CHEMISTRY COMMUNITY

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What is microscopic reversibility? I’m confused on how it applies.

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Why are anodes connected to external circuits?

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For small time intervals why can’t we use the average rate?

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What do catalysts specifically do to speed up reactions?

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The idea behind this problem is that Ea(forward) - Ea(reverse) = E(products) - E(reactants) = delta H. If you rearrange the equation, Ea(reverse) = Ea(forward) - delta H, and plug in the values, you should get your answer. Ea(reverse) = 33 - (-39) = 72 kJ The amount of activation energy is related t...

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I believe once you find the order of each reactant, the sum of the orders will give you the overall order of the reaction.

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Hi! What you have to look at is which 2 experiments have the same initial concentrations, and have only 1 difference between the 2 experiments you are comparing (rates don't have to be the same). You need to be able to cross off most of the values so you are left with rate = [#]^n, let's say. Once y...

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Hi, This problem gives you the uncatalyzed and catalyzed reaction rate for an equation, and the activation energy for them. The question is to "Determine the factor by which the catalyzed reaction is faster than the uncatalyzed reaction at 299.0 K if all other factors are equal." I used t...

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The Arrhenius equation is k = Ae^(-Ea/RT). Since we are looking for Ea, we have to isolate it. We divide each side by A, and take the ln of both sides to get rid of the e. This will leave us with ln (k/A)= -Ea/RT. Isolate the Ea and get Ea = -RTln(k/A). You can plug all the values in now, but make s...

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The equation I used for this problem is ln[A]t / [A]0 = -kt because it connects concentration to first-order reaction. [A]0 is the initial concentration and [A]t is the concentration at a given time. Since we are solving for t, you would isolate t to get t= (ln[A]t/[A]0) / -k, and plug in all the va...

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Screenshot 2023-03-12 at 22.55.47.png I tried this problem several times (also according to its feedback), but I still could not get the correct answer. Can someone please help me? I got my current answer by e^{-61000/(297*8.314)} / e^{-122000/(297*8.314)}. Maybe try using kj instead of J. Don't kn...

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Hi, I was really confused regarding this question. I know that we use the equation k=Ae^-Ea/RT, however I keep getting the question incorrect and I was wondering if I could get any help.The presence of a catalyst provides a reaction pathway in which the activation energy of a reaction is reduced by...

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Yes, E॰ is intensive because it is in the standard form. While normal E (cell potential) is an extensive property because it depends on the amount of substance.

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So we know the slowest step is 2) because it is given in the question. We use the slowest step because that determines the rate of the reaction (takes most amount of time). The rate law for the slowest step is rate= k[HClO][I−]. But we see that HClO is used as an intermediate (product in step 1 and ...

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Do the 4 additional responses have to be for questions that no one has replied to? Does the extra credit still count if we post under questions that already have responses? Can we add more?

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Audric Banuelos 1A wrote:By the end of week 10. Or 34 (4 extra great responses) by the end of week 10 to get extra credit.

Do the 4 responses have to be questions that have no response? Or do they count even if there is a couple responses already?

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An intermediate is produced then consumed. In step 1, ABC is produced so it is on the products side. Then in step 2, it is consumed/used as a reactant. A catalyst is consumed then produced. In step 1, A is used up as a reactant, but in step 2, it is produced as a product. Both intermediates and cata...

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Yes, I believe so. Only when the forward and reverse rates are equal is when we can say the reaction is at equilibrium. This is because the reaction uses the same pathway (same intermediates) to go from R --> P as it does for P --> R. This means the concentrations of reactants and products remains f...

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Hi Ava! It is also important to understand that temperature affects the rate constant. If temperature increases, that usually means the reaction will speed up. This all goes back to the Arrhenius equation that relates the rate constant to the activation energy and temperature of the reaction. Since ...

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Hi! The instantaneous rate is actually the slope of the tangent line, which is the red line on the graph. Therefore, to find the slope of any line, you can technically choose any of two points from the table. You can plug in any of the values into (Y2 - Y1) / (X2 - X1). So it really doesn't matter w...

