# Posts by Hannah

Total # Posts: 3,342

Math(Please help)
ln [5.01E-3] = ln(4.86E-2) - (1.80E-2s-1)(t s) Solve for t. t = 126 s First I did 4.86e-2 - 1.80e-2 and then on my calculator I pressed the 2nd button and then ln and got 1.031. Then I did the same thing to get the ln of 5.01e-3 and divided that by 1.031 but did not get 126 as...

Math
yes that's what it means and how I posted it is exactly how it is written on my homework but I just cant seem to get that answer.

Math
ln [5.01E-3] = ln(4.86E-2) - (1.80E-2s-1)(t s) Solve for t. t = 126 s First I did 4.86e-2 - 1.80e-2 and then on my calculator I pressed the 2nd button and then ln and got 1.031. Then I did the same thing to get the ln of 5.01e-3 and divided that by 1.031 but did not get 126 as...

Math
If the time elapsed is 4.26 min, what is the value of the rate constant, k? ln[R]t / [R]o = -0.0237 I am not sure how to slove this. Would I do ln 4.26 min X -0.0237?

Chemistry(Please, please help)
If the time elapsed is 4.26 min, what is the value of the rate constant, k? ln[R]t / [R]o = -0.0237 I am not sure how to slove this. Is Rt 4.26 min

Chemistry (stoichiometry)
18.5 grams of calcium chloride reacts with 25.7 grams of sodium phosphate and produces calcium phosphate and sodium chloride. What is the limiting reactant? (show work)

Chemistry(Please help, thank you!)
If the time elapsed is 4.26 min, what is the value of the rate constant, k? ln[R]t / [R]o = -0.0237 I am not sure how to slove this. Is Rt 4.26 min?

Chemistry
I need to calculate the valueof Kc for 5 test tubes for an experiment that I completed on determination of Kc. The equation used was Fe^3+ + SCN^-= FeSCN^2+ After creating an ice table for the first test tube my values for Fe and SCN were 6.5e-4M and for FeSCN I got 5.7e-5M. ...

Chemistry(Please check)
I need to calculate the valueof Kc for 5 test tubes for an experiment that I completed on determination of Kc. The equation used was Fe^3+ + SCN^-= FeSCN^2+ After creating an ice table for the first test tube my values for Fe and SCN were 6.5e-4M and for FeSCN I got 5.7e-5M. ...

Chemistry(Please help)
Nevermind I know what I did wrong. I had to divide my final answer by 1000 to get kJ.

Chemistry(Please help)
I did -1.23e4 / 8.314 = -1479.43 and I tryed 1.23e4 / 8.314 = 1479.43 but my online homework keeps saying that its incorrect.

Chemistry(Please help)
I had to make a graph using lnK vs 1/T and find the slope. The slope was -1.23e4 and now I have to find Ea. Do I divide the slope by R

Chemistry
If the time elapsed is 4.26 min, what is the value of the rate constant, k? ln[R]t / [R]o = -0.0237 I am not sure how to slove this. Is Rt 4.26 min?

Chemistry
I had to make a graph using lnK vs 1/T and find the slope. The slope was -1.23e4 and now I have to find Ea. Do I divide the slope by R?

Chemistry(Please check)
Right so for Fe I did (0.005M) (1.0mL Fe) / (7.0mL total of solutions in the tube) = 7.1e-4. So then my ICE table would say 7.10e-4 for both Fe and SCN because SCN for tube 1 had the same amounts and then I would subtract 7.1e-4 by the concentration of product which was 5.7e-5...

Chemistry(Please check)
Oh I see that's the total of SCN and Fe but we also used 0.1M HNO3 so for the first test time we used 5mL of HNO3 with the Fe, SCN so the total would be 7mL. Fe= (0.005M) (1.0mL) = x(7mL) = 0.000714 So 7.1 e-4 Correct. The teacher said to put the answer in 2 sig figs.

Chemistry(Please check)
Where did the 2mL come from?

Chemistry(Please check)
I think I know where I made a mistake. For the initial concentrations of reactants Fe and SCN it says that I can use the table that was provided to determine how much the total volume of each solution was used. The table that was provided provided the amount of Fe and SCN used...

