CHEMISTRY COMMUNITY

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You must set -RTlnK equal to ∆H-T∆S. Then you just need to divide the -RT to the other side such that you only have link on one side

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Because we know that K=Ae^(-Ea/RT), we could derive it in such way that we can find the slope of the activation energy linearly.

We can receive the equation attached to this post. We plug in our rate constants and the initial and final temperatures such that we can receive our Ea

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Lavelle mentioned how the steady-state approach Is arduous and how the pre-equilibrium approach accomplishes the same thing. So you should be fine just knowing the latter method.

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What distinguishes the difference between kinetic stability and thermodynamic stability? If you could relate it to activation energy and ∆G value (negative or positive), I would appreciate it.

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Why isn't the rate for this (k2•k1/k1')([ClO-][H2O][I-]/[OH-]). The answer key didn't include [H2O]. Is it because it is a catalyst? If so, does that idea apply to all rate laws?

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This is just stoichiometry. I think of it as this: since the concentration of B rises to 0.034M, I convert that into A using stoichiometry. 0.034(2mol A)=0.068M of A. What this means was that for the concentration of B to increase, 0.068M of A had to be used. Hence, 0.068M of A was lost from the ini...

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This question is unique because this is an acid-base reaction. Hence we know that for this question, the weak acid will donate an electron: HF<--->H+(aq) + F-(aq) This means that the Ka= [H+][F-]/[HF]. Because the half reactions must adhere to this acid base reaction, the Ecell value is negative, -0...

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How do we write a rate equation when there is a rate determining step along with several fast elementary steps?

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Why is it that we need to know derivatives and slopes at particular points in kinetics? Are those values calculated or more theoretical?

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If that is the case, I believe you would have to include a salt into the cell diagram onto the oxidation side (i.e. KOH) in order for ions to transfer and neutralize the charges. There was a homework problem like that, Chapter 14.15 in the 6th Edition. Cd(s) + 2Ni(OH)3(s) --->Cd(OH)2(s) + 2Ni(OH)2(s...

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What range in volts does a voltmeter need to have to measure pH in the range of 1 to 14 at 25 Celsius if the voltage is zero when pH is 7? I understand everything for the most part, but can anyone explain to me why we have to do this: .025693ln(0.1/1x10^-13)= 0.710V .025693ln(1x10^-14/1.0)=-0.828V W...

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For part a, the equation is given as AgBr(s)<---->Ag+(aq)+Br-(aq).
How do we figure out what the half reactions are? I'm confused and need help.
Or in general, do we need to memorize/understand certain half reactions?

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When do we use electrodes (e.g. Pt(s)) for cell diagrams? And why must it be inert?

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If I am referring to the right graph, the flat line is under irreversible, isobaric(constant pressure) conditions where it is defined by w=-P∆V. Lavelle always refers to their being a pin in a piston and once he releases that piston, there is a rapid work of expansion being performed. This is what m...

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Yes, this is because since temperature is constant. The equations, C∆T and mC∆T have a change in temperature, but adiabatic is constant temperature. Therefore ∆U only is dependent on work of expansion, w.

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Essentially, activation energy is the energy required for a reaction to proceed. For example, when you need to strike a match, you need a certain amount of energy in order for the match to be lit. Kinetics is related to how the activation energy changes as a result of a catalyst, temperature, concen...

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Both q and w are considered to be change already. Since heat is flowing between the system and surroundings, there is already a change in heat being transferred/absorbed/released. Same applies for work. Work is a broad term, but it's the merely the idea that something is capable of doing stuff. When...

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It is under viewtopic.php?f=160&t=41732&p=142946&hilit=hotdog&sid=1f229ac698aee2f375c26e18c57782ad#p142946

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Why is it that SO2F2 have 6 possible orientation/microstates, but FClO3 have 4 possible orientations? Is there a method to determine this number?

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There are three places where temperature increases (solids, liquids, and gases). These places where temperature increases utilizes mC∆T where C is the specific heat capacity for water at a certain phase. Then, there are places where temperature does not change and they are phase changes (melting and...

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When can we use PV=nRT and in what conditions? And what is the difference between PV=nRT and P∆V=∆nRT?

