CHEMISTRY COMMUNITY

Isabelle Huerta 2I

Nope! Catalysts will not be consumed in the reaction. Catalysts are for facilitating the reaction and provide an alt pathway w/ lower activation energy so it increases the rate of reaction without actually being consumed. When the reaction is complete, catalysts are recovered (uncharged) and can be ...

Isabelle Huerta 2I

Hi! For this problem you can use the relationship between Eº cell and ∆Gº with the equation ∆Gº = -nF Eº cell (n = num of moles transferred, F = Faraday constant). First you'd calculate the num of moles of electrons being transferred using stoichiometry and the balanced equation. Then, with the give...

Isabelle Huerta 2I

It would be safer to assume no! Entropy does not have to equal zero because abs tempt = 0K. The third law of thermo tells us that entropy of a pure substance approaches zero and the temp approaches zero, but it doesn't mean that entropy = 0 for ALL substances. In terms of ideal substances though, th...

Isabelle Huerta 2I

In setting up an ICE table using pressures, the process is similar just changing the units! Write down the initial PRESSURES involved in the reaction. Then determine how it is changing for the species and make sure to take into account the stoichiometric coefficients of the balanced equation (make s...

Isabelle Huerta 2I

Hi, no it doesn't! A higher pKa value will mean that we have a weaker acid/stronger conjugate base. The pKa value is going to be the -log(Ka) ((Ka being the acid dissociation constant)) and it will measure the strength of the acid. A higher pKa value is an indicator that the acid is less likely to d...

Isabelle Huerta 2I

Yes!...but it depends. Second order reactions can be faster/slower than first/zero order reactions depending on the reaction kinetics and the conditions. Usually second order reactions involve the simultaneous collision of 2 reactant molecules and move faster than first order reactions (have collisi...

Isabelle Huerta 2I

A way to remember which equations are applied to which isothermal reactions, we focus on identifying the specific conditions of each equation. Equations that have terms "isothermal" "constant temp" or "T = constant" will apply to reactions with constant temp.

Isabelle Huerta 2I

When determining if half-reactions involve different amounts of transferred electrons, we have to examine the change in oxidation states for reactants and products. We have to look for discrepancies in the num of electrons gained/lost by each species. If there are any discrepancies, then the half-re...

Isabelle Huerta 2I

We use oxidation numbers when balancing redox equations because it helps us to track the transfer of electrons from reactants and products. We assign oxidation numbers to allow us the identification of elements that are oxidized (lost electrons) and which got reduced (gained electrons) during any re...

Isabelle Huerta 2I

Yes, you're right! For cell diagram notations, a comma (,) will be used when separate different species that are in the SAME phase. The vertical line (|) is only used to separate species that are in DIFFERENT phases. This makes it easy to distinguish between compounds of the electrochemical cells.

Isabelle Huerta 2I

So when we are analyzing percentage deprotonation, we need to know that it is to indicate the proportion of acid molecules that donated a proton in the solution. Now we have an insight on the strength of the acid. The higher percentage of deprotonation will mean we have a stronger acid and greater d...

Isabelle Huerta 2I

When we are assigning oxidation numbers to these chemical reactions, we should not be considering the coefficients. We need to focus more on the atoms individually that are in the compounds involved. So for the reaction 2Na + Cl2 --> 2NaCl, the two Na atoms will have an oxidation state of +1 and the...

Isabelle Huerta 2I

You have to add Pb to a cell diagram when Pb is involved in the electrode reaction. It can even just act as an electrode in the electrochemical cell. If the cell reaction has reduction/oxidation of lead, or lead being one of the electrodes, then it needs to be included in the cell diagram. If it isn...

Isabelle Huerta 2I

To know whether a metal will dissociate is dependent on the standard reduction potential (Eº). Metals that have a positive Eº will stay as solid metal in a solution. Metals that have a negative Eº will dissociate into their respective ions. To be able to determine whether you need to include free fl...

