that a calorimeter is utilized in order to measure the transfer of energy through heat. In essence, the heat is either absorbed or released, and depending on that, it will determine if it is transferred between a ...

Armen_Isayan_2L

Hello! In order to determine which systems do on the surrounding, it is important to understand that if the work in question is negative, then the gas is gradually expanding and doing work on the surroundings. However, if the work is actually positive, the gas is not expanding, but rather compressin...

Armen_Isayan_2L

Hello! Heat capacity cannot be negative. This is primarily because heat capacity is emphasized by the amount of energy necessary in order to raise a particular substance's temperature. Ultimately, it is a positive process.

Armen_Isayan_2L

Hello! There is not a direct relationship between the strength of the bonds in a reaction and whether or not that reaction is endothermic or exothermic. Rather it is crucial to understand that the side of the equation which contains a larger sum of bond enthalpies, determines if it is exothermic or ...

Armen_Isayan_2L

Hello! A method of identifying neutralization is the formation of the products, water, and salt. This occurs through a neutralization reaction, which is the combination of a strong acid and a strong base. This combination results in the production of water and salt, hence identifying the neutralizat...

Armen_Isayan_2L

Hello! When you increase temperature, the K value increases for an endothermic reaction because heat is a reactant. In essence, heat is crucial in an endothermic reaction so that it occurs in the forward direction. As the temperature rises, the reaction will shift right, which will ultimately produc...

Armen_Isayan_2L

Hello! Both K and Kc are relatively the same thing, they are both equilibrium constants. In essence, Kc is in reference to being associated with molar concentrations, whereas K is associated with partial pressures.

Armen_Isayan_2L

Hello! The sole factor which affects the equilibrium constant K is temperature. Also, depending on the type of reaction which is associated with the direction of change in K, whether endothermic or exothermic will explain if K increases or decreases. In an endothermic reaction, K will increase and i...

Armen_Isayan_2L

Hello! It is evident that pressure does not tka significant effect upon liquids or solids. This is mainly because of the fact that pressure tends to effect only gases, and not liquids and solids, hence a change in pressure will to affect a reaction, in the case that a reaction contains the exact sim...

Armen_Isayan_2L

Hello! When creating an ICE box, you usually use -x when the concentration is presented as the initial, because that particular molecule will likely decrease, hence that side of the reaction would be represented by -x. On the other hand, the other side of the reaction would be presented by +x.

Armen_Isayan_2L

Hello! In order to know when to use the ideal gas law it is important to consider which units and variables have been provided in the question. For instance, if the units such as, temperature, volume or mole have been utilized then the ideal gas law is the best solution to find the missing variable

Armen_Isayan_2L

Hello! A phase change is in regards to a substance changing from one state of matter to another, in essence from one phase to another phase as well. It is important to note that when a substance undergoes a phase change, it will take place under different temperate conditions, such as melting and bo...

Armen_Isayan_2L

Hello! It is crucial to remember that when you are completing your ICE box that you include only aqueous solutions and ages. Hence, if H2O is expressed to be. a gas, then you should include it in the ICE box, however, if it was not, you would not include it.

Armen_Isayan_2L

Hello! Hess's Law states that the change in enthalpy is actually a fixed quantity given particular conditions and it is entirely independent of reactions and its number of steps to obtain it, it is also a state function.

Armen_Isayan_2L

Hello! We use the ICE box when we are solving for the equilibrium concentration of both products and reactants and attempting to track the change that took place from the initial concentration. Most of the time the initial concentration is provided in the question and that is when we'd have to use t...

Armen_Isayan_2L

The temperature can change mid-equation, this is because K is heavily dependent on temperature. Hence, if the temperature changes, the next step would be to find the two separate values of Q for each temperature. In this case, you would indicate the two separate values of Q, as it may appear on an e...

Armen_Isayan_2L

Hello! It is likely that the question will indicate the value of delta H which you will be able to use to determine whether or not the reaction itself is endothermic or exothermic. In essence, finding out whether it is an endothermic or exothermic reaction, should display how the reaction will respo...

Armen_Isayan_2L

Hello! Yes, the left side is always reactants and the right is the product based on equilibrium. In essence, the two reactions, the forward and reverse reaction, the forward reaction is a reactant to the product. However, in the case that the equation is reversed, the yield would be that of the forw...

Armen_Isayan_2L

Hello! Typically, we only use the ICE box method for weak acids and bases because of the nature of the solutions and the amount that will dissociate is difficult to determine. However, we can still use the ICE box method for strong acids and bases, but it is not necessary. Instead, we could use form...

Armen_Isayan_2L

Hello! Total pressure is identified as the combined pressures of gases that are given within the reaction. Once you create an ICE table you can add all the equilibrium pressures together to determine the total pressure.

Armen_Isayan_2L

It is evident that concentrations cannot be deemed negative since it is defined by moles, you cannot have a negative mole per litre. Hence, concentrations are positive.

Armen_Isayan_2L

The main occurrence which takes place to cause a change in K is a change in temperature, however, factors such as a change in temperature causes a shift in the equilibrium. The factors which also take place to cause a shift in the equilibrium are offset to shift back to equilibrium. This ensures tha...