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What does a negative and positive delta U value tell us?

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Use the bond enthalpies in Tables 8.6 and 8.7 to estimate the reaction enthalpy for: CH4(g)+4Cl2(g)--->CCl4(g)+4HCl(g). Can someone break down this step for me? I did 4(412)+4(0) - 4(338)- 4(431)=-1428 kJ/mol. However, when I accounted for Cl2(g) being 242kJ/mol, I got the textbook answer of -460 kJ...

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Melting is considered endothermic because heat is required to break the bonds in the solid ice to become liquid water. In a similar vein, heat is required to break the bonds in the liquid water to become gaseous particles. Both processes require an input of energy to allow the molecules to reach a m...

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Was there a reason to know all three methods? Why should one be used than another?

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To add, the bond enthalpy calculation process can lead to inaccuracies in enthalpy values. This is because bond energy between two atoms may be different depending on the bond length/angle. The only guaranteed enthalpy value is with diatomic molecules.

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The pH is given after HClO2 reacted to reach equilibrium. Doing 10^-1.2 gives you the molarities at equilibrium. Hence, you must use an ICE box to create a Ka equation to find the Ka and pKa.

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We use the salt, KNO2, to find the pH of nitrous acid. 1. Dissociate the 0.150M of KNO2, which are K+ and NO2-. Since it's a salt, we can use stoichiometry to find the molarity of NO2-. That will be NO2-. You use that to find the pH of nitrous acid. 2. Since HNO2 (nitrous acid) is weak, it'll underg...

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How does OH- and H3O+ appear to move faster than other ions? I don't understand its connection with autoprotolysis.

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This question has a very small K value being 3.2x10^-34. When doing calculations, it results in this equation: (x^2)/(0.22-x)^2=3.2x10^-34. Since K is very small, could we assume that 0.22-x is 0.22 because the answer will be insignificantly different? This way, I could avoid the quadratic formula a...

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C means the "Change" in a reaction. You will use stoichiometry to figure out these values.From the problems we've done in the textbook, we use "x" to define the change since we don't know the concentration difference from initial to equilibrium. Then, use products over reactants ...

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What he means is that adding a product/reactant will eventually result in the product to reactant ratio to be the same as the equilibrium constant. This, hence, relates to changes in temperature, concentration, and pressure because these are temporary fluctuations in the reaction. The reaction will ...

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Solids and liquids (pure substances) are incompressible and concentration don't change (or change very insignificantly) throughout the reaction. For example, pure water in the liquid or solid phase is 100% water and incompressible. Hence, water doesn't influence the reaction.

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What does a large Kc value mean besides being product or reactant favored? For example 10^7 versus 10^9. Does it have any relationship to kinetics or something else?

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To add, boiling point can also increase with increased surface area, molecular weight, and amount of London Dispersion forces there are. More condensed and bunched up lewis structures contribute to lower boiling points than ones that are more spread out in a hydrocarbon chain.

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Shape is determined by the number of ligands that are attached to the metal ion/atom.

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HSO3- is a good example since it can turn into both an acid or base.

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Do we have to remember the names of the metals when the complex ion is negative?

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How do we know when a coordination complex is a square planar or tetrahedral?

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We know when there are two or more places where a metal atom/ion can bind to the lone pairs of a ligand. You can definitely use Lewis Structures (3D dimensional analysis, too) to understand where the metal will bind.

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When you compare a single bond to a double bond, multiple bonds (double and triple) have a higher electron density region. If you think of it as a small circle, a single bond only has a small circle which can influence around it, and double bonds have a larger circle and a triple bond would be even...

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Can someone tell me the bond angles for NO3- and S2O3^2-? I researched them and it says that the bond angles for NO3- is 120 and S2O3^2- is 109.5.
I thought bond angles change with double/triple bonds, but how come they aren't?

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What it's basically saying is that the diatomic molecule has a certain amount of energy at a particular distance needed to break the molecule apart. All molecules have this optimal distance between each other that is really stable. At this optimal distance, the potential energy is at its lowest due ...

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Borazine, B3N3H6, is a resonance structure that has alternating single and double bonds. This is because of the delocalization of electrons that contributes to the compound's stability. How would we know this without having prior knowledge of "aromaticity" in organic chemistry? My initial ...

