CHEMISTRY COMMUNITY

Eileen Si 1G

In what scenario would you use a differentiated rate law versus an integrated rate law? Also, will we have to know how to derive or integrate such rate laws?

Eileen Si 1G

How can you identify which step of the reaction mechanism is the slowest step? Or will this just be given in the problem itself?

Eileen Si 1G

Naneeta Desar 1K wrote:As temperature increases, so does the rate constant.

Does this apply to both reactions with high activation barriers and low activation barriers?

Eileen Si 1G

How do you differentiate and identify whether a reaction is pseduo first order/second order or just simply first order/second order? Also, what does it generally mean when a reaction is pseduo first/second order?

Eileen Si 1G

How does changing temperature (i.e. raising or lowering) affect the rate constant of reactions with high activation barriers versus the rate constant of reactions with low activation barriers?

Eileen Si 1G

What topics will be tested on the final? Will it be cumulative or only focus on certain focuses?

Eileen Si 1G

In order to solve for this mathematically, you probably need to memorize or at least understand the basic concepts from the reading, so I would put emphasis on the memorizing in the form of reading aspect of the material.

Eileen Si 1G

Cl2(g) is acting as both an oxidizing and reducing agent, so it will also be involved in the oxidation reaction. Because oxidation is a loss of electrons, Cl2(g) will react with H2O(l) to produce HClO(aq), Cl2(g), H+(aq), and electrons.

Eileen Si 1G

Are you referring to Outlines 4 and 5 from Lavelle's website? If so, the second page from the thermo outline (4) and everything on outline 5 including any thermo is fair game for Exam 2. I'm referring to the Focuses from the textbook within just Outline 4 specifically. So like, whether or not topic...

Eileen Si 1G

Problems 5G: 13, 15, 17, 19, 21; 5J: 11, 13, 15, and 5.55, 5.61 are the problems that should correspond with the second page as stated from Lavelle's syllabus and Thermodynamics outline.

Eileen Si 1G

Will the only part of thermodynamics that will be tested on Test 2 be from Focus 5 or will other parts of Focus 4 be on the test as well?

Eileen Si 1G

You would write the half-reaction without Pt(s), since it simply serves as a solid electrode for the cell diagram. Because a reduction reaction is occurring in the anode, there is a gain of electrons added to O2(g) as it also reacts with water, H2O(l) to produce hydroxide, OH-(aq). So the anode hal...

Eileen Si 1G

How do you find the order of the reactant B, when given that its concentration is 1.25 mmol.L-1 and its initial rate is 17.4 mmol.L-1.s-1 in Experiment 2, and its concentration is 3.02 mmol.L-1 and its initial rate is 50.8 mmol.L-1.s-1 in Experiment 3. I understand how to find the order for reactant...

Eileen Si 1G

You would write the half-reaction without Pt(s), since it simply serves as a solid electrode for the cell diagram. Because an oxidation reaction is occurring in the anode, there is a loss of electrons from water as it oxidizes to O2(g), H+(a), and electrons. So the anode half-reaction is: 2H2O(l) --...

Eileen Si 1G

For part c) of problem 6L.7, it asks to find the galvanic call for Cd(s) + 2 Ni(OH)3(s) --> Cd(OH)2(s) + 2 Ni(OH)2(s).
In the solutions manual, it uses KOH(aq) in the cell diagram instead of OH-(aq). Why is this?

Eileen Si 1G

Au in its solid form is more stable than Au+ in its aqueous form, so it is used in the reduction half-reaction as well as the oxidation half-reaction.

Eileen Si 1G

For this specific reaction, Au + acts in both the cathode and anode reaction, so you should see both in each reaction. For cathode, the half reaction is: Au+ + e- -> Au For anode, the half reaction is" Au3+ + 3e- -> Au+ Then, you should multiply the half reaction of cathode by 3 and flip the a...

Eileen Si 1G

The oxidizing agent is what is being reduced in the reaction, so it gains electrons, while the reducing agent is being oxidized so it loses electrons. One way to identify which is which is by looking at the initial and final oxidation numbers of an element. If the oxidation number is greater in the ...

Eileen Si 1G

The purpose of the salt bridge is to maintain the balance of the charges as the electrons move from one half cell to the other.

Eileen Si 1G

For basic solutions, you still need to balance the reaction with H+, like in an acidic solution, but add OH- for every H+ that you have in order to cancel the H+ out with the OH-. Hopefully this makes sense.

Eileen Si 1G

How do galvanic and voltaic cells relate to spontaneity of a reaction?

