CHEMISTRY COMMUNITY

Jonathan Gong 2H

My reasoning would be that it is the interactions between the reactant species that drive the reaction to produce products. Thus, it would be the concentrations of the reactants that would influence/determine the rate of a reaction.

Jonathan Gong 2H

To solve 6.45, you have to look at each species' standard reduction potentials and compare them.

Jonathan Gong 2H

Temperature does affect the rate of reaction. But, I think that it really only factors in when you are trying to compare rates of reaction/rate constants at 2 different temperatures.

Jonathan Gong 2H

A catalyst lowers the activation energy of a reaction but is not consumed. If you look at the elementary steps of a reaction, you will see that a catalyst is present as a reactant at the very beginning of a reaction, but is also produced as a product at the end. This means that is was not "cons...

Jonathan Gong 2H

They are the exact same equation, just written in different forms.

Jonathan Gong 2H

Maybe. The format of the final was never specified by know that it will be straightforward and open book.

Jonathan Gong 2H

The rate limiting step or the rate determining step is the slowest step of the reaction (of the elementary steps) that determines the rate at which the overall reaction proceeds. Usually the questions will give us which step is slow/fast. If we are given the rate law of the reaction, the slow step o...

Jonathan Gong 2H

For part b, use the equation for the first order integrated rate law... ln[A] = -kt + ln[A]initial. Then, plug in the given values, making sure that the units match up between time and rate constant, and then solve for [A].

Jonathan Gong 2H

The net rate of formation for a reaction is equal to the rate of formation in the forward direction plus the rate of formation in the reverse direction. At equilibrium, it should be equal to 0.

Jonathan Gong 2H

You can tell that OH- is a catalyst in this reaction because it is consumed in step 1 as a reactant but formed again as a product in step 2, thus making it present throughout the reaction. The difference between a catalyst and an intermediate is that an intermediate is usually created by a step but ...

Jonathan Gong 2H

I think questions usually give us which step is the slow step and which step(s) are the fast step(s). And, since the slow step is the rate-determining step, you can use the experimental rate law.

Jonathan Gong 2H

The part of this I'm getting stuck on is the oxidation half-reaction. Could someone explain how they got the oxidation half-reaction step by step of Cl2 + S2O3 ^2- --> Cl^- + SO4 1) S2O3^2- --> SO4^2- Balance S 2) S2O3^2- --> 2SO4^2- Balance O, Acidic Solution 3) S2O3^2- + 5H2O --> 2SO4^2- Balance H...

Jonathan Gong 2H

A 1st order graph is given as ln[A] = -kt + ln[A]o. So yes, -k is the slope/it is m in the equation y = mx+b.

Jonathan Gong 2H

If Gibbs free energy is negative/lower, the reaction will be spontaneous, which means that it will proceed in the forward direction towards the products. This means that the products of that reaction are more stable than the given reactants.

Jonathan Gong 2H

Rate constants, k, should be positive since they relate given concentrations with the rate of a reaction, which will always be positive. But, if you are considering graphs, a plot of a 1st or 0 order reaction will have a slope of -k, while a plot of a 2nd order reaction will have a slope of +k.

Jonathan Gong 2H

A first order reaction is a reaction that depends linearly on reactant concentration. This means that if the concentration of one reactant were to double, then the initial rate of reaction would also double.

Jonathan Gong 2H

Yes, deltaS system and deltaS surroundings will be equal but opposite signs in this question.

Jonathan Gong 2H

You change the sign of the reduction potential of the anode/cathode half-reactions based off of the direction of the half-reaction. For example, for Cu2+ + 2e- -> Cu, the standard reduction potential is 0.34 V. But, if this reaction occurs at the anode, then the half-reaction will actually be CU -> ...

Jonathan Gong 2H

A salt bridge in a galvanic cell maintains charge neutrality between the two half cells so that the cell can continue to function. It does this by containing inert ions that can flow to each of the half cells to balance out the built up charge caused by the transfer of electrons.

Jonathan Gong 2H

Standard reduction potentials of half-reactions will be given to us. We will have to solve for E cell given these values.

Jonathan Gong 2H

Since electrons flow from the anode to the cathode, there will be a charge imbalance. So, to maintain neutrality and keep the galvanic cell functioning, a salt bridge, with inert ions inside of it, balances the charge in both half cells.