Isabelle Huerta 2I

Hi! Some other ones that will come in handy are Watts (W) for Power and Joules(J) for Energy. I hope this helped :)

Isabelle Huerta 2I

Temperature has the ability to influence cell potential by the Nernst equation. Nernst equation states that as temperature rises, cell potential increases (endothermic reactions) or decreases (exothermic reactions). Temperature will affect the entropy change of a reaction and the balance between ent...

Isabelle Huerta 2I

Yes, some catalysts definitely work better than others. This can be due to surface area, specificity, or strength with reactants. For example, enzymes are efficient catalysts and specific to substrates (some, not all), so they provide greater reduction in activation energy than heterogeneous catalys...

Isabelle Huerta 2I

Galvanic cells are those that generate electrical energy (spontaneous reactions), can convert chemical energy -> electrical energy (redox reactions). Electrolytic cells will use electrical energy for non-spontaneous reactions, and convert electrical energy -> chemical energy. These cells force react...

Isabelle Huerta 2I

The rate law of a reaction is the relationship of the rate of a reaction and the reactants concentrations. The rate law is expressed as rate = k[A]^x [B]^y (k = rate constant, x/y = reaction orders dependent on reactants A/B). The reaction order can range from zero, first, second, and so forth -- an...

Isabelle Huerta 2I

Molecules that are in the transition state mean to have reached an unstable, high-energy state. Molecules in transition state are dealing with the rearrangement of chemical bonds so they are possessing partial traits of the reactants and of the products. They also have a very high energy during the ...

Isabelle Huerta 2I

∆G (Gibbs free energy) and K (equilibrium constant) relationship is shown in the equation ∆G = - RT ln(K) -- (R = gas constant, T = temperature in Kelvin). So if ∆G is negative then the reaction is spontaneous. A spontaneous reaction will favor an increase in products at equilibrium to compensate fo...

Isabelle Huerta 2I

Reaction mechanisms help to explain the kinetics of complex reactions by providing us a step-by-step explanation of reactants transforming into products. With this we can identify the rate-determining step, and the reaction mechanisms offer insight to kinetics of reactions. We can determine the reac...

Isabelle Huerta 2I

We can tell the difference by taking note of the solution that we are working with. In acidic solutions, x will usually represent the concentration of H+ ions. In a basic solution, x will typically be referring to OH- ions. So the identity of x will depend on the type of solution and reaction that i...

Isabelle Huerta 2I

We start by calculating the concentration of the OH- ions that form from the reaction. Given that this is a basic reaction, we can find pOH by calculating the negative log of [OH-]. We then have minus this value from 14 to find the pH (pH + pOH = 14) and the pH would be 6.6.

Isabelle Huerta 2I

Le Chatelier's Principle is used to predict when the concentration of an acid or a base has been altered, and what direction equilibrium will shift to counteract it. So if more HCl is added to a solution with Cl- as its conjugate base, then Le Chatelier's will suggest the equilibrium shifts to the r...

Isabelle Huerta 2I

Anions will affect the pH, but can do so in different ways. They can either contribute OH- ions or affect the equilibrium of the water. Basic anions or weak bases that dissociate can definitely increase pH by adding in OH- ions to the reaction. But the acidic anions react with water and this will ha...

Isabelle Huerta 2I

So when pressure is changing, both the forward and reverse rates will adjust non-linearly whether they increase or decrease. Eventually they will come together as the same value when equilibrium is reached, but one rate is going to remain higher than the other (this depends on the conditions of the ...

Isabelle Huerta 2I

Equilibrium constants should be applied when dealing with ATP hydrolysis since we are balancing between ATP and ADP (products of hydrolysis). The equilibrium constant (K) is going to represent the ratio of the concentration of the products and the reactions when they are at equilibrium. The enzymes ...

