CHEMISTRY COMMUNITY

Riddhi Mehta 2C

I believe the units for A would be the same as the units for the rate constant k. This is because if you solve the equation for Ea, the result would be: Ea=-RTln(k/A). The units for activation energy are J/mol, and the units for R*T are also J/mol, which would mean that the units for A would have t...

Riddhi Mehta 2C

Can a catalyst be part of the overall rate law or does it need to be substituted out like an intermediate?

Riddhi Mehta 2C

Like people have mentioned above, the intermediate is not in the overall rate law, even if it is in the slow step. You have to substitute it with other reactants that are not intermediates. I believe Professor Lavelle will be teaching us the method to do that during tomorrow's lecture. I think it wa...

Riddhi Mehta 2C

Thus far, we have learned that the reactant in the overall rate law are the reactants in the slow step. Basically looking at the overall reaction tells you what the reactants are for the slow step equation.

Riddhi Mehta 2C

An intermediate is a species in the reaction that is created as a product and then consumed in another step. It does not appear in the overall reaction.

Riddhi Mehta 2C

Does a catalyst affect the rate constant? I know it affects the rate but does it affect the rate constant and if so, how?

Riddhi Mehta 2C

Since this is a galvanic cell, we know that this reaction has to have a positive standard potential in order to function as a galvanic cell. Therefore looking at the standard potentials in the chart, we can determine which one would be the anode and the cathode since only match gives us a positive s...

Riddhi Mehta 2C

I feel the same as well. I have been so stressed out over this final but I have been trying to go to all the review sessions I can. I think working through the textbook problems and going back through the sapling homework also will be good review as other people have suggested!

Riddhi Mehta 2C

I believe it can be if all the reactants in the reaction are zero-order. The overall order of the reaction is simply based on all the reactants so if each reactant order is zero then the order would be zero and I guess the rate law would only depend on the rate constant.

Riddhi Mehta 2C

What are the units for the frequency factor, A, in the Arrhenius equation and what information do we need to solve for it?

Riddhi Mehta 2C

How would we solve for the frequency factor? I understand what it is but what is the information we need to solve for it?

Riddhi Mehta 2C

A catalyst is a reactant that does not show up in the overall reaction. It is used up in one of the steps and is essentially the opposite of an intermediate. It is used up as a reactant and is reformed as a product.

Riddhi Mehta 2C

From a lot of the other posts on here, I believe if the formatting isn't the issue or if it seems right, try moving around some of the species. The order of the species in the equation is causing an error on Sapling for some people.

Riddhi Mehta 2C

I agree with the other responses on here. The species gaining mass is the cathode and the species losing mass is the anode. Also if you are feeling super confused looking at just the equation, try removing everything that is not a solid and going from there. It might be easier to be looking at only ...

Riddhi Mehta 2C

To add on a bit more, make sure to include the aqueous solutions right next to the salt bridge on either side (so next to the double lines) to show that those are the molecules that are travelling through the bridge.

Riddhi Mehta 2C

Yes, I definitely agree with this. I put OH- at the end of the the reactants and it finally worked. Also make sure that you have all your phases in.

Riddhi Mehta 2C

I did not have the same exact problem, but just make sure to check that the charges on either side are also balanced out. Both sides should be equal. If not, a couple of questions in Sapling are being weird so I would suggest you try switching around some of the species.

Riddhi Mehta 2C

Monatomic ions simply consist of one ion. In the equation provided however, there are no monoatomic ions because all the molecules have multiple atoms.

Riddhi Mehta 2C

Crystal Pan 2G wrote:You should try deleting the parentheses. I had the same answer except without the parentheses.

Thank you so much! I knew I was doing it right, but it kept telling me I was wrong. I finally got it when I removed the parentheses.

Riddhi Mehta 2C

I have been having these problems as well and I cannot seem to figure out number 18. I am pretty sure my answer is correct but I am not sure why it is not accepting it. I even tried changing up the way I wrote the equation to no luck.

Riddhi Mehta 2C

The salt bridge is to keep neutrality in both the solutions or else there would be a positive and negative side in the circuit. I also believe that without the salt bridge, the circuit wouldn't run because it would not be closed.

Riddhi Mehta 2C

To figure out basic conditions, you would essentially just follow the same steps as acidic conditions and add OH- to both sides to cancel out the H+ and turn them to water molecules. The steps outlined in the responses above are very helpful!

Riddhi Mehta 2C

I think another thing you can try is copying and pasting a value with a subscript and seeing if that works. If not, I would highly suggest contacting your TA or the technical team at Macmillan.

Riddhi Mehta 2C

Entropy is the measure of disorder or level of chaos in a system whereas enthalpy is the energy in the system.

Riddhi Mehta 2C

Yes, as the replies show, the equation is Cp = Cv + R and since Cv is 3/2R then that makes Cp = 5/2R for ideal gas conditions.

Riddhi Mehta 2C

I understand that q = delta H when there is constant pressure but if there is constant pressure and constant volume, does that mean q = delta H = delta U? Is this even possible? Can someone give me a specific example?

Riddhi Mehta 2C

An isolated system is pretty much impossible to create because there is no such thing as perfect insulation where nothing goes in or out. However, we study it because it provides us with an understandable version of how the world works around us. It is very similar to why we study things with no fri...

Riddhi Mehta 2C

Hi! I am a bit confused on how to answer this question. For a particular reaction, ΔH∘=−93.8 kJ and ΔS∘=−156.1 J/K. Assuming these values change very little with temperature, at what temperature does the reaction change from nonspontaneous to spontaneous? How do you know when a rxn goes from nonspon...