Jonathan Gong 2H

To think about an isothermal reaction/process, you can refer to the equation PV = nRT. In an isothermal reaction, the values represented by P and V, respectively, will either increase or decrease so as to maintain constant temperature. So, if pressure decreases, volume increases, which allows temper...

Jonathan Gong 2H

The difference of between the delta G equations pertains to the values that are given in the question. If given the equilibrium constant of a reaction, delta G can be calculated using -RTlnK. If given the enthalpy, entropy, and temperature, you can use delta H - T*delta S. If given initial concentra...

Jonathan Gong 2H

delta S naught is the entropy of the reaction at standard conditions. Since standard conditions are defined, delta S naught will be a constant/always have the same value.

Jonathan Gong 2H

delta G is just the overall Gibbs free energy. delta G naught is the Gibbs free energy of the reaction at standard conditions.

Jonathan Gong 2H

delta G is positive when K is less than 1 because the equation is dG = -RTlnK. When K is less than one, lnK is negative, which cancels out the negative sign and makes delta G positive. Vice versa, when K is greater than 1, lnK is positive, which makes delta G negative.

Jonathan Gong 2H

I think that the enthalpy given in the problem is enthalpy of combustion. Meaning that the enthalpy of formation of each respective molecule would be -enthalpy of combustion. Thus, when you do your calculations, it would be dHrxn = 1560 kJ/mol - 1300 kJ/mol - 2(286 kJ/mol). Which equals -312 kJ/mol.

Jonathan Gong 2H

Since both parts have to do with phase change, you can use dS = q/T = dH/T. Thus, the calculation is 1.00 mol(-6.01 kJ/mol)/273.15 K. And, the answer is -0.0220 kJ/K. For part b, you can use the same equation. First, calculate the moles of ethanol and multiply it by the molar enthalpy of vaporizatio...

Jonathan Gong 2H

In this case, delta U does = w. So the solution is delta U = 28 J.

Jonathan Gong 2H

4D.15 is solved using Hess's law which essentially states that the reaction enthalpy is equal to the sum of the products' reaction enthalpy minus the reactants' reaction enthalpy. In this problem, dH = 1560 kJ/mol - 1300 kJ/mol - 2(286 kJ/mol). Which is equal to -312 kJ.

Jonathan Gong 2H

I'm not sure exactly what you are asking for; however, kJ/mol is a perfectly valid unit.

Jonathan Gong 2H

They are the same thing.

Jonathan Gong 2H

NO2 has the higher molar heat capacity because there are more atoms and bonds to absorb the energy from temperature change.

Jonathan Gong 2H

Jonathan Gong 2H

Constant pressure can be assumed if a pressure is given and nothing in the problem says that it changes. It can also be assumed if the problem says that the reaction or system takes place at standard conditions, which would mean that they take place at 1 atm.

Jonathan Gong 2H

q is negative because it is not the combustion chamber that absorbs the heat, it is the cooling system that surrounds it. Thus, the combustion chamber is losing heat, which means that q should be -947 kJ when its internal energy or work is being calculated.

Jonathan Gong 2H

Work is negative because the volume has increased at constant pressure... which means that the system is performing work on its surroundings and has lost energy as a result.

Jonathan Gong 2H

Bonds are formed to increase stability. Thus, when they are formed, the system loses energy in order for stability to increase. This energy lost exothermically is usually heat.

Jonathan Gong 2H

If a piston is pushing on the system/compressing it, then work will be positive because deltaV is negative. This means that work is being done on the system. Generally, I like to determine what is influencing the other, so if the system is doing something or exerting some force on the surroundings o...

Jonathan Gong 2H

Yes, w = -P*deltaV. If deltaV is negative then work will be positive. But, it is also important to consider what the question asks and what entity the work is being done on for the sign of work.

Jonathan Gong 2H

In lecture, the two given reactions were as follows. (1) N2(g) + O2(g) --> 2NO(g). (2) 2NO(g) + O2(g) --> 2NO2(g). Since the product of the first reaction becomes a reactant in the second reaction, it can be canceled out on both sides of the reaction. Then, you would simply combine/add reactants wit...

Jonathan Gong 2H

DeltaHfus is the enthalpy change when a substance changes phase from solid to liquid (melts). DeltaHvap is the enthalpy change when a substance changes phase from liquid to vapor (vaporizes). And, deltaHsub is the enthalpy change when a substance changes phase from solid to vapor (sublimates). Delta...

