CHEMISTRY COMMUNITY

TiffanyL1G

I think the slowest elementary step determines the molecularity of the reaction, but if a molecule in the previous fast equation were to cancel with a molecule in the slow equation. Would that molecule still be used to determine molecularity? For example: A\rightleftharpoons 2B (Fast) 2B + C...

TiffanyL1G

In the sixth edition textbook, the problem provides the rate laws derived from elementary steps and asks you to draw a proposed structure for the activated complex. What is the activated complex and how does one draw a proposed complex? For example, part c od the problem provides: "Rate = k[O2]...

TiffanyL1G

How does one solve for A, the frequency factor, in the Arrhenius Equation? I think Dr. Lavelle said we wouldn't have to solve for A and we just have to assume it is 1 for this class. Is that true? If not how does one solve for A?

TiffanyL1G

Is it possible to have fractional rate constants? Should we round up/down to the nearest whole number or do we just take the natural log and solve for the rate constant?

TiffanyL1G

Can someone explain in simpler terms what the unique average rate is, why we use it, when to use it, and when not to use it? What qualities affect the rate and what qualities do not?

TiffanyL1G

What is the difference between instantaneous rate and average rate?

TiffanyL1G

In class, Dr. Lavelle listed three different ion-selective electrodes (H+, Na+, and K+). Are these three the most popular and only ion-selective electrodes or are there other ion-selective electrodes?

TiffanyL1G

Can someone give step to step instructions and an example of how balance half reactions in a basic solution? I know you're supposed to balance the element first, then the oxygens, hydrogens, and finally electrons. I don't understand why I have to add water on the same side as OH- because then both s...

TiffanyL1G

What are the differences and similarities between a salt bridge and a porous disk?

TiffanyL1G

In the cell diagram Dr. Lavelle always draws on the board, what exactly does the salt bridge do?

TiffanyL1G

When we are writing out the 1/2 reactions, why do we always write our redox reactions as reductions and not oxidations? Is it possible to solve the same problem but with oxidations reactions?

TiffanyL1G

The reduction potential is usually given to us as E°, but if we were even given the oxidation potential would it be the negative value of the reduction potential?

TiffanyL1G

When calculating work under constant pressure the equation is w=-P delta V and can often be substituted as -delta nRT. When we solve for n do we only consider the molecules in the gas phase or do we include all molecules in any phases?

TiffanyL1G

Which constant is for monoatomic, diatomic, linear, and nonlinear?

TiffanyL1G

Is S=nCvln(T2/T1) used only for the calculations of an ideal gas and is S=nRln(V2/V1) used only for the calculations of a gas?

TiffanyL1G

Is there such thing as nonexpansion work, and if so how would one calculate that?

TiffanyL1G

Why and how is $\Delta$ U a state function but q and w are not?

TiffanyL1G

Can someone explain to me in simple terms what's the difference between reversible expansion and irreversible expansion? Which would do the most work, and why?

TiffanyL1G

Dr. Lavelle mentioned that for Cp you can refer to the ideal gas law PV=nRT, where the number of moles, n, and the universal gas constant, R, would remain unchanged, but the temperature, T, would increase and would, therefore, increase the overall Volume. Work is happening for Cp.

TiffanyL1G

I'm a little confused on what is the difference between enthalpy and heat capacity. Can someone explain to me what the differences are, and what would be the ideal temperature unit to use for them?

TiffanyL1G

Do standard enthalpies only apply for gases? Is it like equilibrium, where any solid or liquid molecule in a chemical equation is ignored? Is it the same reason as equilibrium?

TiffanyL1G

In the 6th Edition textbook problem 12.79, they give us a strong acid as the starting molecule. Due to the fact that it is a strong acid am I suppose to assume that because it can fully disassociate I will have to the ICE Table on the second ionization equation? Also when I am solving for the initia...

TiffanyL1G

What type of values can the ICE Table calculate? I know the ideal "units" is concentration, but I was also told that you can do moles and just divide everything by the volume after. I also know that you can use bars in the ICE Table, so is there any sort of value or measurement that we sho...

