CHEMISTRY COMMUNITY

Leo Naylor 2F

An increase in temperature causes the rate constant to increase as well, because reactants collide more often and thus form the products more often at higher temperatures.

Leo Naylor 2F

When K is between 10^-3 and 10³, we say that neither the products or the reactants are strongly favored. Although one side of the reaction may be slightly favored, K is not large or small enough to say that either the reactants or products are strongly favored.

Leo Naylor 2F

The salt bridge (||) is always placed between the anode and cathode. Commas are used to separate species in the same phase, while | is used to separate species in different phases. I have noticed that the order of species usually has the conducting solid on the outside, the compound closer in, and t...

Leo Naylor 2F

The left side of these diagrams (before the ||) is the anode, while the right side is the cathode. This means that the oxidation half-reaction involves the species on the left, while the reduction half-reaction involves the species on the right. Once you find the half-reactions, determine how many e...

Leo Naylor 2F

What he meant by this is that a second order reaction will always have two reactants (although it could be two of the same species) in the rate defining (slowest) step of a reaction, a first order reaction will always have one reactant in this step, etc. You can't conclude how many steps there are i...

Leo Naylor 2F

Catalysts are associated with zero-order reactions because the presence of a catalyst or enzyme can mean that the rate of the reaction is independent of the concentration of the reactant, since regardless of the concentration of the reactant, the catalyst/enzyme is working as fast as possible (const...

Leo Naylor 2F

Since initial concentration affects the half-life of the reaction, you know that the reaction is either second order or zero-order. You can determine which it is by plugging the given values into the equations t 1/2 =1/(k*[A] 0 ) and t 1/2 =[A] 0 /(2k) and finding which equation gives a consistent v...

Leo Naylor 2F

C_p is the heat capacity of a substance at constant pressure. Since it is used in the very important q=nCdeltaT, I would say that knowing about this property is very important for the final exam.

Leo Naylor 2F

I've really been enjoying Shitt's Creek on Netflix, it's hilarious, very well acted, and surprisingly wholesome at times!

Leo Naylor 2F

The order of a reaction is the sum of the exponents in the differential rate law equation, rate = [reactant1] n *[[reactant2] m . In other words, it is the sum of n and m, and if there are three reactants, it would be the sum of n, m, and l. The order of a reaction determines how the concentration o...

Leo Naylor 2F

A common mistake here is multiplying the reduction potential of each half-reaction by the coefficient in the chemical equation. Remember that E is an intensive property and does not depend on amount. To find E, just add 1.498 and 2.38 and plug this value for E into the equation. The value of n is 6.

Leo Naylor 2F

Q is equal to the partial pressure of the product (H₂) over the concentration of the reactant (H+) squared.

Leo Naylor 2F

This answer is exactly correct except that you used the wrong type of arrow, use the arrow that only points from reactants to products to indicate that this reaction is spontaneous in the forward direction. You can also realize to use this arrow because it is the same arrow as used in the skeletal r...

Leo Naylor 2F

Since the reaction takes place in a basic solution, instead of using H+ to balance the reaction, use OH- instead. I know Sapling says that you can pretend it is an acidic solution and then convert later, but I think that is more difficult than just using OH- immediately. Detailed instructions for ho...

Leo Naylor 2F

The main difference between the two equations is that the equation with ln can be used at any temperature, while the equation with log can only be used at standard temperature (25 degrees C). The fact that one equation uses log and the other uses ln is not important, although the log equation can ma...

Leo Naylor 2F

Notice that several of your terms, including Mn and Fe, do not balance out between the reactions. To solve this type of problem, first identify and balance each half-reaction separately, then combine them, making sure both charges and elements are balanced. Detailed instructions for solving this typ...

Leo Naylor 2F

Notice that the second form of the equation you listed does not have a temperature term, instead it assumes that the temperature is 25 degrees Celsius. Thus, this form of the equation can only be used when the reaction takes place at 25 degrees Celsius.

Leo Naylor 2F

Try selecting one of the other keyboards on the bottom and then you should be able to type in letters. If the "special" keyboard is selected you are unable to type letters.

Leo Naylor 2F

You are missing the O₂ molecule on the left that actually oxidizes ClO₂, and because of this your Cl terms are also unbalanced. Introduce the O₂ and you should be able to figure it out.

