CHEMISTRY COMMUNITY

Seungyeon_Chi_1K

Each order has different units each reaction order corresponds to different mathematical relationship between concentration of the reactants and the reaction rate. The reaction rate depends on the concentration per unit time which allows it to change for every order of reactions, thus leading the k ...

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K value is always positive as the negative sign represents only the fact that the concentration of the reactants are being used up in the reaction.

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What are some things that we should understand before the test, specifically what would increase or decrease k in second order reactions?

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Hello,

Can someone give a step by step explanation on how to solve for the rate law when there are three equations that are slow, fast, and and fast in both sides?

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How do you determine the first and second order reactions and what factors would we need to look at to determine?

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What exactly is the 'unique' rate that was mentioned during lecture? And what's the significance of it?

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If cell potential is positive, then ΔG will be negative. If it's negative, then ΔG will be positive.

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The oxidation state would have to be +1. The oxidation state for O is -2 and for total oxidation state, it would be -1. Therefore, the Br would need to have a +1 charge.

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Hello,

Can someone explain the difference between these two types of cells and how the difference contributes to how you solve problems that involve them?

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Hello,

Can someone explain what the difference of using log and ln has towards the Nernst equation? Why would we have to use two different functions for solving?

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To determine if a redox reaction occurs in an acid or base, you would have to look into the chemical equation for any H+ or OH- ions. However, the problems will most likely tell you whether the reaction is acidic or basic.

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The strength of an oxidizing agent is determined by the value of its standard electrode potential, with higher values showing stronger oxidizing abilities.

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The problem will state whether the system is adiabatic or not. If the U and w are equal to each other, then you can derive that the system is adiabatic and q=0.

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Reversible reactions allow minimal entropy changes as the system is in equilibrium with its surroundings. However, irreversible reactions have entropy change because there is no constant temperature and there is always disorder within the system.

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When would it be the most ideal to use the Van’t Hoff equation?

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Hello,

Does change in enthalpy have a relationship in change in internal energy? If so, how are they related and affect each other?

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Temperature increasing would lead to an increase of entropy whereas temperature decreasing would lead to a decrease in entropy as well.

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When the change in volume is zero, it means the system is not doing any work on its surroundings or having work done it by the surroundings. In that case, delta U would be equal to the heat added to the system.

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What does it really mean if the system is spontaneous? How do you determine if it is spontaneous as written or in reverse?

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Hello,

Can anyone explain what residual entropy essentially means and how we can identify which compounds would have residual entropy by their molecular structures?

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How do you know just by looking at the chemical equations, whether the system is open, closed, or isolated? Is there a determining factor we can look for easily?

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What is the essential use of integral when calculating work of expansion? Why is there a need for integrals?

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Specific heat capacity measures how much heat energy is needed to raise the temperature of a certain amount given of a substance by 1 degree of either Celsius or Kelvin, whereas normal heat capacity measures the same thing but of one mole of a substance by 1 degree. They are essentially the same thi...

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Calorimeters should be used whenever there is a need to accurately measure heat changes within a system that is going through a physical or chemical process. They are helpful in terms of measuring reactions that involve the release or absorption of heat.

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Hello,
How do you know how to determine if the answer is 4x bond/-4x bond or enthalpy of formation/combustion?

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Can someone explain how to determine if the reactions are endothermic and exothermic just by looking at the strong and weak bonds?

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The phase change takes a longer time because there is a need for stronger intermolecular forces to be broken during vaporization.

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During phase changes, the temperature remains constant because the substance is only changing its state, not necessarily increasing its temperature. The energy is being absorbed or released during these transitions which doesn't affect the substance's temperature.

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Autoprotolysis refers to the process of the self-ionization (essentially a substance donating a proton to itself). Autoprotolysis occurs in water in which water ionizes itself with temperature influencing the level of ionization.

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Conceptually speaking, the pKa provides the tendency of a weak acid to donate a proton while the pH predicts the degree of ionization of the acid in a solution.

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How do you know which direction of reaction (forward or reverse) is favored? What do you need to look at in terms of determining direction?