Eileen Si 1G

Is X2(g) = 2X(g) where X is a halogen an endothermic or exothermic reaction, and why? Wouldn't it be an exothermic reaction because the bond between an X2 molecule is broken to become 2 separate X atoms?

Eileen Si 1G

For homework problem 5G.21, it asks to calculate the equilibrium constant at 25 C for the following reaction, by using data in Appendix 2A: 2H2(g) + O2(g) = 2H2O(g). I know that you have to use the equation, delta G=-RTlnK in order to solve for equilibrium constant, K, but would delta G be the delta...

Eileen Si 1G

You can use the ideal gas law, PV = nRT to calculate the amount of moles, since every other value for the equation is given.

Eileen Si 1G

What is the delta entropy of the surroundings and system during an irreversible expansion, and is it any different to an adiabatic system where q = 0?

Eileen Si 1G

Do delta G, delta H, and delta S have nonzero values at equilibrium, or are they equal to 0 since there is no net change occurring due to the system being at equilibrium?

Eileen Si 1G

Adding on, for part c, ethene is a gas, while polyethylene is a solid, so naturally, ethene will have higher entropy than polyethylene.

Eileen Si 1G

Why does Gibbs free energy depend on the equilibrium constant and pressure? Also, is Gibbs free energy a state function?

Eileen Si 1G

According to Lavelle's website, the topics covered on the midterm will be Chemical Equilibrium, Acids and Bases, Thermochemistry, and Thermodynamics, so yes, you should know all of Thermodynamics.

Eileen Si 1G

I believe that they will include the temperature in the given problem, however, I would still double-check with your TA to make sure.

Eileen Si 1G

After calculating the enthalpy for the TNT, which should be in the units of kJ.mol-1, you need to convert this value into kJ.g-1 by using the molar mass for TNT. Then, this is when you bring in the density value. First, you need to convert it into g.L-1 and multiply it by the enthalpy that you found...

Eileen Si 1G

Adding onto what the person before me said, the steeper the heating curve, the lower the heat capacity, and vice versa - the shallower the heating curve, the higher the heat capacity.

Eileen Si 1G

Heat capacity is the ratio of the heat supplied to the rise in temperature produced. Specifically for ideal gases, it requires more heat to achieve the same rise in temperature for constant pressure than it does at constant volume. While at constant volume, all the heat supplied goes into raising th...

Eileen Si 1G

Yes, you're on the right track, but for q of ice, you also need to account for the fact that the ice melting into water also gives off energy that needs to be added to the calculation for q=mCdeltaT, so it would be the grams of ice converted into moles and multiplied by the standard enthalpy of phys...

Eileen Si 1G

When would you know to use w=-P*delta V versus w=-nRTln(V2/V1) to calculate work of expansion? (Like in homework 4A.5)

Eileen Si 1G

A closed system can exchange energy with its surroundings, but not matter, while an isolated system cannot exchange either energy nor matter. For example, an example of a closed system is a pan with a lid, on top of a stove. The pan is exchanging heat energy from the fire, but not the amount of matt...

Eileen Si 1G

q is the amount of heat that is transferred into or out of a system and is measured in J (joules). delta H is the change in enthalpy of a system and is measured in kJ (or J) * mol-1.

Eileen Si 1G

For part a, I believe it's 343K for the final temperature and 935.1J for the change in enthalpy, and part b it's 374K for the final temperature and 947.6J for the change in enthalpy.

Eileen Si 1G

You can pick them at 3034 Young Hall, but I'm not sure when we are allowed to pick them up or if we can go at anytime this week.

Eileen Si 1G

To clarify, solids and liquids would not be included in a K expression, right? So, only liquids and aqueous molecules would be involved?

Eileen Si 1G

Khan Academy and Bozeman Science

Eileen Si 1G

To find the mass of Na2O in the first flask, you take the molar concentration of NaOH that you calculated in part aii) and divide by 0.2 L (200 mL) as given in the problem to cancel out the volume and just get moles of NaOH. Then, you need to use stoichiometry to convert moles of NaOH to moles of Na...

Eileen Si 1G

Is it possible to calculate K for an unbalanced equation? Or can you only calculate Q?

Eileen Si 1G

Catalysts increase the rate of the reaction, but emerge unchanged from the reaction, so they do not affect the amount of product formed.

Eileen Si 1G

Yes, you are on the right track. For HClO, the Ka = 3.0 x 10^-8, and the variable in the Ka expression would be the amount of molar concentration of HClO, which you can find since you are given the pH. So, it would be Ka = 3.0 x 10^-8 = [HClO]^2/x-[HClO], and you would just solve for x.

Eileen Si 1G

Does anyone know when we can pick up the finals from chem 14A? I know that it is this week, but am unsure if we can pick them up at any time, or if there a certain time-frame in which we can pick them up?