Isabelle Huerta 2I

In order to be able to determine the final temp of ice mixed with water, you have to combine heat absorbed from melting ice (q = m_ice * ∆H_fus) and heat absorbed from warming the ice and water (q = mC∆T). We have to find the total heat absorbed by the ice and the total heat released by the water wh...

Isabelle Huerta 2I

I believe it means the same when the question refers to ionization/protonization when concerning weak acids/bases, the concept is the same but it is different in what it is in reference to (acids or bases). It is simply about the transfer of H+ ions from an acid or base molecule to water. Weak acids...

Isabelle Huerta 2I

For problems working with a bomb calorimeter, it usually means that we are focusing on the heat being released/absorbed with volume at a continuous rate. The bomb calorimeter is referring to a sealed container where the reaction is occurring at a constant volume. A bomb calorimeter is able to measur...

Isabelle Huerta 2I

The way that temperature affects enthalpy change is by playing a role in the energy levels of the reactions and the products. Increasing temperature will typically have a favor over endothermic reactions because it will result in more thermal energy proceeding the reaction. Exothermic reactions are ...

Isabelle Huerta 2I

The main thing when determining the difference between ∆H and ∆U is what they're looking for and what they bring to the system's energy. ∆H is referring to the heat that is being transferred in/out of a system when pressure is a constant (∆P = 0). This value takes into account the internal energy an...

Isabelle Huerta 2I

No we do not always have to add Pt(s) because they are only there when we are lacking a solid compound in the electrochemical reaction. When this happens, the Pt(s) is what provides the surface for electrons to be transferred throughout the reaction. When solid compounds are present in the reaction,...

Isabelle Huerta 2I

Yes, there are times where a phase change is reversible. We have to take into account the rate that it cools/heats because it can play a role in its ability to be reversible. Cooling/heating at a slower rate than most will take the phase change longer to reach equilibrium so there is more mobility t...

Isabelle Huerta 2I

Reactions are capable of having more than one catalyst. Some scenarios that I know of where this happens is: (1) there are multiple steps happening within the reactions, (2) the multiple catalysts are there to enhance their activity, and (3) the need for more than one catalyst is linked to the condi...

Isabelle Huerta 2I

Hello, I was looking over my notes and was confused on the section about the ICE box. In the 'change in conc' column, some initial conc are being subtracted/added by 2X and one is subtracted by X. Why is the '2' there and how do we know it's supposed to be there for future reference? Thank you.

Isabelle Huerta 2I

When the total pressure increases then it could mean (1) the reaction is creating more gas as a product, (2) the reaction is exothermic, (3) or the volume of the chamber had decreased.

Isabelle Huerta 2I

So in an exothermic reaction, the temperature would act as if a product was being added to the reaction. Meaning that the goal would be to counteract this by decreasing the concentration of products and ergo decreasing K. Whereas, in an endothermic reaction, there are more reactants being added to t...

Isabelle Huerta 2I

The equation I have written down is PV=nRT but I'm having trouble placing the "n" and "T". What do they represent for this equation? Thanks.

Isabelle Huerta 2I

Leading Zeros are used to indicate the scale or magnitude of a number but don't add to the precision of the measurement. Zeros between nonzero digits are considered significant because they indicate precision or accuracy in the measurement. Tailing zeros in a number without a decimal point may or ma...

Isabelle Huerta 2I

Nonpolar Covalent Bond: This occurs when the electronegativity difference between two atoms is very small or nonexistent. Generally, a difference of less than 0.5 in electronegativity is considered indicative of a nonpolar covalent bond. In these cases, the shared electrons are evenly distributed be...

Isabelle Huerta 2I

Sulfur, in its bonding with six fluorine atoms, exceeds the octet rule by utilizing its empty d-orbitals, accommodating a total of 12 electrons around the sulfur atom. Another example, Phosphorus can have an expanded octet by bonding with five chlorine atoms, utilizing its empty d-orbitals to accomm...