Jonathan Gong 2H

A state property is a quantity whose value is independent of the path taken to reach a specific value. In this class, pressure, temperature, volume, enthalpy, density, and heat capacity are considered state properties. Work and heat are not because they depend on the path taken. For enthalpy, it mea...

Jonathan Gong 2H

If temperature is increased during an exothermic reaction, the formation of reactants is favored and the equilibrium constant will decrease.

Jonathan Gong 2H

If the reaction is endothermic and temperature is increased, the formation of products will be favored and the equilibrium constant will increase.

Jonathan Gong 2H

NO2- is the conjugate base of nitrous acid, so I think yeah, it would pick up a proton and make the solution basic. A buffer is a solution that can resist pH change upon the addition of an acidic or basic component. It can neutralize those additions and maintain the pH of the solution. As for neutra...

Jonathan Gong 2H

The forward reaction is exothermic, so it releases energy. The reverse reaction is endothermic, requiring energy. If temperature is increased, we are inputting heat into the reaction, which will shift towards the left/reactants.

Jonathan Gong 2H

A change in temperature does affect K because reactions are always are endothermic or exothermic. For example, if a reaction requires heat (endothermic) while forming product, then heating or increasing the temperature will favor product formation because there is more heat input into the system. On...

Jonathan Gong 2H

After searching this up, the rule it exists because values of Ka and Kb are typically known only to an accuracy of +- 5%. Thus, if the approximation is within 5%, we can consider it valid.

Jonathan Gong 2H

The solubility product constant is represented by Ksp, which is used for a solid dissolving in an aqueous solution. For example, for the reaction aA(s) --> bB(aq) + cC(aq), Ksp = [B]^b * [C]^c, solids are not included because their concentrations do not change. The greater the Ksp, the more soluble ...

Jonathan Gong 2H

The equilibrium constant for predicting solubility would be Ksp and can only be applied for solids dissolving in an aqueous solution. For a reaction such as aA(s) --> bB(aq) + cC(aq), Ksp can be determined by the equation Ksp = [B]^b * [C]^c. The higher the Ksp, the more soluble it is.

Jonathan Gong 2H

Hopefully I'm answering this question as you intended. Any change in volume will affect pressure. If volume increases, pressure decreases. Conversely, if volume decreases, pressure will increase.

Jonathan Gong 2H

In the C row goes the change in concentration or pressure. In this row, the change is represented by the variable x. E.g. [Cl] (numerical value) - x. Hope this helps.

Jonathan Gong 2H

Solids and liquids are excluded from the equilibrium expression because their concentrations stay constant throughout the reaction. In other words, they have no impact on reactant concentrations at equilibrium. Hope this helps.

Jonathan Gong 2H

Pa is a pascal, an SI unit of pressure. 1 pascal is equal to 10^-5 bar. I don't think we always have to do work in bar, just in the unit of pressure that is given in the question. I could be wrong though.

Jonathan Gong 2H

In a mixture of gases, each gas has a partial pressure which represents the pressure of that gas if it occupied the entire volume of the mixture, at the same temperature, by itself. Thus, the total pressure of the gas mixture is the sum of the partial pressures of each individual gas.

Jonathan Gong 2H

In total, there are 10 valence e-. Because both carbon and oxygen need to have an octet, there needs to be a triple bond.

Jonathan Gong 2H

Ag+ is a Lewis acid because it is an electron pair acceptor. This is because it has a positive charge and electrons will be electrostatically attracted to it. BF3 is a Lewis acid because if you draw its Lewis structure, it has three fluorines bonded about it but no lone pair. Since B only has 6 elec...

Jonathan Gong 2H

Jonathan Gong 2H

We should know all of the common acids/bases. Otherwise, you can see if a molecule fulfills the Bronsted-Lowry or Lewis requirements. A Bronsted acid is a proton (H+) donor and a Bronsted base is a proton acceptor. A Lewis acid is an electron pair acceptor and a Lewis base is an electron pair donor.

Jonathan Gong 2H

I think that dipoles only cancel for tetrahedral molecules when all four atoms attached to the center atom are the same.

Jonathan Gong 2H

An acid is stronger if it can lose hydrogen to a base more easily/if it dissociates in solution more basically. Formic acid is stronger because the CH3 in acetic acid is donating electrons. This adds electron density to the O-H bond (making the bond less likely to break), making it harder to remove ...