Leo Naylor 2F

Delta S nought is usually given in joules per Kelvin, and the properties are given in these units to avoid having to use scientific notation because of very large or small numbers for enthalpy and entropy.

Leo Naylor 2F

Another way to define residual entropy is that it ignores thermal entropy, because it is calculated only from the Boltzmann Formula.

Leo Naylor 2F

I know that 14C is listed as synchronous on MyUCLA, but I heard that it's actually asynchronous from a student who took it this year.

Leo Naylor 2F

You are using the correct equation. Make sure you convert kJ to J for the standard change in free energy and then convert back to kJ when inputting your answer. Also make sure your value for Q is (.65)²/(.45²*.25).

Leo Naylor 2F

The change in enthalpy is given by the heater, which produces 525 J per second (1 W = 1 J/s) or 525*5.65*60 J in 5.65 minutes. To find the molar enthalpy of vaporization, divide this change in enthalpy by the number of moles vaporized, which you can calculate from the molar mass of the substance and...

Leo Naylor 2F

Yes, you are correct that for fusion and vaporization, both the change in enthalpy and the change in entropy are positive. The same is true for sublimation (solid to gas) since it is simply the sum of fusion and vaporization. For the opposite processes, both the change in enthalpy and the change in ...

Leo Naylor 2F

How a temperature change affects the K of a reaction depends on whether the reaction is exothermic or endothermic. For an exothermic reaction, an increase in temperature will cause a shift towards the reactants. For an endothermic reaction, an increase in temperature will cause a shift towards the p...

Leo Naylor 2F

These two equations are just two ways of finding entropy. Which equation you use depends on the information given. If W of a material is given and you are only concerned with residual entropy, you would use the first equation. If the enthalpy of a reaction or heat entering or leaving the system as w...

Leo Naylor 2F

Sometimes. if doing heat capacity calculations, only the change in temperature is important, and so you don't have to convert because the change will be the same in either system. However, when working with entropy. you should convert to Kelvin because the value of entropy depends upon the temperatu...

Leo Naylor 2F

I would review material from Chem 14A as there were several weeks of content about how to draw molecules. In brief, you can use Lewis structures to represent the most stable state of a molecule, including its atoms, bonds, and lone pairs.

Leo Naylor 2F

K w is the equilibrium constant for autoprotolysis of water and represents the fact that the concentration of hydronium ions times the concentration of hydroxide ions will always equal 1.0 * 10 -14 . pK w is the negative log base 10 of K w , so yes, it always equals 14, whether a solution is basic o...

Leo Naylor 2F

Heat is the energy that is transferred between two objects or systems of different temperatures. Heat can also be defined as the energy associated with the random movements of atoms and molecules in matter.When we touch something hot, heat is transferred into our skin, burning us. The human body has...

Leo Naylor 2F

X can also be made negligible in quadratic equations, for example if you were solving for the [H] concentration of a solution and the K_a or K_b value is very small (less than 10^-3). Your equation would be x²/(conc_initial-x) = K_a, and you could simplify this to x²/(conc_initial) = K_a.

Leo Naylor 2F

Do not include liquids and solids because the molar concentrations of a pure solid or liquid will not change, so you don't need to include them.

Leo Naylor 2F

If the value given is molar heat capacity, you should convert to moles so that moles cancel out in the expression. If you are working with specific heat capacity, you should convert to grams (if needed) so that grams cancel out in the expression.

Leo Naylor 2F

This is a problem that I used to have a lot on multiple choice exams. My recommendation is that if you run into a problem that seems to be very mathematically involved, skip it and come back to it at the end. Ultimately, you will be able to answer more questions this way because you will be able to ...

Leo Naylor 2F

Pressure does not really affect liquids or solids because liquids and solids are essentially incompressible. So the answer to your question is no, a change in pressure will not affect a reaction as long as the reaction has the same number of moles of gas on both sides.

Leo Naylor 2F

The original solution is 100 times more concentrated than the diluted solution. You can use this information to find the pH of the original solution and the concentration of hydroxide from there. This information should also help you with part B by manipulating the concentration and using the molar ...