TiffanyL1G

Deprotonation is when you add water to any molecule in a chemical equation and the product becomes H+/H3O+ with the conjugate base. When you solve for percent deprotonation, it is the concentration of the H+/H3O+ divided by the initial (given) concentration multiplied by 100%.

I hope this helps.

TiffanyL1G

You don't use solid or liquids when calculating the equilibrium constant because solids and liquids are pure. They do not have a concentration, and if they do not have a concentration then they are not included in the calculations for K and Q.

TiffanyL1G

When solving equilibrium problems is there a preferred temperature unit we should be using? I noticed in some homework problems that they use Kelvin and Celcius, should we be converting one of them or does it not matter?

TiffanyL1G

In the 6th Edition textbook problem 11.39, the problem gives the reaction 2BrCl(g) + H2(g) \rightleftharpoons Br2(g) + 2HCl(g) and hints for us to use Table 11.2 for help. From there I noticed we had to add two different equations to form the given reaction. How exactly do you add the two equations ...

TiffanyL1G

Why is it that when solving for Q, the reaction quotient, we disregard the solids and the liquids in the chemical equation? I think we disregard solids because it isn’t possible to find the concentration of a solid but why do we disregard liquids?

TiffanyL1G

K is also known to be the composition of the reaction mixture at equilibrium at a given temperature. Kc is used for substances with concentration (Aqueous and or if there is more than one form in the chemical equation), and Kp is used for partial pressures that have gaseous compounds.

TiffanyL1G

What is the reaction Quotient and how does one solve for that? For example in the 6th edition textbook, problem number 13a, how would you solve for that problem?

TiffanyL1G

Is the only way you can determine if a compound is amphoteric is if it is located near that diagonal band of metalloids?

TiffanyL1G

How do I determine if a ligand is polydentate? Is the only method drawing out the ion? In the 6th edition #17.33 why is [CO3](2-) only able to have 1-2 bonding sites, I thought a bonding was possible as long as there were lone pairs?

Why is water always a monodentate ligand?

TiffanyL1G

So for 31b the name is "pentaamminesulfatocobalt(III)" which the solution manual gives [Co(NH3)5(SO4)]Cl what happened to the 3? Does it go to Cobalt or Chloride? I had the same issue with part d which is "sodium bisoxalato(diaqua)ferrate(III)" and the solution manual gives Na[Fe...

TiffanyL1G

Can someone explain in simpler terms what diamagnetism and paramagnetism is? The book definition is a little confusing. Thanks!

TiffanyL1G

What does the solution manual mean when it states "However, because C atom is involved in a double bond and the N single bond radius gives 142pm, which is close to the experimental value of 133pm"? I thought the bond length for CN would just be 77pm +75pm=152pm. Why does it suddenly talk a...

TiffanyL1G

How do you determine when the largest dipole moment is for a molecule?

TiffanyL1G

How do you write pi bonds on the molecule? I understand how to identify them, but I don't understand how to write the composition of the bond and the hybridization of a pi bond? For example on problem #95 (in the 6th edition chapter 4), in part b the problems asks that you write the composition of t...

TiffanyL1G

In the 6th Edition of the Chemical Principles book the textbook draws a Lewis Structure that gives Boron a double bond with Nitorgen when it does that doesn't it give Boron a -1 charge? But the initial molecule does not have a charge so shouldn't we just draw a lone pair on each Nitrogen? Does this ...

TiffanyL1G

In the 6th Edition of the Chemical Principles Textbook, the question states "Noting that the bond angles of an sp3 hybridization atom is 109.5 degrees and that of an sp2 hybridization atom of 120 degrees, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-...

TiffanyL1G

Can someone describe in simpler terms what rule 3 is talking about? The textbook says, "All regions of high electron density, lone pairs, and bonds, are included in a description of the electronic arrangement, but only the positions of atoms are considered when identifying the shape of a molecu...