Jonathan Gong 2H

Amphoteric and amphiprotic are basically the same thing. However, amphoteric is more widely used because it does not require a substance to accept and donate protons. An amphiprotic substance specifically requires that an amphoteric substance transfer H+ ions. Hope this makes sense. Essentially, all...

Jonathan Gong 2H

I believe so.

Jonathan Gong 2H

Yes, you would write the chemical symbols of ligands in alphabetical order. But, when different ligands contain the same element, those denoted by a single letter (e.g. O) take precedence over symbols represented by two or more letters (e.g. OH).

Jonathan Gong 2H

When you draw the Lewis structure of CO3^2-, one resonance has C=O double bond and 2 C-O^1- single bonds, these two O^1- are capable of binding to a metal center at 2 places, therefore making it a bidentate ligand. A different resonance of CO3^2- has the double bond between the two C-O bonds, leavin...

Jonathan Gong 2H

The number of points at which ligands are attached to the central metal atom is called the coordination number of the complex. For example, the coordination number is 4 in Ni(CO)4 and 6 in [Fe(CN)6]4-.

Jonathan Gong 2H

Yes, a radical counts as a region of electron density just as a lone pair does. Although, the repulsions created by the unpaired electron will be weaker than that of a lone pair.

Jonathan Gong 2H

Chelating ligands are ligands which are able to form two or more coordinate covalent bonds with a metal ion. Chelates are complexes containing a ligand that forms a ring of atoms that includes the central metal atom. They are significant because they are another type of, albeit much larger and more ...

Jonathan Gong 2H

I'm pretty sure that sp2 is more stable than sp3 due to it having more s-orbital character. Since higher bond strength equates to higher stability, sp2 is more stable than sp3.

Jonathan Gong 2H

You don’t need to write E0, you can just not write it.

Jonathan Gong 2H

A radical still counts as 1 region of electron density, so in that sense, it's the same as a lone pair. However, it's not as strong as a lone pair.

Jonathan Gong 2H

Both are accurate and compatible with the molecular formula. It will most likely be specified whether the structure corresponding with the molecular formula is cis- or trans-. But, this is organic chemistry so I'm not sure if we really need to know this.

Jonathan Gong 2H

The central I atom has a trigonal bipyramidal shape, meaning there are 5 regions of electron density about it. The three lone pairs repel each other, meaning that they want to maximize their distance away from each other, thus, they take up equatorial positions with a 120 degree angle separating one...

Jonathan Gong 2H

An ion-dipole force is an attractive force that results from electrostatic attraction between an ion and a neutral molecule with a dipole. It will commonly be in solution. For example, Cl- and H2O.

Jonathan Gong 2H

The best resonance structure has a formal charge closest to 0 because it means that the atom has the best balance of bonds to lone pairs according to its valence, meaning that it is stable.

Jonathan Gong 2H

Bond lengths differ from single bonds and other bonds because it depends on the strength of the bond. As you know, a double bond is stronger than a single bond and a triple bond is stronger than a double bond. This means that the attractive forces between a two double bonded elements will be stronge...

Jonathan Gong 2H

Elements in the 3p or higher orbital are exceptions to the octet rule. This is because they have an empty d-orbital that allows them to hold more than 8 valence e-, e.g. for P, it is located in the 3p orbital, but has an empty 3d orbital that allows it to hold more than 8 e- and be an exception.

Jonathan Gong 2H

The stronger the intermolecular forces the higher the boiling point/melting point will be. Generally, polar molecules have dipole-dipole forces, making them have stronger intermolecular forces than nonpolar molecules, thus, they will boil/melt at a higher temperature.

Jonathan Gong 2H

Each resonance structure actually does matter because they all contribute to form what is called a resonance hybrid. The most stable resonance structure, the one with the formal charge closest to 0, contributes to the resonance hybrid more than the other, less stable structures. Hope this helps!

Jonathan Gong 2H

It is possible to have a temporary dipole moment. A molecule with a permanent dipole moment would be a polar molecule. Hope this helps!

Jonathan Gong 2H

Electronegativity is the tendency of an atom to attract electrons to itself. On the other hand, electron affinity is the measurement of the energy required when an electron is added to a neutral atom or molecule in the gaseous state to make it a negative ion. Hope this helps.