Armen_Isayan_2L

According to Le Chatelier's Principle the dynamic equilibrium could also be disturbed by conditions such as change in pressure or concentration of products or reactants. However, the equilibrium will automatically shift oppositely to the change that took place, to eliminate the change and initiate d...

Armen_Isayan_2L

When you are prompted an ideal gas law, you would expres the temperature in Kelvin. If you are prompted the temperature in units of Celsius you would just convert to Kelvin.

Armen_Isayan_2L

The difference between a real and ideal gas, is that an ideal gas has no definite volume while a real gas has an established and definite volume. Also while analyzing the collisions which take place between the particles in both real and ideal gases, the real gases have non-elastic collisions and id...

Armen_Isayan_2L

Hello, in order to be certain if something is acidic or basic we know that anything below a pH of 7 is acidic, a pH of 7 is neutral, and anything below a pH of 7 is acidic. To be even more certain, you could determine the value of the pKa to find the strength of an acid, and in turn determine the pH.

Armen_Isayan_2L

Hello! A polyprotic acid are acids that lose various protons per each molecule during reaction that involve both acids and bases. On the other hand a polyprotic base accepts at least one hydrogen proton per acid-base reaction.

Armen_Isayan_2L

Hello, the main difference between the Bronsted and Lewis acids and bases is that Bronsted acids donate protons and the Bronsted bases accept protons. On the other hand Lewis acids are electron pair acceptors and the Lewis base donates electrons.

Armen_Isayan_2L

Hello, you would need 50% of all the points contributed to your grade to earn a C- in the class, which is a passing grade.

Armen_Isayan_2L

Hello! In order to detemrine the bond length we would have to consider the atomic radius. Utilizing the atomic radius, we would total the radius of the atoms up. If the bond in question is a covalent bond we would both the radius of the covalent bond and we would do the same for an ionic bond.

Armen_Isayan_2L

Hello, all organic acids contain a carbon atom, because it is crucial to its structure, therefore carbon must exist in the structure of a organic acid for it to be considered one. On the other hand, inorganic acids do not contain carbon, however there do exist some inorganic acids that do contain ca...

Armen_Isayan_2L

Hello! In order to determine the number that goes after the metal of a compound, you must determine the charge and write it in roman numerals after the metal.

Armen_Isayan_2L

Hello! A coordination number is described by the number of atoms or ions that the central atom is bonded to. It is important to figure out because it allows to determine the name of the coordination complex.

Armen_Isayan_2L

Hello! Lone pairs of electorns on molecules occupy more space than bonded electrons since they have significant repulsion strength they are attracted by the single nucleus, hence illustrating that through a short distance they are spread out from the nuclues which they are attracted to.

Armen_Isayan_2L

Hello! When dipole moments cancel eachother out, the molecule is considered nonpolar, however, the molecule must be completely symmetric so that the dipole moments would be able to cancel each other out. The shape of the molecule plays a significant role on its polarity, for instance, if the molecul...

Armen_Isayan_2L

Hello! To find a conjugate acid, a hydrogen atom is added, and to find a conjugate base the hydrogen atom would be removed.

Armen_Isayan_2L

Hello! The best manner to describe a acid-base pair is to highlight the presence of the hydrogen atom and the existing charge. For instance, a conugate acid contains an extra hydrogen atom and a proton is added to the base. On the other hand, a conjugate base is lacking of the extra hydrogen atom an...

Armen_Isayan_2L

A molecule that has a lone pair is not necessarily always polar, most of the time it is, however, the arrangement of the molecule, if it is symmetrical, plays a significant role in determining its polarity.

Armen_Isayan_2L

Hello, Pi bonds are solely applicable to covalent bonds! In essence, they are covalent bonds thare able to form into double or triple bonds, but do not form into single bonds.

Armen_Isayan_2L

Hello! the difference between a localized and delocalized bond is that the electrons remain close to the atom, and it travels between the two atoms. On the other hand, a delocaized bond is indicative of electrons that do not remain close to one atom, but instead are close to two atoms, visiting both.

Armen_Isayan_2L

Hello! The distinction between a Pi bond and a Pi molecular bond is that a Pi bond is the result of an overlapping of orbitals that come into contact with each other through the area that is overlapping. However, a Pi molecular bond is identified as the nodal plane which is existing between two atom...

Armen_Isayan_2L

Hello! The method which I typically utilize to determine if the bonds distanced between the atoms in the molecule or covalent or ionic, is by determining the space found between the atoms on the actual periodic table. For instance, for the atoms which are close, they are usually ioninc bonds, howeve...

Armen_Isayan_2L

Hello! Degenrate orbital are known as electron orbital which express the same energy levels, however, according to Hund's rule the orbital must be filled evenly before the elctrons are transferred to higher energy levels.

Armen_Isayan_2L

Hello! The trend for effective nuclear charge on a periodic table is that it increases from left to right of the table, however, it decreases down a group.

Armen_Isayan_2L

Hello! In order to determine ionic and covalent character you must assess the difference between electronegativity, this is because if there is a large difference in electronegativity, it is likely the bon will be ionic. However, the less difference there is in electronegativity the more likely it w...