Chemistry(Please check)
I completed a lab to find the determination of Kc. I have to find the concentrations of reactants at equilibrium using an ICE table. The equation that were are using is Fe^3+(aq) + SCN^-(aq) -> Fe(SCN)^2+(aq) I have to create 5 ICE tables because we used 5 different test ...

Calculus
Find the orthoganal trajectories of the family. Use a graphing utility to graph several members of each family. y = Ce^x What am I supposed to do here? Can someone point me in the right direction?

Chemistry
If the charge to mass ratio of a proton is 9.58 x 10^7 coulomb/kilogram and the charge is 1.60 x10^-19 coulomb, what is the mass of the proton?

Chemistry(Urgent, please check)
So besides the weird number I got I'm guessing that I set it up correctly.

Chemistry(Urgent, please check)
I put it in my calculator as 1.0 - 5.7 X e-5 and got 0.999943 I don't know why?

Chemistry(Urgent, please check)
I completed a lab to find the determination of Kc. I have to find the concentrations of reactants at equilibrium using an ICE table. The equation that were are using is Fe^3+(aq) + SCN^-(aq) -> Fe(SCN)^2+(aq) I have to create 5 ICE tables because we used 5 different test ...

Chemistry(Please check, thank you!)
I completed a lab to find the determination of Kc. I have to find the concentrations of reactants at equilibrium using an ICE table. The equation that were are using is Fe^3+(aq) + SCN^-(aq) -> Fe(SCN)^2+(aq) I have to create 5 ICE tables because we used 5 different test ...

Chemistry
so then 4.

Chemistry
To balance the equation would I add a 2 in front of the O2?

Chemistry
For the reaction system, 2 H2O(g) + O2(g) == 2 H2O2 (g), the equilibrium concentrations are (H2O2) = 0.120 M; (H2O) = 0.860 M; (O2) = 0.330 M. Calculate the value of Kc for this reaction. A. 0.423 B. 0.872 C. 0.0590 D. 1.31 E. 2.51 I did 0.120 / 0.860 X 0.330 = 4.4228 = 4.23...

Chemistry
The reaction, 2 SO3(g) == 2 SO2(g) + O2(g) is endothermic. Predict what will happen if the temperature is increased. A. the pressure decreases B. more SO3(g) is produced C. Kc increases D. Kc decreases E. none of the above I chose that Kc will increase. Would you agree?

Chemistry(Please check)
Oh wow I didn't even realize that they were both solids, I understand thank you!!

Chemistry(Please check)
The equilibrium constant, Kc for the system, CaO(s) + CO2(g) == CaCO3(s), is A. Kc = (CaO) (CO2) / (CaCO3) B. Kc = (CO2) C. Kc = (CaCO3)/(CaO) D. Kc = (CaCO3) / (CaO) (CO2) E. Kc = 1 / (CO2) My answer is (CaCo3) / (CaO)(CO2). Would you agree?

Chemistry(Please check)
For the reaction, 2 SO2(g) + O2(g) == 2 SO3(g), at 450.0 K (Kelvin) the equilibrium constant, Kc, has a value of 4.62. A system was charged to give these initial concentrations, (SO3) = 0.254 M and (O2) = 0.00855 M, and (SO2) = 0.500 M. In which direction will it go? A. to the...

Math
Disregard question. I figured it out. You take the ln of -2.035 and then multiply by 2.34 to get k2.

Math
ln k2/2.34 = -103,000J/8.314J/Kol[1/339K - 1/359K] ln k2/2.34 = -2.035941063 I am not sure what to do now!!

Chemistry(Please check answer)
For my online homework when I put the answer in it keeps saying its wrong and says k[reactant 1]^order1 [reactant 2]^order2 but I thought I did this.

Chemistry(Please check answer)
2NO(g) + Br2(g) -> 2NOBr(g) What is the rate equation? My answer is k[NO]2[Br2] Is this correct? Thank you!!!!

Chemistry(Please check)
ok thank you!!

