CHEMISTRY COMMUNITY

azurexrose

Bond enthalpies are always positive because it takes energy to break a bond, so it's kind of like an endergonic process.

azurexrose

Bond enthalpies are always positive because it takes energy to break a bond.

azurexrose

Different orders of reactions have different variables to put on the axes to make the graph a straight line. For example, to get a slope of -k in a zeroth order reaction you just have the x axis be time and y axis be concentration of reactant. In a first order reaction, to get a slope of -k, the x a...

azurexrose

The catalysts usually change the mechanism of the reaction in a way that it takes lower activation energy and therefore increases k, speeding up the reaction.

azurexrose

You can use k to solve for the activation energy using the Arrhenius equation, if k increases, activation energy decreases and vice versa.

azurexrose

You find the overall order by combining the order of each individual reactant and adding them together.

azurexrose

The reaction rate is dependent on the slow step because the fast steps are assumed to be so fast they they quickly become the products or shift to equilibrium that it will not reasonably affect how quickly the reaction goes.

azurexrose

k is negative in any calculations solving for concentration of reactants after some time because the reactants are decreasing in concentration due to becoming products.

azurexrose

You look at the reduction potentials of the half reactions given to you and find it by doing E˚=Ecathode - Eanode. Usually which ever substance is acting as the cathode and anode is given to you but if not the one with a lower reduction potential usually acts as the anode.

azurexrose

An isothermal process means that temperature is constant throughout while an isometric process means that volume does not change, meaning work is 0.

azurexrose

The overall equation is U = q + w, but you need to look at whether the work done is positive or negative.

azurexrose

Calorimeters basically measure how much energy is released or absorbed during a reaction by looking at the change in temperature. You can then use the calorimeter constant to use the change temperature to calculate change in heat.

azurexrose

An amphoteric substance is one that can act as both an acid and a base, while an amphiprotic substance is one that can both accept and donate electrons. Often times compounds are both amphiprotic and amphoteric, and all amphiprotic compounds are amphoteric. But not all compounds that are amphoteric ...

azurexrose

∆G˚ represents the change in Gibbs free energy under standard conditions, AKA at equilibrium constant K and also when T = 298 K. ∆G is used to find the change in Gibbs free energy under different conditions and when a reversible reaction is not at equilibrium.

azurexrose

I'm glad I felt like my studying paid off this year :)). Thank you for asking, and I hope you had a great quarter.

azurexrose

(d[P])/dt is the instantaneous rate, the rate at that moment, that the product is being formed.

azurexrose

Delta G is change in Gibbs free energy. A positive Delta G means the reaction is not spontaneous while a negative Delta G means the reaction is spontaneous. Delta G is calculated through either Delta H - T*Delta S or through -RTln(K).

azurexrose

k is the reaction constant for the forward reaction, while k' is the reaction constant for the reverse reaction. k/k' makes big K, the equilibrium constant.

azurexrose

Catalysts will be seen in the beginning of the reactants and come out at the end of the products unchanged. Intermediates are just an intermediate state that the atoms go in that is not seen in the beginning or the end, as they come from the reactants and become the products.

azurexrose

Yes, the reducing agent is the anode while the oxidizing agent is the cathode. I generally just think of it as the reverse of what's happening to it, the thing getting oxidized is the reducing agent and the thing getting reduced is the oxidizing agent.

azurexrose

K is the equilibrium constant, or the concentrations of reactants and products that a reaction tends to under certain conditions. Q is the reaction quotient, or the ratio of reactants and products at the current moment. You can look at which is bigger, Q or K, to determine where a reaction that is n...

azurexrose

The easiest way is to determine the order of reaction, whether it's 0th, 1st, or 2nd, and use the integrated rate law for that specific order.

azurexrose

I saw this online, but the reverse of the Haber process (where ammonia is produced from H2 and N2), or the decomposition of ammonia, is a zero order reaction.

azurexrose

The rate is sort of like measuring speed in how it quickly it is going through. But the concentration of reactants specifically is negative because the reactants are becoming products.

azurexrose

You calculate the concentration of an ion after it breaks up from the rest of a salt using the K value and ice tables, then divide by the original concentration of the salt.

