CHEMISTRY COMMUNITY

Wilson Yeh 1L

The answer is that the overall reaction is ClO- + I- --> IO-

How come Cl- isn't included with the products?

Wilson Yeh 1L

Elementary reactions basically make up an overall non-elementary reaction. Elementary reactions only involve a single step, whereas non-elementary reactions make up multiple single step elementary reactions. It should be noted that when dealing with elementary reactions, the coefficients DO matter f...

Wilson Yeh 1L

The slow step is the rate determining step, so I think if you were to test a given set of steps, whichever one comes out to work and match the observed rate would be the slow step. At least that's what I'm pretty sure is the case, if I'm wrong someone feel free to correct me!

Wilson Yeh 1L

During lecture today, Dr. Lavelle went over a problem that involved identifying the correct mechanism according to the experimentally determined rate law. I understand everything about the problem, but I'm just curious about what happens if the tested step matches the observed rate. Like during lect...

Wilson Yeh 1L

Sulfuryl chloride, SO2Cl2, decomposes by first-order kinetics, and k = 2.81 x 10 -3 min -1 at a certain temperature. (a) Determine the half-life for the reaction. (b) Determine the time needed for the concentration of SO2Cl2 to decrease to 10% of its initial concentration. (c) If 14.0 g of SO2Cl2 is...

Wilson Yeh 1L

So we have rate=k[A][B] 2 [C] 2 . The initial rate is given in units (mmolA)*L -1 *s -1 . Each of the concentrations are given in units mmol*L -1 . When we multiply all the concentrations of reactants together, we end up with units mmol*L -5 . By dividing (mmolA)*L -1 *s -1 by mmol 5 *L -5 to find ...

Wilson Yeh 1L

So we have rate=k[A][B] 2 [C] 2 . The initial rate is given in units (mmolA)*L -1 *s -1 . Each of the concentrations are given in units mmol*L -1 . When we multiply all the concentrations of reactants together, we end up with units mmol*L -5 . By dividing (mmolA)*L -1 *s -1 by mmol 5 *L -5 to find ...

Wilson Yeh 1L

Determine the value of the rate constant given the following values: A0: 1.25 B0: 1.25 C0: 1.25 Initial Rate: 8.7 Rate law: k[A][B]^2[C]^2 Using the concentrations given in mmol*L^-1 and rates given in mmol A*L^-1*s^-1, I got the value 2.85. However, in the answer the value is 2.85x10^12. Can someon...

Wilson Yeh 1L

How do coefficients relate to the order of a reaction? Like the coefficients in both the product and reactant? And how do the number of products produced relate to the order and rate?

Wilson Yeh 1L

For the final, will we need to know how to derive kinetic equations? Like using calculus to change the form of a given equation? Thanks!

Wilson Yeh 1L

How come rates aren't negative for consumption and positive for formation? I know it's convention to have it as positive but I'm just curious as to the background behind this.

Wilson Yeh 1L

Say my answer is Cl2 + H2O --> Cl- + HClO + H+, could I also write it as H20 + Cl2 --> HClO + Cl- + H+?

Is there a standard way to order this? Or does it not matter? Thanks!

Wilson Yeh 1L

Or is Pt the only one you could use, assuming there's no solid in the cell and you need a solid?

Wilson Yeh 1L

Copper reacts with dilute nitric acid to form copper(II) nitrate and the gas nitric oxide, NO. Write the net ionic equation for the reaction. What would be the equation for this problem be? I set it up as Cu + HNO3 --> Cu(NO3)2 + NO but I'm pretty sure that's wrong. Can someone explain to me what I'...

Wilson Yeh 1L

Write the half reactions and the balanced equation for the cell reaction for each of the following galvanic cells: d.) Pt(s)|O2(g)|H+(aq)||OH-(aq)|O2(g)|Pt(s) e.) Pt(s)|Sn4+(aq),Sn2+(aq)||Cl-(aq)|Hg2Cl2(s)|Hg(l) How would I go about doing d and e? A through c was pretty straightforward in that on th...

Wilson Yeh 1L

A heat pump heats a house in winter by extracting heat from the cold outdoors and releasing it into the warm interior. For the transfer of a given amount of heat, (a) how do the entropies of the interior and exterior of the house change (increase or decrease)? (b) Which change is greater? Assume tha...

Wilson Yeh 1L

For part A: Calculate the standard Gibbs free energies of formation of the halogen atoms X(g) at 1000. K from data available in Table 11.2.

Why is the standard Gibbs free energies of formation in the answer given in positive values and not negative?

Wilson Yeh 1L

The overall photosynthesis reaction is 6 CO2(g) + 6 H2O(l) --> C6H12O6(aq) + 6 O2(g). Standard enthalpy of reaction is +2802 kJ. State the equilibrium composition. The answer states for part B and part F that there is no effect when the system is compressed and water is added, respectively. Why is t...

Wilson Yeh 1L

Why does delta U = 0 for an isothermal expansion of an ideal gas?

Wilson Yeh 1L

In section 8.10, it states Cv,m is 3/2 * R for atoms, 5/2 * R for linear molecules, and 3R for nonlinear molecules. Aren't diatomic molecules like oxygen linear? So what would be the rule there for what value to use? I know it should be 3/2 * R but could someone clarify this for me? Thanks!

Wilson Yeh 1L

Can someone explain to me when to use Cv and when to use Cp? My TA discussed this in my discussion section but I still don't understand when to use either. Yes, I get that you use Cv under constant volume and you use Cp under constant pressure, but I still don't understand when you would use it. The...