Isabelle Huerta 2I

The coordination number refers to the total number of ligands or donor atoms attached directly to the central atom within a coordination complex. It does not consider the nature of the bonds (single, double, etc.) formed between the ligands and the central atom, but rather the count of ligands surro...

Isabelle Huerta 2I

A Lewis acid is a species that can accept an electron pair. It's defined as an electron pair acceptor. It is based on electron pair donation and acceptance. A Lewis base is a species that can donate an electron pair. It's defined as an electron pair donor. A Brønsted-Lowry acid is a species that don...

Isabelle Huerta 2I

Count Electron Groups: Each bond (single, double, or triple) and each lone pair around the atom counts as one electron group. Determine Hybridization: Two Electron Groups: Hybridization: sp Three Electron Groups: Hybridization: sp2 Four Electron Groups: Hybridization: sp3 Five Electron Groups: Hybri...

Isabelle Huerta 2I

The strength of a conjugate base or acid is linked to the strength of its parent acid or base, determining its ability to accept or donate protons and the rate of proton transfer reactions. Stronger acids tend to have weaker conjugate bases, while stronger bases tend to have weaker conjugate acids.

Isabelle Huerta 2I

The resulting Lewis structure of urea (CO(NH2)2) should show carbon double-bonded to oxygen and single-bonded to two nitrogen atoms, each nitrogen bonded to two hydrogen atoms.

Isabelle Huerta 2I

Lewis acids and bases are generally defined as electron pair acceptors and donors, respectively. However, some situations involve single electron transfers, especially in radical reactions or in certain chemical environments where species might accept or donate single electrons to form bonds or stab...

Isabelle Huerta 2I

While hydrogen bonds are strong for intermolecular forces, they are weaker than covalent bonds. Covalent bonds involve the sharing of electrons between atoms, which generally requires more energy to break compared to the electrostatic interactions involved in hydrogen bonding. So, in terms of interm...

Isabelle Huerta 2I

There's no direct relationship between formal charge and oxidation number. They can be different for the same atom in a molecule or ion. Formal charges help determine the best Lewis structure, indicating electron distribution, while oxidation numbers are used to track electron transfer in chemical r...

Isabelle Huerta 2I

hydrogen bonds between molecules significantly raise boiling points by creating stronger intermolecular attractions compared to substances without hydrogen bonding. When comparing substances, molecules that can form hydrogen bonds tend to have higher boiling points than those lacking this capability...

Isabelle Huerta 2I

Ionization energy is the energy needed to remove an electron from an atom, making the atom positively charged. The trend on the table for the first ionization energy is increase from left to right and it decreases down the group. Second ionization energy is the energy required to remove a second ele...

Isabelle Huerta 2I

ionic bonds are representing through Lewis dot structures to indicate the transfer of electrons between atoms in forming ions. Ionic bonds show complete transfer from one atom to another. Covalent bonds are represented by the Lewis structure to show electron pairs shared between atoms. Diagrams of c...

Isabelle Huerta 2I

While we can’t use the De Broglie wavelength calculation, photons are characterized by the wavelength, frequency, and energy.

Isabelle Huerta 2I

Some of the most commonly used ligands are: (1) H2O (water) (2) NH3 (ammonia) (3) Cl- (chloride ion) (4) CN- (cyanide ion) Water is very abundant and are able to coordinate with various metal ions. Ammonia and Chloride ions are able to donate a lone pair of electrons. Cyanide ions have strong coordi...

Isabelle Huerta 2I

The measurable wavelike property in electrons is the electron’s ability to exhibit wave-like behavior. The electron shows characteristics of waves like interference. The momentum of the electron is inversely proportional to their wavelength.

Isabelle Huerta 2I

hi,

i came across a little problem while studying...how do we know which equation to use when we need to go from one to the other. for example, if we are given pOH and we need to find [H], how do we know which equations would best fit the situation?

thanks.