azurexrose

n represents the number of electrons being transferred. If the charge of an ion causing a voltage difference is +1, then n will be 1, and so on.

azurexrose

According to the Arrhenius equation, temperature and activation energy are the only two factors that affect rate constant k. However the overall rate reaction still depends on the concentration of the reactants also also the order of reaction that reactant is.

azurexrose

k1 is the first reaction, k2 is the second, and k’ represents the reaction constant of the reverse reaction.

azurexrose

The anode goes through oxidation and is typically the side with lower electric potential. It also is the side that loses mass because the solid used gets oxidized and becomes aqueous. The cathode goes through reduction and typically is the side with higher electric potential. It gains mass because d...

azurexrose

You can have as many products and reactants as you want but the method of finding reaction order will still be the same.

azurexrose

Yes, there are some elements that can have both + and - oxidation numbers. For example, N2H4 has the N with an oxidation of -2 while in NO2 it has oxidation number +4.

azurexrose

In a redox reaction, often the oxygens or hydrogens will not balance out. You need to add either H+ or H2O to balance out the reaction if it’s in an acidic solution, while you need to add either OH- or H2O to balance out the reaction if it’s in a basic solution.

azurexrose

Since the reaction is 0th order, you just use the equation [A] = -kt+ [A]0. Plug the values given to you and solve for t :))

azurexrose

Overall reaction order lets you determine which units to use for k and also how the reaction will looked while graphed.

azurexrose

The first one is used for temperatures not at 298K while the second one already has the RT/F solved for you since it’s supposed to be used at 298K.

azurexrose

If temperature is increasing and the reaction is endothermic, then it’ll favor the production of the products, and vice versa for if the reaction is exothermic. If temperature is decreasing and the reaction is endothermic, it’ll favor the production of reactants and vice versa for exothermic.

azurexrose

If temperature is increasing and the reaction is endothermic, then it’ll favor the production of the products, and vice versa for if the reaction is exothermic. If temperature is decreasing and the reaction is endothermic, it’ll favor the production of reactants and vice versa for exothermic.

azurexrose

When H2O is a liquid, it’s acting as a solvent, and you don’t include it in the rate law.

azurexrose

Thank you Mr. Lavelle!!
I really appreciate how much time and energy you put into giving your students as much help as they need. :))

azurexrose

H and G convey different information, H represents whether a reaction gives off or absorbs energy, G represents whether or not it is spontaneous.

azurexrose

A greater Q than K means that it has a higher concentration of products than at equilibrium, so the reaction will move to the reactants side to get to equilibrium, and vice versa.

azurexrose

Like with pH, pKa just means taking the negative log of the Ka to get value between 0-14.

azurexrose

Like with pH, pKa just means taking the negative log of the Ka to get value between 0-14.

azurexrose

Yea, I think he just uses it as a common biological example of something involved in an exergonic reaction, like cellular respiration and combustion.

azurexrose

Yea, I think he just uses it as a common biological example of something involved in an exergonic reaction, like cellular respiration and combustion.

azurexrose

You usually use this equation in irreversible compressions and in compressions against a constant pressure.

azurexrose

You usually use this equation in irreversible compressions and in compressions against a constant pressure.

azurexrose

I would usually just start by plugging ones into the concentrations. So then it would look like
0.29[1][1]^2. =
Then you just double or half or whatever the problem asks, so if A is halved and B is tripled u just plug it in and relate it to the original value.

azurexrose

A state function is a characteristic that means that it doesn’t matter which path is taken, the final and initial values will always been the same. Gibbs free energy is a state function because it is defined by other state functions, such as Delta H and Delta S.

azurexrose

You pretty much will always be given what the fast and slow reactions are.

azurexrose

Hello, I don't know how to calculate how much work is done by the irreversible reaction in part c. Suppose you have a sample of an ideal gas in a 9.00 L piston at 843 K and 0.351 atm. (a) Calculate the work done if the gas is expanded to 27.0 L by a isothermal, reversible process. (b) What is the ch...

azurexrose

I don't think so, It can't realy act as an acid.

azurexrose

If there are multiple lone pairs arranged in a way where you could see them bonded to a central ion at multiple points, then it is probably polydentate. There are also some ligands that you can memorize, like (en), (dien), and (ox).