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Hi! So we know the general rate law equation is written as: rate=k[A]^a[B]^b[C]^c We basically have to plug in values from the table to isolate each exponent at a time because a, b, and c tell us the reaction orders of each reactant. Therefore, we need to compare the values from 2 experiments at a t...

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I thought of it as like those "systems of equations" from high school, for example we have 3 equations and 3 variables to solve. In this case, we need to solve for n, m, and l, the orders of reactants A, B, and C respectively. We can take the ratios of 2 experiments' experimental values t...

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I think we care about the Arrhenius equation because it relates the rate constant to activation energy and temperature. We did not cover exactly where it comes from since we did not derive it and we don't need to know how to derive it. Also when we take the ln of the equation we can get a linear re...

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For the reversible, one‑step reaction, A+A⥫⥬=k−1k1B+C the rate constant for the forward reaction, k1, is 275 L⋅mol−1⋅min−1 and the rate constant for the reverse reaction, k1, is 381 L⋅mol−1⋅min−1 at a given temperature. The activation energy for the forward reaction is 40.6 kJ⋅mol−1, whereas the act...

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When do we use the Arrhenius equation? Can someone please explain the logic behind it and where it's from? I am not sure when and why we use it.

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The mechanism proposed for the oxidation of iodide ion, I−, by the hypochlorite ion, ClO−, in aqueous solution is shown. 1) ClO−(aq)+H2O(l)⇌HClO(aq)+OH−(aq)fast in both directions 2) I−(aq)+HClO(aq)→HIO(aq)+Cl−(aq) slow 3) HIO(aq)+OH−(aq)→IO−(aq)+H2O(l) fast Complete the rate law for the formation o...

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For the reaction 2A(g)+2B(g)+C(g)⟶3G(g)+4F(g) the initial rate data in the table was collected, where [A]0, [B]0, and [C]0 are the initial concentrations of A, B, and C, respectively. 1) Identify the order of reactant A. 2) Identify the order of reactant B. 3) Identify the order of reactant C. 4) Wh...

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The rate of the given reaction is 0.240 M/s.

A+4B⟶2C

What is the relative rate of change of each species in the reaction?

How do I go about solving this? I have no idea where to begin. Can someone please explain? Thank you!

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Joyce Lee 1K wrote:Hello! For this question, I believe you may have looked at the wrong standard reduction potentials because from my understanding the equation should be 2.356-(-0.34) = 2.696. Hope this helps!

Oh thank you so much for your help!

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A galvanic (voltaic) cell consists of an electrode composed of magnesium in a 1.0 M magnesium ion solution and another electrode composed of copper in a 1.0 M copper(II) ion solution, connected by a salt bridge. Calculate the standard potential for this cell at 25 °C. Refer to the list of standard r...

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Hi there, The first step would be to break down each into half reactions. I will use the first problem as an example as they have the exact same methodology. The half reaction for Cl2O7 first becomes Cl2O7(g)⟶2ClO−2(aq)+3H2O(l) to balance the oxygen atoms. Then the completely balanced half reaction...

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For the first reaction I'm getting:

Cl2O7 + 2OH + 4H2O2 --> 2ClO2 + 4O2 + 5H2O

But achieve is counting it wrong. Is this not correct?

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Identify the oxidizing and reducing agents in the skeletal (unbalanced) reaction. Then, balance the reaction, including the phase (solid, liquid, etc.) of each species. The reaction takes place in basic aqueous solution. Cl2O7(g)+H2O2(aq)⟶ClO−2(aq)+O2(g) Pb(OH)2−4(aq)+ClO−(aq)⟶PbO2(s)+Cl−(aq) Hi! Ca...

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Write a balanced chemical equation for the formation reaction of (a) NH3(g); (b) H2O(g); (c) CO(g); (d) NO2(g). For each reaction, determine H, S, and G, from data in Appendix 2A. For this problem, do the coefficients in the balanced equation have to be fractions? I tried simplifying it to make it w...