Armen_Isayan_2L

Hello! If it is in the same row and right next to each other, the atom on the right would have the higher electron affinity, this is because electron affinity gradually increase as you move from the left to the right of the periodic table.

Armen_Isayan_2L

Hello! This is because those elements which share similar chemical properties are naturally grouped together, it makes it easier to find and analyze these elements.

Armen_Isayan_2L

This is because the metallic character is greatest in the lowest left corner of the periodic table because it is easier for the elements in the lowest left corner of the periodic table to lose atoms.

Armen_Isayan_2L

Hello! Atoms are more electronegative going from the left to the right of the periodic table because the number of charges within the nucleus increase, hence increasing the electronegativity. In essence, as the electronegativity increases, the atoms are able to bond with electrons more easily. Also,...

Armen_Isayan_2L

Hello! A Lewis acid is the substance which accepts electrons, an electron-pair acceptor. Whereas the Lewis base donates electrons, an electron-pair donor.

Armen_Isayan_2L

Hello! In order to determine the most stable structure among various resonance structures, it is crucial to find the resonance structure with the least amount of charges. This will indicate how stable it is in reality. Also within the structure, the most electronegative atoms will have negative char...

Armen_Isayan_2L

Hello, in order to calculate the electronegativity of an atom, we take the two elements from the chemical formula, and we subtract the smaller electronegativity from the larger electronegativity to determine the type of bond. It is important to remember that as you move up and to the right of the pe...

Armen_Isayan_2L

To further understand the trends within the periodic table I would recommend writing down the trends you have a difficulty familiarizing yourself with on a flashcard and you can test yourself. Later you could apply the concepts you tested yourself on to the actual periodic table to see if the flashc...

Armen_Isayan_2L

Hello! Electrostatic potential energy is essentially the potential energy of a proton in regards to its positioning near a molecule. The more negative the electrostatic potential energy becomes, an attraction is formulated between the proton and molecules.

Armen_Isayan_2L

Hello! An effective nuclear charge is the net change, which is usually positive, that the outermost electron shell experiences. The effective nuclear charge tends to be a lower value than the actual nuclear charge.

Armen_Isayan_2L

Hello! isoelectronic atoms are described as two atoms, ions, or molecules that contain the same electron configuration. They do indeed have the same number of electrons, but their properties are different, hence they will not have the same charge. Also the electronegativity is dependent upon how man...

Armen_Isayan_2L

According to Hund, electrons in the ground state, which is the lowest energy electron configuration, would finally have electrons become parallel. Hence, each orbital of the sub shell is occupied with electrons of parallel spin.

Armen_Isayan_2L

Hello! This is best understood through understanding the trend of electronegativity, which is an atoms likelihood to attract a shared pair of electrons. As you move from the left to the right end of the periodic table the, more electronegative the atoms are. In essence, cations are described as posi...

Armen_Isayan_2L

Hi, this is best explained by the orbitals distance from the nucleus. For instance, as the s orbital is closer to the nucleus than the p orbital is, the p orbital has electrons that are farther out from the nucleus which demonstrates that it is at a higher energy level. Hence, the shielding of the p...

Armen_Isayan_2L

Hello! The 'spin' is best described as a property of electrons and this term is utilized because electrons seem to contain an angular momentum that rotates the electron. It just seems that they are spinning, however, in reality the subatomic particles are just spinning in a very rapid motion.

Armen_Isayan_2L

Hello! Elements with the same number of electrons contain the same properties as the number of electrons dictates the chemical behavior of the electrons.

Armen_Isayan_2L

To find the maximum number of electrons that can be ejected from metal when given a total energy you would have to first find the energy per photon, and then divide that by the total energy.

Armen_Isayan_2L

The rounding range is usually contingent on how many sig figs you should be using to answer the problem.

Armen_Isayan_2L

I believe this is due to the fact that Oxygen has lower ionisation energy than nitrogen as a result of an electron being added to a half full orbital in the Oxygen. This makes Oxygen one of the few outliers that don't follow the ionization energy trend in the periodic table.

Armen_Isayan_2L

Use a regular v for velocity. As for the frequency v, I just add a small tail in the beginning and that should help you differentiate between your frequency and velocity v's.

Armen_Isayan_2L

Although electron affinity and electronegativity share some similar aspects, they are not the same. Electron affinity is a measure of the change in energy when a neutral atom attracts an electron to become a negative ion, while Electronegativity refers to the ability an atom has to attract electrons...

Armen_Isayan_2L

Hi, it is important to understand what the questions is asking to fully solve the problem. In this instance, since the question mentioned using the De Broglie equation to solve the problem, 2.5 micrometers is indeed supposed to be the wavelength.

Armen_Isayan_2L

In order to convert from meters to nanometers you would have to multiply the figure that has been presented by 1,000,000,000 (10^9).

Armen_Isayan_2L

Hello Katie, the mass of the atoms should be presented in kilograms because it is the SI unit for mass. Unless, an actual unit is specified it is best to utilize kilograms as the unit for the mass.

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