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Can someone draw how N2H4 (trigonal pyramidal) would look like with wedges and dotted lines? What would the bond angles be and why?

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Why does shape matter more than electron geometry? And a following question, how does this relate to hybridization?

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What exactly is the purpose of identifying sigma/pi bonds in molecules?

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There isn't necessarily a rule for that, but you can identify many things, such as symmetry (symmetry=nonpolar, asymmetry=polar), electronegativity, and shape.

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Van der Waals are transient intermolecular forces, meaning that the interactions between molecules are temporary and do not last long. Van der Waals are found everywhere. Hydrogen bonds are a stronger intermolecular force because of the difference between electronegativities. For example, water has ...

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The names of the two are synonymous (Van der Waals= London Disperson Forces). They are both intermolecular forces found everywhere. They occur when an electron cloud of one atom is heavily dense, while the other doesn't have a lot. This creates a temporary attraction between each other that are rela...

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Yes it does because lone pairs want to be closer to the nucleus in comparison to a bonding pair. When this happens, the lone pairs take up more space due to the repulsion between each other. Hence, the geometric shape is important because it shows the shape that minimizes the repulsion between elect...

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Yes, I use that same formula as well. The 1/2 part in the formula is just used to account for the bonds. Your formula works just the same.

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When you go from a higher shell to a lower one (n=3 to n=1, Lyman series), then delta E is negative. Conversely, when it is the opposite way, then delta E is positive. I think it is essential to note this difference in sign because it tells you about the excitation of the atom. I did a practice prob...

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Is it necessary to check if the Lewis structure is the best one by determining the formal charge of each atom? For example, when COCl2 has a double bond with oxygen and the rest have single bonds, then all formal charges equal 0. But when there is a double bond with Cl, then it begins to change. If ...

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Cl^2- because of the bigger proton count. Since they are isoelectronic (where they both achieve the noble gas configuration), you should look at which has more protons to attract the negatively charged electrons. This will, consequently, lead to a smaller radius.

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Ionic bonds are generally stronger than covalent bonds in non-aqueous environments because of the big difference in electronegativity between the metal and nonmetal, leading to the transfer of electrons towards the more electronegative atom (e.g. NaCl). Covalent bonds (polar and non polar) have less...

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This is because of the Aufbau principle, which basically states that the orbitals/numbers must go in numerical order in simple terms. Since Thorium is in the 5f orbital, it will not be included in the shorthand/noble electron configuration you have given.

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What do the different orbitals (s, p, d, f) mean and its relationship with the periodic table? For example, n=3.

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When a principal quantum level decreases down (e.g. n=4 to n=3, a Paschen series), how come the delta E would not become negative?

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As you move from the bottom left to the upper right corner, the atomic radii decreases/becomes smaller. As you go up the group, the shelling effect decreases. Each shell decreases the attraction of the nucleus to the electrons. Going right across the period increases the proton number, thus increasi...

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It demonstrated that the classical model was not working. Scientists thought that increasing amplitude would increase kinetic energy. However, it was light's frequency that increased kinetic energy. Long wavelength and high intensity light doesn't necessarily result in electron ejection.

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1 meter has 1,650,763.73 wavelengths. If you divide it, you will get 6. 0578x10^-7. This number means that in one wavelength (trough to trough) it is equivalent to 605.8nm. I do not think that energy was a variable to be considered in the problem. For part two of your question here is the math: c=λv...

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Can someone explain to me the relationship between the two equations E=hv and c=λv? How are they different?

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The solution manual was confusing for me to understand, so I did this. Is this a proper/viable way to solve it?

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According to one of the module questions we have done, chemical equations are a shorthand representation of chemical reactions. I believe that it is fine to keep your simplified version because it still demonstrates what is truly happening in the reaction.

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1. Balance the equation. PCl3 + 3H20 --> 3HCl + H3PO3
2. Convert PCl3 to to moles. (23.6g)/(137.32g)= .172 mol of PCL3
3. Use stoichiometry .172 mol(3 mol HCL)= .516 mol HCL
4. Convert .515 mol HCl to grams. .516mol(36.46g)= 18.8g HCl

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