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Will the molecular structures be given for bond enthalpy problems?

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How would you approach part b of this problem? All the components are given but I do not know where to begin.

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Hi! For this problem, you are looking for the final temperature. Adding the ice to water will increase the temperature of the ice and decrease the temperature of the water. One thing to keep in mind is that before the temperature of the ice is increased, it needs to change from ice to water. The ge...

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An ice cube of mass 50.0 g at 0°C is added to a glass containing 400.0 g of water at 45°C. What is the final temperature of the system (see Tables 4A.2 and 4C.1)? Assume that no heat is lost to the surroundings.

How do I approach this problem?

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(a) At its boiling point, the vaporization of 0.579 mol CH4 (l) requires 4.76 kJ of heat. What is the enthalpy of vaporization of methane? (b) An electric heater was immersed in a flask of boiling ethanol, C2H5OH, and 22.45 g of ethanol was vaporized when 21.2 kJ of energy was supplied. What is the ...

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Mehreen_Suzaan_1A wrote:So when you calculate your work, the problem does not imply any need for heat so delta u would be equal to just the work since there is no heat (q), therefore what you calculated for a would be your answer for c!

But the book says the answer for part c would be 8J

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A constant-volume calorimeter was calibrated by carrying out a reaction known to release 3.50 kJ of heat in 0.200 L of solution in the calorimeter (q=-3.50kJ), resulting in a temperature rise of 7.32°C. In a subsequent experiment, 100.0 mL of 0.200 M HBr(aq) and 100.0 mL of 0.200M KOH(aq) were mixed...

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Air in a bicycle pump is compressed by pushing in the handle. The inner diameter of the pump is 3.0 cm and the pump is depressed 20. cm with a pressure of 2.00 atm. (a) How much work is done in the compression? (b) Is the work positive or negative with respect to the air in the pump? (c) What is the...

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For (a) you would want to: 1) NH3 + H2O <-> NH4+ + OH- then do an ice table I 0.057 M 0 0 C -x +x +x E .057 x x ignore x since Kb= 1.8e-5 is small Then do K = x^2/.057 and solve for x which is equal to the concentration of OH-. then do -log[OH-] = pOH and you can find pH from 14-pOH. Hope you can s...

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I seem to be getting the wrong answer but I am not sure what I am doing wrong. Can someone please explain how they would solve this? A student added solid Na2O to a volumetric flask of volume 200.0 mL, which was then filled with water, resulting in 200.0 mL of NaOH solution. Then 5.00 mL of the solu...

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The two air pollutants SO3 and NO can react as follows: SO3(g) + NO(g) --> SO2(g) + NO2(g) (b) Given that at a certain temperature K=6.0*10^3, calculate the amount (in moles) of NO that must be added to a 1.00-L vessel containing 0.245 mol SO3 to form 0.240 mol SO2 at equilibrium. Can someone please...

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Can someone please explain how to solve this problem? I was not able to attach the graph, but it is 5.35 in the textbook. Thanks! The following plot shows how the partial pressures of reactant and products vary with time for the decomposition of compound A into compounds B and C. All three compounds...

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I am a bit confused about this too. Can someone explain it with the context of Achieve #3? I am getting a percent ionization greater than 5%.

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I was wondering if the audio visual focus topics were mandatory to do? If not, how helpful were they?

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205722709 wrote:How many times do we have to post or reply on here to get full points?

3 times a week I believe

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How do I begin to tackle this problem? It is #5 on the Achieve homework Consider the reaction of NH3 and I2 to give N2 and HI. 2NH3(g)+ 3I2(g) <---> N2(g)+ 6HI(g) K Using two or more of the given equations, determine the equilibrium constant, K , for the reaction of NH3 with I2. H2(g) + I2(g) <---> ...

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I was just wondering around what week we will get into thermodynamics?

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Can someone briefly explain Le Chatelier’s principle? What is the relationship between concentration and pressure, and why does that not change K?

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Hi! Can someone reiterate the difference between K and Q? How do they each relate to the product/reactant ratio?

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