Chemistry(Please check)
Ok so 0.0000572 = 5.7 X 10-5 M as the concentration ?

Chemistry(Please check)
I ahve to find the concentration of product, (Fe(SCN)^2+) at equilibrium. We have to use the equation k=A/C I have the value for k and A so my equation is 7917.6 = 0.453/C = 3586.67M Did I do the math correctly?

principles of physics
outside the earth, but within the orbital path of the moons.

Oceanography
I need that broken down cause I'm 11 and I have no idea what I am doing. Help!

Chemistry
So the equation I use is ln k = a + (-ea/rt) correct?

Chemistry
A particular reaction has an activation energy of 51.6kJ/mol-rxn. How much faster is the reaction at 50 degrees C versus 25degrees C? I do not know how to start this!

Chemistry
He didn't say, he just posted the question like above.

Chemistry
Those were the values that the teacher put in there. I just assumed that since H2 and Br2 are -x and HBr is +2x that HBr would be 2 X 0.10..

Chemistry
I tryed and got .20. Is this correct?

Chemistry
For H2(g) + Br2(g) -> 2HBr(g) k=64 <- Ice table: H2 Br2 HBr I 0.10 0.10 0 C -x -x +2x E Solve for HBr at equilibrium I do not know how to start this.

Chemistry(Urgent, please check!!!)
The equation A + 2 B = C + D describes an elementary reaction, which takes place in a single step. Thus, the rate law must be? My answer is k(A)(B)^2 Is this correct?

Chemistry(Please check)
If the reaction Cl2 (g) + O3 (g) = Cl2O (g) + O2 (g) occurred in just two steps, what would be the overall order of the reaction be? a. 1 b. 2 c. 3 d. 4 e. not possible to determine from the information given I chose 2 as the answer. Is this correct?

Chemistry
I posted a question like this but my numbers were actually wrong. These are the correct ones. 5.94e-3 / 1.11e-3 = 5.33e-2/2.66e-2 5.35 = 2.00^m I guess this is not correct because I do not know a whole number that will give you 5.35. Chemistry - DrBob222, Tuesday, February 28...

Chemistry
Im pretty sure the concentrations that I obtained for the 5 flasks used are correct im just not sure I calculated the rate for each correctly. I was suppose to use the number of moles of I2 produced/L*min. For my I2 I got 6.66e-3 which was half of the S2O3^2- value which was 3...

Chemistry
It says to round the calculated p,q or z values to the nearest integer so that would be 5. Do you think that my numbers for M or rate are just incorrect?

Chemistry
I posted a question like this but my numbers were actually wrong. These are the correct ones. 5.94e-3 / 1.11e-3 = 5.33e-2/2.66e-2 5.35 = 2.00^m I guess this is not correct because I do not know a whole number that will give you 5.35.

Chemistry(Please, please help)
Disregard question.

Chemistry(Please, please help)
I need to find the order of a reaction with respect to the reactants. I set up my equation like this: 5.33e-2 M / 2.66e-2M = 1.03e-2 / 1.93e-3 I did the concentrations equal to the rates. I am just not sure what the units for rate should be. 2.00 = 5.33^m Did I set this up ...

Chemistry(Urgent, please help)
Diregard question.

Chemistry(Urgent, please help)
I need to find the order of a reaction with respect to the reactants. I set up my equation like this: 5.33e-2 M / 2.66e-2M = 1.03e-2 / 1.93e-3 I did the concentrations equal to the rates. I am just not sure what the units for rate should be. 2.00 = 5.33^m Did I set this up ...

Chemistry(Please check, thank you!!)
For my rate of reaction experiment I have to answer the question "why did we ask you to measure the room termperature and temperature of reaction solutions". For the experiment we used 5 flasks and we put one of them in an ice bath at 6-10 degrees C. My answer is ...

Math
1 mintue 25 seconds converted into seconds. I know there are 60 minutes in an hour and seconds 60 in a minute. Am I just dividing by 60??

Chemistry(please help)
I have to calculate the concentration of I2 produced (# of moles of I2 produced / L) based on the stoichiometric ratio in the following equation. 2S2O3^2- + I2 -> 2I^- + S4O6^2- So I got 6.6e-3 L*min for the amount of I2 produced. Now I have to calculate the rate for each ...