Eileen Si 1G

Adding onto what the previous person said, because the autoionization of water is an endothermic reaction, the change in enthalpy is positive, because endothermic reactions require heat, which causes the products to be more favored than the reactants.

Eileen Si 1G

To add on, the reaction favors the products on the right side, and we learned today in lecture that a reaction that favors the formation of products is endothermic because they require heat. On the other hand, exothermic reactions give off heat when forming products, so hearing will favor the format...

Eileen Si 1G

In the textbook, the question asks to use information from Table 5E.2, but I can't seem to find it anywhere. By any chance, is this just a typo where they meant to refer to Table 5G.2 instead? If not, on which page can I find Table 5E.2?

Eileen Si 1G

Can we pick them up at any time, or is there a certain time-frame in which we can pick them up?

Eileen Si 1G

How does increasing or decreasing the partial pressure of a reactant affect the partial pressure of the product, and vice versa for a change in product and its effect on the reactant?

Eileen Si 1G

Question 5J.5b in the homework gives the following reaction: H20(aq) + C(s) = H2(g) + CO(g). Will the reactants or products be favored by an increase in total pressure due to compression, and why?

Eileen Si 1G

This may be an obvious question, but what is the difference between Q (reaction quotient) and K (equilibrium constant)?

Eileen Si 1G

In the equation, CO(g) + H2O(g) = CO2(g) + H2(g), if the concentration of CO is increased, would the concentration of H2 also increase? Or would it remain the same and not change?

Eileen Si 1G

Exothermic equations have a negative value because heat energy is being released into the environment, and the enthalpy of the products is lower than the reactants.

Eileen Si 1G

By looking at the balanced chemical equation. If the molecule does not have a stoichiometric coefficient, then the change is simply x. If the molecule does has a stoichiometric coefficient, then the change is the coefficient * x. Also, if the molecule is a reactant, then the change is negative, but ...

Eileen Si 1G

Also, would you be able to divide the concentrations (in moles) by 10.0 L in the beginning so the concentrations in the equilibrium table are in mol.L^-1 instead of mol and calculate the concentrations of the different products and reactants from there instead of dividing the moles by 10.0 L at the ...

Eileen Si 1G

For number 5I.23 in the homework, why is the initial concentration (in moles) for CH4(g) 0 instead of 0.478?

Eileen Si 1G

When listing the bond order for pi bonds, will it always be 2p hybridized? For example, if the sigma bond was sigma(C2sp^2, C2sp^2), would the pi bond then be pi(C2p, C2p) hybridized?

Eileen Si 1G

Thank you! Does anyone know of any other traits about acid/base strengths/weaknesses that you should be on the lookout for?

Eileen Si 1G

You can calculate this by looking at the electronegativity values for each of the elements and subtracting the difference between them. If the electronegativity difference is greater than 2, then the bond is ionic, so for this problem, the closer the differences are to 2, the more ionic they are.

Eileen Si 1G

Hi! I don't know if you stayed until close to 6pm, but he ended up coming in late and is still going over the review material.

Eileen Si 1G

How do you distinguish the difference between a strong versus weak acid or a strong versus weak base? Does it have to do with plain memorization, or are there any tricks or ways to tell the difference between them?

Eileen Si 1G

In his Final Exam Review Sessions sheet, it states that he's going to have his own review where he'll go over his past test questions, but it'll be during regular lecture times, so he won't host any of his own extra review sessions outside of scheduled lectures.

Eileen Si 1G

The UA's are also going to be holding another Final Review Session this Friday night. They posted a practice final under the name "Marshmallow" that should mimic the sort of problems that will be on the final.

Eileen Si 1G

What about for bases?

Eileen Si 1G

I'm not 100% sure, but you could also probably check the Test Bank at the SAC to see if they have any old finals.

Eileen Si 1G

What is the relation between electronegativity and strong/or weak acids? Also, can electronegativity be used to determine whether a base is strong or weak, or is it just relevant for acids?

Eileen Si 1G

How do you determine whether a ligand is polydentate or not?

Eileen Si 1G

Also, what are the effects of chelation, if there are any?

Eileen Si 1G

How do you know which ligands are capable of forming chelates, and what is the significance of chelation in relation to coordination compounds?

Eileen Si 1G

After drawing a Lewis structure for both of these molecules, you can see that the arrangement of the atoms in butanol allow for a Hydrogen bond between H and N, which is a stronger interaction force than just the dipole-dipole interaction forces and London dispersion forces in diethyl ether. As a re...

Eileen Si 1G

H2SeO4 is also polar, so it will have dipole-dipole interactions as well as London dispersion forces.