Leo Naylor 2F

In water, salts decompose into their constituent anions and cations. If one (and only one) of these parts is a strong acid or a strong base, the salt will act as a strong base or strong acid, respectively. If both the cation and the anion are a strong acid and a strong base, then the salt will be ne...

Leo Naylor 2F

Bases take H+ (protons) from the water surrounding them, turning some of the water into OH-. This is why bases increase the OH- concentration of a solution and thereby decrease the pOH.

Leo Naylor 2F

If K on the order of 10^-4 or smaller, it is safe to approximate that an expression like (0.22-2x)² is about (0.22)².

Leo Naylor 2F

K is just used as shorthand for K_c or K^p. K can be used interchangeably with K_c or K_p.

Leo Naylor 2F

Yes, you can use the ICE table to solve this. If the volume were not 1 L, as long as the partial pressure was given, you would not have to do an extra step. If for example moles were given, then you would have to divide moles by the volume to find moles per liter.

Leo Naylor 2F

If the concentration of something is decreasing, you should use a negative sign for x, and vise versa. For example, in a problem where you add one reactant into a vessel and the chemical reaction produces products, the sign for the reactant should be negative and the sign for the products should be ...

Leo Naylor 2F

Acids donate protons, while bases accept protons. You can often figure out whether a compound is an acid or a base by drawing its molecular structure. Some strong acids and bases you just need to memorize, however.

Leo Naylor 2F

If you added two equilibrium concentrations, the equilibrium constants would also be added together. However, most of the time when you modify existing equilibrium equations to find a new K value, you will multiply or divide the equilibrium equations because this allows you to remove terms from the ...

Leo Naylor 2F

Since all the reactants and products are gases, you should give the answer in terms of partial pressures. Also, if the values you are given are in terms of partial pressure, giving the answer in terms of partial pressure should be much easier since you will not have to convert between concentration ...

Leo Naylor 2F

Since water is present in large amounts in photosynthetic plant cells, the water is assumed to be in large excess for this reaction. Whenever a reactant is in large excess, you do not need to include it in the K value and thus changing the concentration of water will not affect the equilibrium compo...

Leo Naylor 2F

You have been given two values, the initial concentration of SO3 and the equilibrium concentration of SO2. Using these values, you can make an ICE table, solve for the x values using the given K value, and plug that x value back into the term for initial NO concentration. Good luck!

Leo Naylor 2F

All you should need to write the balanced equation is the chemical formulas of each of the gases. Writing the balanced equation is as simple as placing stoichiometric coefficients in front of each of the reactants and products. Hope this helps.

Leo Naylor 2F

If the problem simply says that there is an increase in pressure, you could assume that equal amounts (in moles) are being added to each of the gases in the equation. If you add equal amounts in moles to all the gases, there would be no change in equilibrium. However, "increase in pressure"...

Leo Naylor 2F

Yes, you do. However, this is not very helpful if you're simply repeating what everyone else has said, try to add at least one new thing (for example, another way of thinking about the problem) to your answer.

Leo Naylor 2F

You need to make a table. Write down the initial values that you are given and the equilibrium values that you are provided, then define the changes in concentration in terms of x, and finally plug all your equilibrium values into the equation and solve for x.

Leo Naylor 2F

Another condition given in an equilibrium problem might be the volume of the container, so remember to divide given moles by volume before you start the problem.

Leo Naylor 2F

In math, proportional equations mean that the equation is equal except for a constant missing from one or both sides. Adding a constant changes the equation from a proportional equation to an real equation, i.e., the two sides are equal.

Leo Naylor 2F

You forgot to divide the moles by the volume of the container, so the correct value of x is four times smaller than the one you found (x=0.035). Hope this helps!

Leo Naylor 2F

To answer this question in another way, removing the product would reduce the Q_c of the reaction, since the concentration of product will decrease. Now that Q is lower than K, the reaction will move in the forward direction until Q = K once again and chemical equilibrium is restored.

Leo Naylor 2F

I want to develop my communication and scheduling skills, as these things are a lot more difficult in the era of COVID and as a college student.

Leo Naylor 2F

I want to develop my communication and scheduling skills, as these things are a lot more difficult in the era of COVID and as a college student.

Leo Naylor 2F

Just to add to your answer, the non-hybrid 2p orbitals also play a part in bonding in this molecule, forming the second (pi) bond between each oxygen and the carbon.