Jonathan Gong 2H

Different bonds (single, double, triple) have different bond lengths. So I guess that you could say that depending on the bond length, you can tell what the bond type is. Shorter bonds are also stronger and require more energy to break. Hope this helps.

Jonathan Gong 2H

Electronegativity is the tendency of an atom to attract electrons to itself. Electron affinity is the amount of energy required when an electron is added to an atom or molecule in its gaseous state to form a negative ion. Hope this helps.

Jonathan Gong 2H

Atoms in period 3 or higher have a d-orbital in their valence shell which allows them to accommodate more valence e-. In terms of drawing a Lewis Structure, the extra 2 e- would be drawn as lone pairs. Hope this helps.

Jonathan Gong 2H

To make sure that you draw the most efficient Lewis Structure you could always draw all resonance structures first. After, you can calculate the formal charge for atoms of each structure and determine which one is most efficient.

Jonathan Gong 2H

Fluorine is the most electronegative element because it has 5 electrons in its 2p shell. Since fluorine is close to the ideal electron configuration of 6 electrons in its p shell and given that it has a relatively small atomic radius paired with its nuclear charge, fluorine is the most electronegati...

Jonathan Gong 2H

This is because bromine can accommodate more than 8 valence e- in what is known as an expanded valence shell. Generally, atoms in period 3 or higher have a d-orbital in their valence shells, allowing them to have more than 8 valence e- in a bond/Lewis structure. Hope this helps.

Jonathan Gong 2H

When an atom is ionized, electrons are alway removed from the outermost shell. In this example, Ru3+, the outermost shell is 5s. Thus, 2 electrons are removed from that s orbital while 1 electron is removed from the d orbital. This leads to the electron configuration [Ar] 4d^5. Hope this helps.

Jonathan Gong 2H

Elements/atoms in period 3 or higher have a d-orbital in their valence shell, allowing them to accommodate more than 8e-. For example, P, S, and Cl. Hope this helps.

Jonathan Gong 2H

396 x 10^1 m/s is exactly the same as 3.96 x ^ 3 m/s. Therefore, both answers are correct. However, conventional scientific notation will be 3.96 x 10^3 m/s, so it would probably be better if the answer you wrote down was the latter.

Jonathan Gong 2H

For this question, you are going to be using the De Broglie wavelength equation which is wavelength = h/momentum, which can be derived to be wavelength = h/mass*velocity. In this question, velocity is the same, however, the mass of the proton and neutron is slightly different. Ultimately though, aft...

Jonathan Gong 2H

For minimum uncertainty, you would use 5.00 m/s as the velocity of the bowling ball.

Jonathan Gong 2H

How do you find the values of ml, and what do those values specifically signify? Given l, the values of ml range from l, l-1... all the way to -l. ml values distinguish individual orbitals within a subshell of quantum number l. Thus, the significance of ml is that depending on how many values of ml ...

Jonathan Gong 2H

The effective nuclear charge is the net positive charge experienced by an electron through the pull of the positive nucleus. It is different than the nuclear charge because it takes into account the electron shielding effect which will lessen the net positive charge or full nuclear charge experience...

Jonathan Gong 2H

Yes. As Hund's rules states, electrons in the orbital are first filled up by m(spin) +1/2, meaning that in Nitrogen's case, they will all be pointing in the same direction if at ground state.

Jonathan Gong 2H

Intensity of light is measured as the rate at which energy is delivered to a unit of surface in terms of energy per unit time. EM energy is energy that is emitted from objects in the form of electrical and magnetic waves. Energy according to the equation E = hv, as well as c = lambda*v, depends on t...

Jonathan Gong 2H

The relationship between the intensity and frequency of light is that as frequency increases, intensity increases- so essentially, they are proportional. This is because intensity is generally gauged as the energy per some unit of time and according to the energy equation of light where E=hv, as fre...

Jonathan Gong 2H

For conversion into nanometers, you first need to solve for the wavelength of the violet light in meters. using the equation c=wavelength*frequency, you derive wavelength=c/frequency. Solving 2.998E8 m/s / 7.1E14 Hz gets you a wavelength of 4.2E-7 m. Since 1 meter is equal to 1E9 nanometers, you can...

Jonathan Gong 2H

I think it is true because when the wavelength increases, the slope of the EM radiation wave decreases, meaning the change of in an electrical field at a given point on the wave also decreases. Consequently, this means that there will be fewer complete oscillations passing through a point in a given...

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