Riddhi Mehta 2C

You can add substances and substances can leave an open system (like water evaporating) and energy can move in and out, but in a closed system only energy and work can act upon it. If you want a visual, there is a really good one in Dr. Lavelle's Lecture #10.

Riddhi Mehta 2C

A closed system just means that no substance can go in and out. However it is not insulated like an isolated system. A closed system still allows transfer of heat and energy. If you want a visual, I suggest to go back to Dr. Lavelle's Lecture #10 as there is a great graphic there showing the differe...

Riddhi Mehta 2C

I think you would use q = mcΔT whenever the c given is the specific heat capacity. The units of c would then be kJ/g°C. If you were given the molar heat capacity with the units of kJ/mol°C, then you would use the equation q = ncΔT instead. Oh, that makes sense. Thank you, I didn't realize the diffe...

Riddhi Mehta 2C

Hi! So when you solve for chemical equilibrium problems, you do not include solids or liquids. Therefore, you would ignore the reactant that was a solid for that question. To find the total pressure, you would just have to add up the partial pressures of the products once you solve for them. I do n...

Riddhi Mehta 2C

Yes, the specific heat of water shows that with each change of unit in temperature (Celsius or Kelvin) in one gram of water, either 4.184 J is absorbed or released by the water.

Riddhi Mehta 2C

I know that the heat equation is q = mcΔT where m is in grams. However, today my TA used the equation q = ncΔT where n is moles. I was wondering how to tell when to use either equation and what exactly the differences are between the two. Thank you!

Riddhi Mehta 2C

Since one unit of change in Celsius is the same as a one unit change in Kelvin, then you can use the change in temperature in either unit interchangeably. Just make sure to check the units in the problem you are solving to be safe.

Riddhi Mehta 2C

I agree with the previous answers. Enthalpy is a measure of heat content and entropy is the measure of chaos in a system. Enthalpy is signified by the variable H and entropy by the variable S.

Riddhi Mehta 2C

From what I have seen, you usually use this equation when calculating for a system that is allowed to expand reversibly. Also another equation that is the same but doesn't use an integral is w = -nRTln(v2/v1)! If you have all the information, this equation might be easier to use.

Riddhi Mehta 2C

Hello! This is question #19 from week 3 & 4 homework. I am just a bit lost on where to start. A constant‑volume calorimeter was calibrated by carrying out a reaction known to release 1.56 kJ of heat in 0.700 L of solution in the calorimeter (q=−1.56 kJ) , resulting in a temperature rise of 3.34 ...

Riddhi Mehta 2C

Hi! I am not sure if we will have to use the equation with the integral but another equation that is equivalent to the one with the integral is
w=-nRTln(v2/v1).

To answer your second question, yes!

Riddhi Mehta 2C

I agree with everything that has been said. Yes, you can use all three methods to figure out the enthalpy of a reaction. If given the enthalpy of formation of molecules, you can also figure out the bond enthalpy for a certain molecule.

Riddhi Mehta 2C

Does vapor usually refer to water or can it refer to any other element as well?

Riddhi Mehta 2C

When you look at the phases of water diagram, the flat line between where the liquid phase ends and the gas phase begins is all the energy that goes into water becoming steam. All that energy is turned into kinetic energy which causes the motion and excitement of the water molecules. So when steam t...

Riddhi Mehta 2C

I also originally had trouble with this question but I realized it was seeing if we understood that breaking bonds requires energy and forming bonds releases energy. So basically if the product formed was ranked lower than the reactants that were broken then it is endothermic.

Riddhi Mehta 2C

It is the net change in enthalpy. You can apply it by adding or multiplying different reaction enthalpies to figure out a problem.

Riddhi Mehta 2C

It can also be shown as J/g*K due to the interchangeable units!

Riddhi Mehta 2C

Since the change in units of Kelvin and Celsius would be the same (meaning a change in temperature of 12.3 Kelvin is the the same as 12.3 Celsius), then the units are interchangeable in specific heat. You just use the one unit that is provided in the question. Hope that helps!

Riddhi Mehta 2C

Yes, enthalpy of formation refers to only one molecule being formed. Since there are two products in this reaction is cannot be the enthalpy of formation for both, instead it would be the standard reaction enthalpy. Also we know what a combustion reaction equation looks like so that is why it is con...

Riddhi Mehta 2C

I agree with everything that has been said above. This also relates to why being burned by steam is worse than boiling water because due to that flat portion, there is a lot more kinetic energy in the steam. The gas moves around faster than boiling water even though they are at the same temperature ...

Riddhi Mehta 2C

Yeah, you basically just memorize all the strong acids and bases listed in the textbook. To remember bases, I just look at the second column of the periodic table. Everything else is considered a weak acid or base.

Riddhi Mehta 2C

In order to solve the question presented below we need to know the Ka value for the acid. I know this is a strong acid so it pretty much completely dissociates but the table (Table 6E1) only says that the Ka is strong. What value represents a strong Ka?

Calculate the pH of 0.15 M H2SO4(aq) at 25 °C.

Riddhi Mehta 2C

Hello! I am a little confused on how to go about calculating the Ka and pKa values. I know I need to create an ICE table and figure out the molar concentration of the substance but I am not able to get the answers the solution manual provides. Any insight would be very helpful! When the pH of 0.10 M...

Riddhi Mehta 2C

Yes! The standard enthalpy of any element in its standard state is 0, but like it is mentioned above, we only need to know a few.

Riddhi Mehta 2C

I believe we also need to know whether a salt is considered basic or acidic. Mostly though, it is a smaller subject under equilibrium for this class.

Search found 53 matches