Leo Naylor 2F

The original poster mentioned not using trial and error, so in order to save time, while drawing the structure try to make sure that the formal charges are as close to zero as possible. In order to achieve this, you can follow trends like nitrogen forming three bonds, oxygen forming two bonds, and f...

Leo Naylor 2F

I agree with lots of people that listening to music without lyrics can make studying very easy! My favorite album to listen to while studying is Raise Your Skinny Fists Like Antennas to Heaven by Godspeed You! Black Emperor. It won't be for everyone but I find it so conducive to focus.

Leo Naylor 2F

Interesting question. I generally don't use mosquito spray because of the chemicals in it, but I don't think said chemicals are very dangerous to humans in the amount they're present in bug spray. Also, in areas where mosquitos carry diseases like malaria, mosquito spray is definitely justified and ...

Leo Naylor 2F

I am planning to play lots of video games while I have time!

Leo Naylor 2F

The COOH group gives away a proton in the form of a positively charged hydrogen atom, which makes it an acid.

Leo Naylor 2F

You are correct, coordination number is just the number of bonds from the central atom to ligands.

Leo Naylor 2F

You can usually tell by the chemical formula of a coordination compound what the oxidation number of the metal cation is. For example, in the coordination compound [Co(NH 3 ) 4 Cl 2 ]Cl, you can see that there are three chlorines, each with an oxidation number of -1. Since the compound is neutral ov...

Leo Naylor 2F

The oxidation state is the positive charge of the metal atom, so oxidation state + oxidation states of other atoms in the compound must equal overall charge of the compound. Since this compound has an overall charge of -1, and each chlorine atom has an oxidation state of -1, the oxidation state of c...

Leo Naylor 2F

The oxidation state is +2 because the overall charge of the molecule is neutral, and you know each chlorine atom has a charge of -1, so since there are two chlorine atoms, the charge of the cobalt must be +2 to result in a neutrally charged molecule.

Leo Naylor 2F

The name is composed of ligands in alphabetical order with greek number prefixes, then the name of the transition metal, then any atoms outside. So this molecule would be tetramminecholocobalt (III) dichloride.

Leo Naylor 2F

Bromide specifically refers to Br-, Br₃ is named tribromide.

Leo Naylor 2F

To exlplain further, a coordination number of six means there are six bonds between the transition metal and the ligand. Six bonds arrange themselves in an octahedral geometry with four ligands in the plane at 90 degrees and one ligand above and below the plane.

Leo Naylor 2F

You just need to replace hydro with aqua, as indicated on the ligand naming sheet from discussion. Since aqua starts with an a and there is only one water molecule, the molecule begins with "aqua" and then the rest of the name follows.

Leo Naylor 2F

Pi bonds cannot rotate because they are p-orbitals overlapping side-by-side, so that both electron density areas are "touching." Hope this helps.

Leo Naylor 2F

Since As is in the 4th period of the periodic table, it can use d-orbitals to form an expanded octet. Any elements with atomic number > 20 can use d-orbitals to form an expanded octet.

Leo Naylor 2F

Jaden Haskins 2F wrote:What is the reason that p-block elements can have an expanded valence shell? Why do elements with an atomic number >20 want more electrons?

These elements can have an expanded valence shell because they can use d-orbitals for bonding, meaning they can have more than an octet of electrons.

Leo Naylor 2F

I think that the professor mentioned that most transition metals are more stable with an expanded octet, just like some p-block elements. Additionally, the transition metal had an expanded octet in each example he provided.

Leo Naylor 2F

No, I don't think either of these concepts are mentioned in any of the lectures.

Leo Naylor 2F

The negative poles are located closer to the more electronegative atom in the compound, since that atom attracts electrons more strongly. For example, in H₂O, the negative pole is located closer to the oxygen than the hydrogens.

Leo Naylor 2F

Yes, I believe that all Lewis bases are ligands and vise versa because both definitions define a compound that can give away two electrons to form a coordinate bond.

Leo Naylor 2F

Yes, a molecule like O₂ has both lone pairs and is linear. However, a molecule with three atoms would not be linear if the central atom had any lone pairs.