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How do you know which direction of reaction (forward or reverse) is favored? What do you need to look at in terms of determining direction?

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Hello,

In lecture, Dr Lavelle wrote that unlike a strong acid or base which is completely ionized in solution, weak acids and bases are not. Why is this the case?

Thank you

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Can somebody explain in detail how and why the equilibrium would change in response to temperature?

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Hello,

What does it really mean when the reaction is shifting right/left? How does this direction change how we look at reactions and how does Le Chatelier's Principle relate to this?

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Kw is essentially represents the equilibrium constant for the ionization of water. It's Kw not Kc because we are talking about the ionization of water not exactly equilibrium constants for reactions involving reactants and products in the same phase (Kc).

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pH directly measures the acidity of a solution, while pKa provides information solely about the strength of an acid. Lower pH values signify higher acidity, while lower pKa values essentially indicate stronger acids.

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A pH greater than the pKa indicates a more basic environment. When pH > pKa, there's a higher concentration of deprotonated, charged species (conjugate base) compared to the protonated form (acid). This suggests that more charged, deprotonated species present in the solution.

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There are no units for K because it is considered as a constant that serves to show the proportion of products as to reactants that are present when the reaction is at equilibrium.

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A heterogenous equilibrium is when there is one or more reaction or products in different phase. On the other hand, a homogenous equilibrium is when all reactants and products are in the same phase.

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Hello,

How does molarity exactly contribute to making a difference in the ICE table? Why do we include molarity instead of solely the amount of moles?

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Hello,

Can someone explain how the Q and K relate to each other and how they affect one another as well within a chemically balanced equation?

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Hello! How are you supposed to name the mono-, bi-, tri-, or poly- dentates and also what are chelating ligands and how are these two concepts related to each other?
Thank you!

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Hello!

I am confused as to what exactly conjugate acids and bases are and how to distinguish them apart from the bronsted acids and bases and how to find them within the reaction equation.

Thank you!

Seungyeon_Chi_1K

Hi! I'd say it's pretty hard to know the strength of an individual acid/base because it can depend on the specific context and reaction conditions. You have to take note that: Arrhenius: Acids - substances that produce H+ ions in aqueous solution Bases - substances that produce OH- ions in aqueous s...

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The ability of an anionic ligand to bind to a transition metal is primarily due to its lone pair of electrons. Anionic ligands derive their negative charge from the presence of these lone pairs. These lone pairs and their ability to form coordinate bonds enable anionic ligands to bind to transition ...

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Hello, are there any exceptions we have to note in terms of hybridization?

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What exactly are you supposed to look for in order to name coordination compounds?

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The negative pole in a molecule is determined by both factors. If there's a significant EN difference in a bond, the more electronegative atom becomes partially negative. Also, lone pairs lead to localized negative regions in a molecule.

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A seesaw molecule has four bonds and one lone pair around the central atom, resulting in five regions of electron density. The central atom forms four bonds with surrounding atoms and one lone pair.

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Hello,

Are we just expected to remember the bond angles or is there an easier way to understand them?

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Can someone please make an easy guideline of steps as to how to give the right hybridizations represented in the Lewis structures?

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CH2Cl2 is a tetrahedral molecular shape with four bonds, but the polarity of C-H bonds differs from that of C-Cl bonds. The molecule would be nonpolar if C-H and C-Cl bonds were directly across from each other, canceling out dipole moments. However, in a tetrahedral molecule, this arrangement cannot...

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Yes, adjusting the placement of lone pairs in various valid Lewis structures can alter the molecular shape. This is because the repulsion between the lone pairs influences the 3 dimensional arrangement of atoms, ultimately determining the molecule's shape.

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How do you determine the most stable structure out of the multiple resonance structures? Is it by their overall charges?

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Hello,
I've taken notes from Dr. Lavelle that P, S, and Cl are exceptions as to having expanded valence shells. Why is that so?

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No, polarizability only applies to the ability of the anions' electron clouds to get distorted. Cations would have polarizing power instead which measures their ability to distort the anions' electron cloud and further create covalent character. So cations: polarizing power, anions: polarizability. ...