azurexrose

No, you need to have at least two orbitals to make a hybrid orbital.

azurexrose

In molecules with isomers, there are similar atoms, like two Cl molecules, bonded to a central atom. In cis isomers, the similar atoms are on the same side. In trans isomers, the similar atoms are on opposite sides.

azurexrose

It basically means how much energy it takes to turn one mole of a compound into a gas.

azurexrose

The 25˚C in this situation is just indicating that the solution is at standard conditions.

azurexrose

You can divide 1*10^-14 by the known concentration of either OH- or H+ to get the concentration of the other.

azurexrose

Electronegativity refers to how much an atom pulls electrons towards it when in a covalent bond. Electron affinity is how much energy is released by an atom when an electron is added to it.

azurexrose

Since weak acids have a certain pKa, when conjugate bases such as F- are in water, some of them will bind to H+ ions in the water to make HF, therefore lowering the H+ concentration and increasing pH. This is a similar process for conjugate acids, such as if an NH4+ ion dissolves in water, releasing...

azurexrose

They will usually bind with water to make an acid, for example, CO2 binds with H2O to make H2CO3, which is carbonic acid. SO3 will bind with H2O to make H2SO4

azurexrose

No, hydrogen bonds will not be stronger than any covalent bonds.

azurexrose

One easy thing to look at is the set of acids and bases that are in the same group, for example the HCl HBr and HI, and NaOH, LiOH, KOH, etc. The higher the period, the stronger the acid or base will be, as in HI > HBr > HCl, because the larger the atom, the longer the bond between the ions, and the...

azurexrose

I think these jokes are sodium funny. In fact, I slapped my neon that one!

azurexrose

Good luck on the rest of your finals guys!! I know you guys can do this!!

azurexrose

A cis isomer means that similar atoms or groups are on the same side as each other. A trans isomer means that the similar atoms or groups are on opposite sides of each other.

azurexrose

Li+ and Br- are both part strong bases and strong acids respectively, LiOH and HBr. The conjugate bases of strong acids are very weak, and the conjugate acids of strong bases are also weak. This will mean that the Br- and Li+ will have no effect on the pH, and LiBr is therefore a neutral salt.

azurexrose

The concentrations of OH- and H+ (or H3O+) are always inversely proportional, and always multiply to be 1 x 10^-14. So that means that an OH- concentration of 1 x 10-7 means an H+ concentration of 1 x 10^-7 (this is neutral), and an OH- concentration of 1 x 10^-8 means an H+ concentration of 1 x 10^...

azurexrose

When a ligand forms a chelate, it basically means that it binds to the central metal ion at more than one point, and therefore makes a ring. This means all polydentate ligands are chelating.

azurexrose

The lower the pH, the more acidic. So strong acids will have lower pH.

azurexrose

This happens to be a coincidence in this case just because Br- has a charge of only -1, so you need three to counteract a charge of +3 on the positive ion. If the ion were not -1, then you would need a different coefficient for the number outside the bracket; for example if the charge of the complex...

azurexrose

I just had boba!! Is there a chemical reason why sometimes the boba pearls are hard and sometimes they are softer?

azurexrose

I believe how this works is that to determine the position of an electron, you need to be able to see it with light, basically it needs to hit the electron and bounce off. However, the photon hitting the electron will change the direction and speed of the electron, therefore changing its velocity.

azurexrose

The dissociation of each individual proton has its own pKa, so how much the dissociation of each proton affects the pH of a solution just depends on how much of the acid or base there already is in the solution

azurexrose

I believe for your second questions that for acids and bases without OH- and H+, you kinda just have to memorize that they are acids/bases.

azurexrose

Yes, the ligands in cisplatin are chlorine and NH3

azurexrose

The easiest oxidation numbers to solve for are when you have either a free element or an ionic compound, in that case the oxidation number is 0 and the original charge of the ion respectively. Oxidation numbers are based off of assuming that electrons in a bond go to the more electronegative atom in...

azurexrose

A formal charge is the charge of an individual atom in a molecule if all the electrons in bonds are assumed to be shared equally (basically meaning if electronegativity were not a thing). This is why lone pairs count as two atoms while bonds count as one atom when calculating formal charge. All atom...