Leo Naylor 2F

The number 3 comes from the fact that there are three separate p-orbitals used to form the sp³ hybridization,

Leo Naylor 2F

The first bond between any two atoms will always be a sigma-bond, while the second and third bonds between the atoms (in a double or triple bond) will be pi-bonds. You should be able to figure out which atoms have single, double, and triple bonds from the Lewis structure and then use that informatio...

Leo Naylor 2F

During exams, we will always be provided with the molecular formula for a compound when determining its shape in addition to the name of the compound. Thus, I think it would be reasonable to look up the formulas of these molecules.

Leo Naylor 2F

I think that VSEPR formula refers to finding the placement of lone pairs and paired electrons and using that information to determine the overall shape of the molecule.

Leo Naylor 2F

I think that the shape of an ion depends on the location of its unpaired electron, which affect its regions of electron density and therefore its shape. The bond angle of OClO would be affected by the lone pairs on the chlorine atom, giving the molecule a "bent" shape.

Leo Naylor 2F

Dr. Lavelle stated in the lecture that both types of dipole intramolecular forces have an energy of -2kJ/mol. I agree that dipole-dipole seem intuitively stronger, but I believe they are the same.

Leo Naylor 2F

I believe that the concept of formal charges only applies to covalent bonds. I wrote in my notes that the definition of formal charge is "gain or loss of electrons of an atom when forming a covalent bond." Thus, formal charge does not apply to ionic compounds. This also makes sense because...

Leo Naylor 2F

To further clarify, "dipole" is a characteristic of a covalent bond in which electrons are unequally shared, so one atom is slightly positive and the other atoms is slightly negative (hence the name). Ionic bonds form when a cation "gives" an electron to an anion, creating one fu...

Leo Naylor 2F

Also, each lone pair on an atom like nitrogen can form a hydrogen bond, as long as you ignore that the space might not be enough for two water molecules. Thus, the answer might be more than you originally thought. Hope this helps!

Leo Naylor 2F

This molecule has no hydrogen bonded to a highly electronegative atom, so it cannot form hydrogen bonds. It could form hydrogen bonds with water because of the oxygen bonded to the carbon, but it cannot make hydrogen bonds with itself.

Leo Naylor 2F

Nitrogen has the lowest ionization energy of the elements listed, so it would be the central atom in the Lewis structure. I think that this is a more important consideration than formal charge.

Leo Naylor 2F

As far as I know, orbitals are math functions which represent the likelihood of an electron being at any given point at any given time. They are math functions because they are three dimensional sine waves.

Leo Naylor 2F

Electrons have unique quantum numbers, meaning no two electrons can exist in an atom with the same quantum numbers. Within each suborbital, the first three quantum numbers are the same, meaning the fourth quantum number can either be -1/2 or 1/2. Thus, one "spin down" electron and one &quo...

Leo Naylor 2F

To clarify further, formal charge is defined as the gain or loss of electrons of an atom when forming a covalent bond. Thus, an atom not forming a covalent bond could not have a formal charge.

Leo Naylor 2F

Hydrogen could not donate an electron pair because it only has one electron in its base state. Helium theoretically could donate an electron pair, but would not because both of its electrons are tightly held, explaining helium's non-reactive nature. Lithium only gives up one electron when forming an...

Leo Naylor 2F

Rohit, as far as I can tell your answer is mostly correct but (a) also does not follow Hund's rule.

Leo Naylor 2F

Remember, a ground state atom will follow Hund's rule. That is, electrons will fill a subshell by first occupying different orbitals with parallel spin and then filling in these orbitals only when more electrons are added. So the C electron configuration shown here is not the ground state. Also reme...

Leo Naylor 2F

At energy level n=2, an atom could have the s and p states. Therefore, there could be two atoms in the 2s state, and six atoms in the 2p state. In total, this atom could have eight electrons. This is represented on the periodic table, as Neon is the atom with the highest number of electrons (8) cont...

Leo Naylor 2F

The reason that 4s comes before 3d for K and Ca is that the 4s state has a lower energy level than the 3d state for these specific elements. In elements like scandium, the 3d state is once again a lower energy so 3d is written before 4s. Basically, K and Ca are exceptions. Hope this helps.

Leo Naylor 2F

O2- is slightly larger than F- because despite having the same number of electrons, O2- has a smaller nuclear charge and thus attracts the electrons less strongly than F-.

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