Eileen Si 1G

How is the polarizing power of cations and melting point related? In other words, does having a higher polarizing power indicate a higher or lower melting point?

Eileen Si 1G

How can you identify the difference between a dipole moment versus an induced dipole moment? Is it possible to tell by looking at the Lewis structures, or do you have to use another method to figure if it's dipole or induced-dipole?

Eileen Si 1G

Does anyone know if it will matter whether or not we say "bent" or "angular" to describe certain VSEPR models on the test?

Eileen Si 1G

So will test 2 include Focus 2D from Outline 3 (Chemical Bonds), or will it include everything afterwards?

Eileen Si 1G

For part b of 2E.7, why is it that there is only one bond angle between S, O, and Cl? I understand that there is one lone electron, but where would this extra single electron go in a Lewis structure model for SOCl if a Lewis structure for this molecule is even possible?

Eileen Si 1G

Test 2 should cover topics ranging from Lewis structures, intermolecular forces, and the VSEPR Model. Hopefully I'm not missing anything!

Eileen Si 1G

Will any of the topics that we were tested on the midterm also be included in Test 2?

Eileen Si 1G

How can you determine whether a lone pair is in a hybridized orbital? Like for NH3, N is sp3, but why is the lone pair on N not in an unhybridized p orbital instead?

Eileen Si 1G

Adding on to what the person above me said, I think he will provide us with the chart also because we haven't been taught yet to calculate the electronegativity values for each element and most of these values have already been found in outside professional labs.

Eileen Si 1G

Hybridization describes the process where atomic orbitals fuse together in order to form new hybrid orbitals. To determine hybridization, you have to look at the number of atoms attached to the central atom and add it to the number of lone pairs. If the answer is 4, then the atom is sp3, if the answ...

Eileen Si 1G

How does electronegativity relate to finding dipole moments?

Eileen Si 1G

Why are dissociation energies always positive? Is energy released or gained when a bond is broken?

Eileen Si 1G

Triple bonds are the shortest and strongest, and single bonds are the longest and weakest, with double bonds being somewhere in the middle of single and triple bonds. This is because single bonds are more easily broken and likely to be involved in a reaction, while stronger bonds are harder to break...

Eileen Si 1G

How do dipole moments determine polarity, like whether a covalent bond is polar or nonpolar?

Eileen Si 1G

How can you tell whether one element is more polarizable than another? Also, is there a difference between an element that has more polarizing power vs. an element that is the most polarizable?

Eileen Si 1G

What is the difference between ionization energy and electronegativity? If so, is there a way to differentiate between the two just by looking at the periodic table?

Eileen Si 1G

Why does Oxygen have a lower ionization energy than Nitrogen? Are there are other elements that are special in the respect that they have lower ionization energies than the element to their right?

Eileen Si 1G

The midterm should cover the topics of Fundamentals, Quantum World, and some of Chemical Bonds.

Eileen Si 1G

I think that we need a blue book, since it is an official midterm, as well as a scientific calculator for basic calculations. Other than that, some extra pens would be good to have on hand too. And I haven't heard anything about the midterm locations yet, so he will probably be sending out an email ...

Eileen Si 1G

The Midterm should cover topics from Fundamentals, the Quantum World, and some of Chemical Bonds as well.

Eileen Si 1G · Re: posting on chemistry community The deadline is by 11:59pm Sunday night

The deadline is by 11:59pm Sunday night

Eileen Si 1G

Does anyone know if the Fundamentals topic that we covered for the first test will be included on the midterm? Or will the midterm just be testing us on the Quantum World and Chemical Bonds?

Eileen Si 1G

For part d of this question, it asks what the ground-state electron configuration is for Ag+. I thought it was [Kr]4d^8 5s^2, but the solutions manual says that it is [Kr]4d^10. Is this because the two electrons from the 5s shell go to the 4d shell? And if so, why does this happen?

Eileen Si 1G

What is the difference between sigma and pi bonds? Are there ever cases where both of them will be present at the same time in the same molecule?

Eileen Si 1G

Sigma and pi bonds are significant because they can be utilized to predict how molecules behave by providing you with the shape of the molecule.

Eileen Si 1G

For an anion, you would add the negative charge to the number of electrons in order to figure out the total number of electrons to draw in the Lewis structure. Moreover, you can then draw brackets around the whole Lewis structure and write the negative charge outside the top right corner of the brac...

Eileen Si 1G

When an electron is delocalized, it is able to be rearranged into different molecular structures, because it isn't bound to just one atom or ion. As a result, there is resonance and you can have multiple structure with bonds in different locations.

Search found 120 matches