azurexrose

Like the replies above me have stated, they really don't have any effects on the IMF in the atom. They are just used to determine the stability. For example, even though the presence of fluorine in a molecule may indicate that hydrogen bonding and dipole-dipole interactions happen, fluorine will pre...

azurexrose

Generally, the more lone pairs and bonds an atom has, the smaller the angle. Look for the atom that has the most bonds and lone pairs on it and use that to determine the smallest bond angle. If the most bonds and lone pairs an atom has is 6, then the angle is 90˚, if it's 5 then it is also 90˚, with...

azurexrose

Cis-dichloroethane has the two chlorine atoms on the same side of their respective carbon atoms, kind of like Cl Cl C C H H Therefore, there's a dipole moment on the Cl side because it's a lot more electronegative than carbon and they aren't orientated in a way that they cancel each other out. There...

azurexrose

I don't use the textbook for reading, but I think the practice questions at the end really help on math questions during midterms.

azurexrose

Cl is closer to fluorine, the most electronegative element, than Be, so Cl is more electronegative.

azurexrose

You also need to factor in the positions of nonpolar or polar bonds, for example, CHF3 is polar despite its tetrahedral shape because the distribution of polar and nonpolar bonds are asymmetric

azurexrose

Also, I would like to add that if you assume the central atom has a formal charge of 0, the atom must want 5 valence electrons, but can't be nitrogen (due to there being more than an octet). This would also lead you to concluding phosphorus were correct.

azurexrose

I think so, but I'm not sure. wikipedia says yes, but based on what we learned in class I don't really know

azurexrose

As far as I've learned, they've been interchangable with each other.

azurexrose

Here's the process I generally use. First I look at the polarities (through the Lewis structures like Raymond said). If both are nonpolar, the larger molecule will have stronger LDF and therefore have a higher boiling point. If one is not completely nonpolar and the other is nonpolar, unless there i...

azurexrose

I kind of like to remember this as the opposite of what we think of acids. Acids usually donate protons, and the opposite of that is accepting electrons. Therefore, lewis acids accept electrons. Normal bases accept protons, the opposite of that is donating electrons, so lewis bases donate electrons.

azurexrose

It represents lone pairs on the central atom only.

azurexrose

Across a period, the electronegativity increases across a period while it decreases going down a group. It has little to do atomic radiua

azurexrose

The boiling point of ionic compounds like NaF or KCl is determined by the strength of attraction between the ions, which can be found by looking at the difference in electronegativities. Ionic compounds aren't really grouped in separate molecules like covalently bonded molecules are, so there aren't...

azurexrose

Generally, yes.

azurexrose

You first look at whether an atom is polar or nonpolar. If both molecules you are comparing are nonpolar, then the molecule with a larger electron cloud (more/heavier atoms) will have higher polarizability and therefore stronger LDFs, so that molecule has a higher boiling point. If one is polar and ...

azurexrose

I think I remember that part of the slide meaning that unless the energy of the photon is greater or equal to the energy required to remove the electron, then the equation will not apply and no electron will be removed.

azurexrose

Each photon has its own individual energy that you can get from using E = hv. If you need to find the total energy required, you can divide it by the individual energy of a photon to find how many photons are needed. Similarly, if you need to get the energy from a group of photons of the same freque...

azurexrose

The electron would have the longer wavelength. If you plug in the mass and velocity to get the momentum for both and divide plank's constant by both their momentums, you will get a larger value for the electron than the proton, so it has a longer wavelength wavelength = h/(mv) Proton: 6.626*10^-34/(...

azurexrose

Hi, so for this question, we didn't need to know the frequency of the microwave before. We just needed to first calculate the wavelength that it would take to remove an electron given the work function, and then we take the new information that we're given in part 2 (that the microwave gives off wav...

azurexrose

I'm fairly sure that I've never used farenheit on a high school chem question, so I'm gonna assume the same here as well. I think generally Kelvin and Celsius are the only ones you use, though more Kelvin than Celsius.

azurexrose

The molar mass of tristearin is 891.48 g/mol. Since we have 454 g of tristearin, this means there's 0.509 moles of it. Since 2 moles of tristearin produces 110 moles of water, 0.509 moles should produce 28.01 moles of water. Since the molar weight of water is 18.02, 28.01 moles of water would weigh ...

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