Chemistry(Please help, thank you)
So I got 6.6e-3 L*min for the amount of I2 produced. Now I have to calculate the rate for each of the 5 flasks used, so is the answer going to be the same for all 5?? It says to calculate the rate of reaction for each run using # of moles of I2 produced/L*min as the unit.

Chemistry(Please help, thank you)
Sorry I actually got 0.00666 so it would be 6.6e-3 correct?

Chemistry(Please help, thank you)
So the answer would be 6.66e-2 L*min? Is that the correct unit?

Chemistry(Please help, thank you)
So to find the amount of I2 produced as I first posted, it would be 1/2 that of 3.33e-3 correct? So 0.0666? Sorry, its important that I understand this correct

Chemistry(Please help, thank you)
Is L just the unit? Moles would be 3.33e-3M / L ?

Chemistry(Please help, thank you)
I have to calculate the concentration of I2 produced (# of moles of I2 produced / L) based on the stoichiometric ratio in the following equation. 2S2O3^2- + I2 -> 2I^- + S4O6^2- Chemistry(Urgent, please help) - DrBob222, Sunday, February 26, 2012 at 9:47pm If you know the ...

Math(Please check)
So are you saying that's not the answer????

Math(Please check)
I got 0.011666667 so for correct sig figs is that 1.16e-2 or 1.1e-2?

Math(Please check)
What about (0.50)(1.75) = c2(75.00) c2=1.16e-2. Is this correct in terms of correct number of sig figs?

Math(Please check)
(0.50M)(3.50mL) = c2(75.00) c2= 2.3e-2 Is this correct?

Physics
How many seconds will elapse between seeing lightning and hearing the thunder if the lightning strikes 2 mi away and the temperature is 100 degree F?

Physics
A ball is dropped from 27.0 ft above the ground. (a) Using energy considerations only, what is the velocity of the ball just prior to it hitting the ground? (b) If the ball is thrown back up to a ledge 15 m above the ground, what would be the velocity just as it reaches the ...

AB Calculus
So I'm supposed to verify the solution of the differential equation. The solution is y=e^(-x). The differential equation is 3y' + 4y = e^(-x). What is the problem asking me to do here?

algebra
f(x) = .70x You are taking 30% off, and 100%-30% is 70%. So you just multiply x (which is the original price marked on the item) by .70. So the shoes would be 65(.70) the slacks would be 48(.70) and the belt would be 15.50(.70)

Chemistry(Please check)
Ok so the answer is just 5.33? For an equation like this (0.50M)(1.75mL)= C2(75.00mL) would the answer just be 1.16e-3 or 1.16?

Chemistry(Please check)
(0.80M)(5.00mL) = c2 (75.00mL) c2 = 5.33e-2 M Is the correct amount of sig figs?

neuroscience
discuss spatial and temporal summation

Chemistry(Urgent, please help)
All I have is the concentration of S2O3^-2 which is 3.33e^-3M. How would I find moles? For the experiment we used 2.50mL of Na2S2O3. Do I use this to find moles?

Chemistry(Urgent, please help)
I have to calculate the concentration of I2 produced (# of moles of I2 produced / L) based on the stoichiometric ratio in the following equation. 2S2O3^2- + I2 -> 2I^- + S4O6^2- Would the # produced be 2 for I2. I am not sure what to use for L?

Chemistry
(2.50mL)(0.10M) / 75.00mL = 0.003333 Im not sure how many sig figs to use. Would it 3.33e-3?

Chemistry(Please help)
I have to convert 1 minute 25 seconds into just seconds. Im not sure what to do. Thank you!!

Chemistry
It says that the final volume for every reaction solution is 75mL so is that what I divide by?

Chemistry
I had to perform an experiment for rate of reaction. The point of the experiment was to show how changes in reactant concentration, temperature, and catalyst presence can affect the rate of a reaction. The reaction that we studied was H2O2 + 2I^- + 2H^+ -> I2 + 2H2O We had...