TiffanyL1G

In the textbook rule 2 states, "There is no distinction between single and multiple bonds: a multiple bond is treated as a single region of high electron concentration." What exactly does it mean? Does that mean a single bond is simply a region with lower electron concentration? Does the e...

TiffanyL1G

How many names and shapes of molecules are we expected to know? Are we expected to memorize these?

TiffanyL1G

Can someone explain in simple terms what is distortion and how it affects polarization? Also, could you define polarization in simple terms? Thanks!

TiffanyL1G

What are the units used for Dipole Moment? I know the equation is dipole moment (mu) = charge (q) x distance between atoms (bond length) [d], but what exactly does this measure and what units are each variable?

TiffanyL1G

Can someone explain in simple terms what exactly does dipole mean and what is a dipole moment?

TiffanyL1G

How do you know how many valence electrons are in the d orbitals, since 4s2 is technically the "outer most" orbital? Would all d orbital elements be either one or two depending on 4s? Or do we add the d orbital and the s orbital together? For example, would Iron (Fe) have six valence elect...

TiffanyL1G

Thanks for answering the second part! But for the first part I was confused on the example he gave for sulfate, (SO4)2-. I know that sulfate has a negative charge of 2 electrons, so I thought the most stable condition would be when the Formal Charge equals minus 2. Or is it when it equals 0? I remem...

TiffanyL1G

An atom or molecule is the most stable when the formal charge of the lowest ionization energy atom is 0? Or does the whole entire molecule have to equal 0? Is it safe to only check the lowest ionization energy atom is zero (when determining if it is in a stable state) or should I check each individu...

TiffanyL1G

I am a bit confused about the stable condition and the equation used to calculate it. Is a molecule or atom the most stable when it's Lewis Structure is equal to zero or is it the most stable when it is equal to the charge? Like for [SO4]2-, is the molecule most stable when the Lewis Structure is eq...

TiffanyL1G

Could someone explain why there isn't a trend for covalent radius?

TiffanyL1G

What exactly is Z and how does it come into play for the effective nuclear charge? The equation given is En= - Z^2 eff hR/n^2, can someone explain what this equation is used for and what it means?

TiffanyL1G

In professor's Lavelle's lecture he stated that n= energy and size aka shell, l= shape aka angular momentum, ml= orientation aka magnetic quantum, and ms= magnetic spin, but are there alternative names? I was reading some of the textbook problems, and they ask for subshells or principle quantum numb...

TiffanyL1G

For the p-orbital there are the px, py, and pz atomic orbitals, but what are the five different orbitals for the d-orbital? What about the f-orbital? Do we only need to know the p atomic orbitals or do we need to know all of them to some extent?

TiffanyL1G

What are the units used for Schrodinger's Equation and what information is needed in order to solve for it?

TiffanyL1G

What exactly is the Stefan-Boltzmann law, when should one use it, and how does one use it?

TiffanyL1G

The question is " A 1.50-g sample of metallic tin was placed in 26.45-g crucible and heated until all copper had reacted with the oxygen in air to form oxide. The crucible and product together were found to weight 28.35g. (a) What is the empirical formula of the oxide? (b) Write the name of the...

TiffanyL1G

Is there such a thing as negative energy? Why is it that during the lecture today when delta E= -4.09 x 10^19 J, we discarded the negative when plugging in delta E into De Broglie Equation?

TiffanyL1G

My TA said you could do any 7 problems from any of the assigned problems on the syllabus, but it would be best to follow what Professor Lavelle had just lectured on.

TiffanyL1G

If not given the work function, how do I calculate for that? What information is needed in order to calculate the work function if not given?

TiffanyL1G

When calculating for the empirical formula, you must first calculate for the limiting reactant. The part I am confused on is how do you know what number to multiply by when your number isn't whole? For example, if you have 100 grams of H2O and you divide by 18g/mol of H2O (the molar mass) your final...

TiffanyL1G

Can someone please explain how naming simple compounds work? I'm a bit confused when to use -ate, -ide, -ous, -ic, and -ite. Do we have to memorize these?

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