Isabelle Huerta 2I

hi,

can somebody please explain to me the key properties that enable the bases to neutralize acids. what is the difference in ability when the base is organic vs inorganic.

thanks.

Isabelle Huerta 2I

hi,

does anyone know of a good example where the structure of the acid played a key role in the strength of the acid.

thanks.

Isabelle Huerta 2I

hi,

what would you say are the most prominent differences in the structure of inorganic acids and organic acids? i'm hoping this will help me better distinguish the two come the final exam.

thanks.

Isabelle Huerta 2I

hi,

i wanted some clarification on inorganic acids. how does the strength of inorganic acids affect its dissociation process and it's affect on the behavior in aqueous solutions?

thanks.

Isabelle Huerta 2I

hi,

another topic i was confused about was how hybridization affects the molecular geometry of the central atom and its bond angles?

thanks.

Isabelle Huerta 2I

hi,

I'm having trouble remembering how many types of hybridization there are and what they are?

thanks.

Isabelle Huerta 2I

hi,

what are some characteristics that we can rely on when identifying the phases of liquid crystals?

thanks.

Isabelle Huerta 2I

hi,

apologies but i struggle the most in this topic. I wanted clarification on how hydrogen bonding has an affect on the boiling and melting points of compound elements?

thanks.

Isabelle Huerta 2I

hi,

I was curious about the impact that london forces has on the boiling points of any elements that aren't noble gases.

thanks.

Isabelle Huerta 2I

Hi,

What contribution do induced dipole-induced dipole interactions have on non-polar molecules?

Thank you!

Isabelle Huerta 2I

hello,

I was going through the problems and I wanted some clarification on this. How can bond length influence the amount of energy it can store?

thanks.

Isabelle Huerta 2I

Hi,

I was wondering, what factors can be used when considering the magnitude and direction of a dipole moment?

Thanks.

Isabelle Huerta 2I

Hi,

I was wondering, what factors can be used when considering the magnitude and direction of a dipole moment?

Thanks.

Isabelle Huerta 2I

Hi,

I was wondering, what factors can be used when considering the magnitude and direction of a dipole moment?

Thanks.

Isabelle Huerta 2I

Hi,

I was playing around with the structure of O3, since it can take on different types of bonds in different elements. How would these resonance structures help me in determining which structure is the most stable, if there is one.

Thanks!

Isabelle Huerta 2I

Hi,

I wanted to know if there was a way to better understand the electronegativity difference between atoms that contribute to polar bond formations?

Thanks.

Isabelle Huerta 2I

Hi

I was just doing some practice problems and came across a thought. If Carbon were to bind to Oxygen, since Oxygen can carry a double bond w/ 2 lone pairs and Carbon can carry up to four bonds, would Oxygen be able to have 2 double bonds with Carbon and it be considered a full octet?

Thanks.

Isabelle Huerta 2I

Can somebody refresh my memory on what role protons play in determining atomic radius? Thanks.

Isabelle Huerta 2I

Can someone walk me through how to find the spectral lines when given a shell number?

I was looking through the past homework assignments and got stuck figuring this out, thanks.

Isabelle Huerta 2I

Hi, so when calculating the theoretical yield. Do we need to find the masses of all chemical equations involved? How do we pinpoint which formulas need to be calculated and which elements are left untouched/not calculated?

Isabelle Huerta 2I

Hi, I just wanted some quick clarification. When counting sig figs, all leading zeros, even if after a decimal point, don't count? But any zeroes that are after a real number, and after a decimal point, will still count as significant figures?

Isabelle Huerta 2I

Hi, you can find Pf. Lavelle's recording on the BruinLearn website. It should be under the tab labeled "UCLA Media Reserves."

Isabelle Huerta 2I

A program that I find really helpful is AAP (Academic Advancement Program). They have PLF sessions which are led by undergraduate students. They are free and very helpful tutoring sessions that happen twice a week. I highly recommend looking into this program if you haven't already.

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