Wilson Yeh 1L

Is there a standard unit of pressure for the equation \Delta S = nRln\frac{P1}{P2} Like say they give it in atm, kPA, bar, etc. does it matter if I just use those units straight up or do I have to convert it to a standard unit like atm? From the textbook it doesn't seem like I have to, but I'm reall...

Wilson Yeh 1L

A gaseous mixture consisting of 2.23 mmol N2 and 6.69 mmol H2 in a 500.-mL container was heated to 600. K and allowed to reach equilibrium. Will more ammonia be formed if that equilibrium mixture is then heated to 700. K? For N2(g) + 3 H2(g) <--> 2 NH3(g), K = 1.7 x 10-3 at 600. K and 7.8 x 10-5 at ...

Wilson Yeh 1L

I also got -2.7 kJ/mol! I spent the past hour trying to figure out what I was doing wrong but it seems like it might just be an error in the solution.

Wilson Yeh 1L

Start with the equations \Delta G = \Delta G^{o} + RTlnQ and \Delta G^{o} = -RTlnK Everything is given except Q, which can be calculated using the partial pressures given. The Gibbs free energy of the reaction can then be calculated. Hope this helps! Thanks! I did it but ended up with 8.3 not the a...

Wilson Yeh 1L

(a) Calculate the reaction Gibbs free energy of I2(g) --> 2I(g) at 1200. K (K = 6.8) when the partial pressures of I2 and I are 0.13 bar and 0.98 bar, respectively. (b) What is the spontaneous direction of the reaction? Explain briefly.

Can someone explain how to approach this? I'm so lost.

Wilson Yeh 1L

The volume of real gases are greater and harder to compress. Because of this, entropy of real gases are greater than entropy of ideal gases.

Wilson Yeh 1L

Can somebody give me a detailed reasoning for why each answer is what it is? I feel like I have a general idea but I'd like to be sure. Thanks! 9.27 Which substance in each of the following pairs has the higher molar entropy at 298 K: (a) HBr(g) or HF(g); (b) NH3(g) or Ne(g); (c) I2(s) or I2(l); (d)...

Wilson Yeh 1L

For the equation:
delta(S) from T1 to T2 = n*C*ln(T2/T1)

Where does the C come from? Is that supposed to be heat capacity, and of what exactly? Also, how would I go about solving a problem involving a change in temperature and entropy utilizing this equation if C isn't given? Thanks!

Wilson Yeh 1L

The energy increases. It's also important to note that energy is required to break bonds within a system and energy is lost when bonds are formed.

Wilson Yeh 1L

Usually in questions where say a piece of ice is dropped in water in order to calculate heat flow, energy change, etc. I generally take into account that the ice will melt into water completely and use that energy in order to answer my problem. However, I was wondering how I would know of a situatio...

Wilson Yeh 1L

Determine the reaction enthalpy for the hydrogenation of ethyne to ethane, C2H2(g) + 2 H2(g) --> C2H6(g), from the following data: DeltaHc(C2H2, g) -1300. kJ·mol-1, DeltaHc(C2H6, g) -1560. kJ·mol-1, DeltaH(H2, g) -286 kJ·mol-1. I understand how to do this problem using Hess's Law, the first method. ...

Wilson Yeh 1L

The problem asks later on, "How much heat is absorbed in the reaction of 1.25 mol S8 at constant pressure?" showing that the reaction needs energy in the form of heat. Not all chemical reactions are exothermic; some such as this one are endothermic and require energy to take place. I unde...

Wilson Yeh 1L

In question 8.45 it states that carbon disulfide can be prepared from coke and elemental sulfur:

4C(s)+S8(s) --> 4CS2(l)
delta(H) = +358.8 kJ

My question is I thought that whenever something is being formed it would be exothermic, so in this case why is it positive 358.8 kJ not negative?

Wilson Yeh 1L

I think if the question supplies the specific heat capacity of the container then yes, you would have to account for the specific heat of the container.

Wilson Yeh 1L

The answer is positive because when compressing a bike pump you're doing work and increasing the internal energy inside the pump. Basically, the energy is being transferred from you into the air inside the bike pump. As such, the energy is positive. It would be negative if energy was released in the...

Wilson Yeh 1L

Why is coffee in a thermos bottle considered an isolated system? Why is it not closed? From personal experience the coffee in my thermos bottles would eventually cool down within an hour or so--doesn't that mean energy is being exchanged with the surroundings?

Wilson Yeh 1L

I did what the above posters did as well and got the same answer. I'm just curious as to why the book answer is 1.4 x 10^2 kJ? Shouldn't it be 1.5 if anything?

Wilson Yeh 1L

I know exams and tests must be written in pen, but just double-checking--are pencils okay for homework problems?

Wilson Yeh 1L

So I know that a state property is not dependent on path taken, but rather just final - initial. However, for a non-state property like work and heat, what would be the equation to solve for it?

Wilson Yeh 1L

In today's lecture there was an example on nitrogen dioxide formation. For method 1, how did the first two reactions add up to form the third reaction? 1. N2 (g) + O2 (g) -> 2NO (g) 2. 2NO (g) + O2 (g) -> 2NO (g) 3. N2 (g) + 2O2(g) -> 2NO2 (g) So my question is how did it get from 1 and 2 to 3?

Wilson Yeh 1L

On top of what the others have posted, I think it's also very important to come up with a way to remember that endothermic reactions break bonds and exothermic reactions form bonds. For me, I just imagine in my head the game of pool when the cue ball is used to break at the beginning of the game. Th...

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