Chemistry(Please check answers)
1) The decomposition of hydrogen peroxide in solution and in the presence of iodide ion was studied in laboratory, and the following mechanism proposed based on the experimental data. H2O2 + I - = H2O + IO - (slow) H2O2 + IO - = H2O + O2 + I - (fast) Which one of the ...

physics
what is the power of a 6 ohm bulb when 3 of such bulbs ar econnected in a 12 volt parallel circuit?

Chemistry(Please check)
1) The decomposition of hydrogen peroxide in solution and in the presence of iodide ion was studied in laboratory, and the following mechanism proposed based on the experimental data. H2O2 + I - = H2O + IO - (slow) H2O2 + IO - = H2O + O2 + I - (fast) Which one of the ...

Physics
What is the actual formula you are using? I cannot tell what you mean when you say "v=331.4 +0.6t". I want to actually learn how to do it.

Physics
how many seconds will elapse between seeing lightning and hearing the thunder if the lightning strikes miles away and the temperature is 100.0 degrees F?

Physics
A ball is dropped from 27.0 feet above the ground. Using energy considerations only, what is the velocity of the ball prior to it hitting the ground? If the ball is thrown back up to a ledge 15m above the groud, what would be the velocity as it reaches the ledge?

Chemistry(Please check)
1) The decomposition of hydrogen peroxide in solution and in the presence of iodide ion was studied in laboratory, and the following mechanism proposed based on the experimental data. H2O2 + I - = H2O + IO - (slow) H2O2 + IO - = H2O + O2 + I - (fast) Which one of the following...

Chemistry
Yes I think that helps me. Im not very good at this stuff so let me make sure I understand this. The concentration of the thiosulfate used was 0.10M and for each flask we used 2.50mL. So I have to multiply these two (2.50mL)(0.10M) and then divide by the total amount combined ...

Chemistry
I had to perform an experiment for rate of reaction. The point of the experiment was to show how changes in reactant concentration, temperature, and catalyst presence can affect the rate of a reaction. The reaction that we studied was H2O2 + 2I^- + 2H^+ -> I2 + 2H2O We had ...

Math
4x+y=-17 -3x+y=4 Please help me solve each system of equation and show your work.

Chemistry(Please check)
1) A catalyst alters the rate of a reaction by a. changing the products in the reaction. b. increasing the activation for the reaction. c. always providing a surface on which the molecules react. d. providing an alternate pathway for the reaction. e. increasing the ...

Chemistry(Please check)
1) The reaction: A + 3B = D + F was studied and the following mechanism was finally determined A+B=C (fast) C+B=D+E (slow) E+B=F (very fast) Which step has the largest activation energy? I chose the second step because it is slow and should have the most energy. Is this correct?

Chemistry
Im sorry. The point of the experiment was to show how changes in reactant concentration, temperature, and catalyst presence can affect the rate of a reaction. The reaction that we studied was H2O2 + 2I^- + 2H^+ -> I2 + 2H2O We had to set up 6 flasks each with and certain ...

Chemistry
I had to perform an experiment for rate of reaction. I have to calculate the concentration of Na2S2O3 in the reaction solutions based on the volume used in each reaction flask and the total volume calculated. There were five flasks used and for all 5 of them 2.50mL of Na2S2O3 ...

Chemistry
6.00 minutes 5 minutes 2 seconds 1 minute 32 seconds So 25.5 seconds / 60 = 0.4250. How can this be minutes?

Chemistry
I need to convert these 5 values of time into minutes. 1)1.07 1min 7 seconds 2) 6.00 3) 5.02 4) 1.32 5) 25.5 seconds The example that was given for conversion was 5 min 40 sec = 5.67min These are the values that I got after dividing by 60. 1) 1.07 = 1.12min 2) 6.00 = I didn&#...

ChemHelp
Chem Help! Limiting and excess reagent? Identify the limiting and excess reagent for each of the following scenarios involving the formation of silicone dioxide, SiO2. Please explain!!! Thank you! Si + O2 --> SiO2 a. 2 atoms of silicone and 2 molecules of oxygen gas b. 28.1...

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