Seungyeon_Chi_1K

Usually, I would look over the kind of intermolecular forces the bonds have and what type of bond as well. For example, if you had to look over HCl and NaCl, NaCl would have a higher melting point because it is an ionic bond which is harder to break.

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What is the difference between cations and anions and what key feature sets them apart?

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Hello, can someone explain all the variables in the formal charge equation and how the equation is formulated?

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Bond character refers to the covalent and ionic nature of a chemical bond. Bonds with higher covalence tend to have shorter bond lengths because of their more evenly shared electrons, whereas bonds with higher ionic feature have longer bond lengths as electrons are transferred which ultimately leads...

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Hello, electronegativity is known to increase with higher nuclear charge and smaller atomic radius because these factors influence the ability of an atom to attract electrons in a chemical bond.

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What is the key difference between sigma and pi bonds in the context of chemical bonding? What part of their properties influence the structure of molecules?

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Hello,

Can someone explain what exactly makes Resonance Structures different from Lewis Structures? Any key components? Thank you

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Hydrogen bonds form between a hydrogen atom and an electronegative atom with a lone pair.

They are stronger than ionic bonds because of their covalence and the existence of their partial charges that allows for a lot of hydrogen bonds to form between molecules.

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Ionic bonds do involve the interaction of positive and negative charges, but they don't have dipole moments like in polar covalent bonds because there is no electron sharing within the ions themselves. Instead, ionic compounds are put together by the electrostatic attraction between the charged ions...

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Can someone please explain what exactly the black body is and how the equation was made?

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Hello, does it matter how you order your electron configurations? Would it be wrong if it was 4s^2 3d^10 when it could be 3d^10 4s^2?

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You should find the diameter rather than using the radius. That will make your answer more accurate in terms of the uncertainty in position used by the Heisenberg's Uncertainty Principle.

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The "particle in a box" is a model that shows how a particle's energy is measured when confined within a box. Heisenberg's Uncertainty Principle shows that there is a fundamental limit to how precisely we can know both the position and momentum of a particle.

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In the lecture, Dr. Lavelle went through all the variables in the equation but didn't really go over how the variables come together to make up the equation. Can someone explain how the equation can be used for certain problems and how to solve?

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Hello, does anyone know how to solve question 18 from the second homework assignment?

Seungyeon_Chi_1K

Hello, just a general question:
Can someone explain why only the s- orbital has a symmetric e- density distribution as opposed to p-,d-,f- orbitals that have non-symmetric distributions?

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In quantum mechanics, angular quantities are usually answered in radians rather than degrees. So I'd say when calculating with the Heisenburg's Indeterminancy Equation, we should use radians to be safe.

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Professor Lavelle is going to thoroughly go over what's going to be on the midterm this Friday, but here's what I heard: it's all going to be multiple choice with mixed conceptual and mathematical with some true or false questions as well! Hope this helps :)

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How do you determine a limiting reactant when given a problem?

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I thought we were supposed to answer with the most amount of sig figs given in the question, but in a pdf that I saw in bruinlearn, it tells us to answer with the least amount of sig figs given. Which way am I supposed to answer when answering questions for this class?

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What is the significance of the negative sign in the Shrodinger equation?

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How does the photoelectric effect demonstrate the particle-like nature of light and understanding on the behavior of electrons in chemical reactions?

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Since there is an excess of propyl magnesium bromide, that means that propyl magnesium bromide is not the limiting reactant. The limiting reactant would be the 2-butanone.

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You might want to make sure you have calculated the molar mass of CuNO3 correctly and get the number of moles. After, try the V = n/m equation and convert the answer to mLs by multiplying by 1000.

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You might want to make sure you have calculated the molar mass of CuNO3 correctly and get the number of moles. After, try the V = n/m equation and convert the answer to mLs by multiplying by 1000.

Seungyeon_Chi_1K

I'd say it is generally safe to keep as many decimal places as possible throughout your calculations to minimize rounding errors.

Seungyeon_Chi_1K

Your answer should have 4 sig figs. When answering questions with sig figs, your answer should always correspond with the number of the largest sig figs.

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