Monday

July 6, 2015

July 6, 2015

Total # Posts: 3,040

**Math(Can someone please answer!!)**

ln [2.30E-2] = ln(0.102) - (k s-1)(2360 s) k = 6.31E-4 s -1 I did 2360k = 1n(0.102 * 0.023) 2360k = -6.055 then I divided 2360 by -6.055 but I didnt get 6.31e-4. Where did I mess up???
*March 11, 2012*

**Math(Can someone please answer!!)**

n [1.70E-2] = ln(0.144) - (k s-1)(3609 s) Solve for k. I have a TI30 calculator. Am I suppose to press just the ln button or do I have to press 2nd and then ln??
*March 11, 2012*

**Math**

ln [1.70E-2] = ln(0.144) - (k s-1)(3609 s) Solve for k. I have a TI30 calculator. Am I suppose to press just the ln button or do I have to press 2nd and then ln??
*March 11, 2012*

**Chemistry**

The decomposition of hydrogen peroxide in the presence of potassium iodide is believed to occur by the following mechanism: step 1 slow: H2O2 + I^- = H2O + OI^- step 2 fast: H2O2 + OI^- = H2O + O2 + I^- 1) What is the equation for the overall reaction? Use the smallest ...
*March 11, 2012*

**Chemistry**

The decomposition of hydrogen peroxide in the presence of potassium iodide is believed to occur by the following mechanism: step 1 slow: H2O2 + I^- = H2O + OI^- step 2 fast: H2O2 + OI^- = H2O + O2 + I^- 1) What is the equation for the overall reaction? Use the smallest ...
*March 10, 2012*

**Chemistry**

1/[N2O] = 1/(1.75M) + (1.10E-3M^-1 S^-1)(1852s) [N2O] = 0.383 M I know I posted a similar question but I am having trouble with this one as well. Should I do 1/1.75 first and then add 1.10e-3 and then multiply by 1852? Math(Thank you for your help) - john, Friday, March 9, ...
*March 9, 2012*

**Chemistry(Please help explain)**

The decomposition of hydrogen peroxide in the presence of potassium iodide is believed to occur by the following mechanism: step 1 slow: H2O2 + I^- = H2O + OI^- step 2 fast: H2O2 + OI^- = H2O + O2 + I^- 1) What is the equation for the overall reaction? Use the smallest integer...
*March 9, 2012*

**Chemistry(Urgent, please answer)**

Disregard question. I figured it out!
*March 9, 2012*

**Chemistry(Urgent, please answer)**

If you are given the slope and y intercept how do you find the rate constant of a chemical equation??? Would I multiply the slope and the y intercept???
*March 9, 2012*

**Math(Thank you for your help)**

So first I did multiplication (1.10e-3)(1852) and then divided 1/1.75 and then added and I cant get the answer.
*March 9, 2012*

**Math(Thank you for your help)**

1/[N2O] = 1/(1.75M) + (1.10E-3M^-1 S^-1)(1852s) [N2O] = 0.383 M I know I posted a similar question but I am having trouble with this one as well. Should I do 1/1.75 first and then add 1.10e-3 and then multiply by 1852?
*March 9, 2012*

**Chemistry(Thank you for your help!)**

O ok I didnt know it was that easy!!! Thank you!
*March 9, 2012*

**Chemistry(Thank you for your help!)**

The following info was obtained: [HI], M 0.535 0.268 0.134 6.70E-2 seconds 0 520 781 911 What is the average rate of disappearance of HI from t = 0 s to t = 520 s The answer is 5.13E-4 M s-1 but I do not understand how to get this!!!Could someone please explain!! Thank you!!
*March 9, 2012*

**Math(Please, please help)**

1/[N2O] = 1/(1.75M) + (1.10E-3M^-1 S^-1)(1852s) [N2O] = 0.383 M I know I posted a similar question but I am having trouble with this one as well. Should I do 1/1.75 first and then add 1.10e-3 and then multiply by 1852?
*March 9, 2012*

**Math(Please answer just a quick question!!!!)**

Ok how did you get 5.56e-3???
*March 8, 2012*

**Math(Please answer just a quick question!!!!)**

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 minutes times -0.0237???
*March 8, 2012*

**Math(Please help)**

ok thank you so much!!!
*March 8, 2012*

**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...
*March 8, 2012*

**Math**

yes thats 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.
*March 8, 2012*

**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...
*March 8, 2012*

**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?
*March 8, 2012*

**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
*March 7, 2012*

**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)
*March 7, 2012*

**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?
*March 6, 2012*

**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. ...
*March 6, 2012*

**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. ...
*March 6, 2012*

**Chemistry(Please help)**

Nevermind I know what I did wrong. I had to divide my final answer by 1000 to get kJ.
*March 6, 2012*

**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.
*March 6, 2012*

**Chemistry(Please help)**

I had to make a graph using lnK vs 1/T adn find the slope. The slope was -1.23e4 and now I have to find Ea. Do I divide the slope by R
*March 6, 2012*

**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?
*March 5, 2012*

**Chemistry**

I had to make a graph using lnK vs 1/T adn find the slope. The slope was -1.23e4 and now I have to find Ea. Do I divide the slope by R?
*March 5, 2012*

**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...
*March 5, 2012*

**Chemistry(Please check)**

Oh I see thats 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.
*March 5, 2012*

**Chemistry(Please check)**

Where did the 2mL come from?
*March 5, 2012*

**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...
*March 5, 2012*

**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 ...
*March 5, 2012*

**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?
*March 5, 2012*

**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?
*March 4, 2012*

**Chemistry(Urgent, please check)**

So besides the weird number I got I'm guessing that I set it up correctly.
*March 4, 2012*

**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?
*March 4, 2012*

**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 ...
*March 4, 2012*

**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 ...
*March 4, 2012*

**Chemistry**

so then 4.
*March 3, 2012*

**Chemistry**

To balance the equation would I add a 2 in front of the O2?
*March 3, 2012*

**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...
*March 3, 2012*

**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?
*March 3, 2012*

**Chemistry(Please check)**

Oh wow I didnt even realize that they were both solids, I understand thank you!!
*March 3, 2012*

**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?
*March 3, 2012*

**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...
*March 3, 2012*

**Math**

Disregard question. I figured it out. You take the ln of -2.035 and then multiply by 2.34 to get k2.
*March 3, 2012*

**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!!
*March 3, 2012*

**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.
*March 3, 2012*

**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!!!!
*March 3, 2012*

**Chemistry(Please check)**

ok thank you!!
*March 3, 2012*

**Chemistry(Please check)**

Ok so 0.0000572 = 5.7 X 10-5 M as the concentration ?
*March 3, 2012*

**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?
*March 3, 2012*

**principles of physics**

outside the earth, but within the orbital path of the moons.
*March 2, 2012*

**Chemistry**

So the equation I use is ln k = a + (-ea/rt) correct?
*February 29, 2012*

**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!
*February 29, 2012*

**Chemistry**

He didnt say, he just posted the question like above.
*February 29, 2012*

**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..
*February 29, 2012*

**Chemistry**

I tryed and got .20. Is this correct?
*February 29, 2012*

**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.
*February 29, 2012*

**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?
*February 29, 2012*

**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?
*February 29, 2012*

**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...
*February 28, 2012*

**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...
*February 28, 2012*

**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?
*February 28, 2012*

**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.
*February 28, 2012*

**Chemistry(Please, please help)**

Disregard question.
*February 28, 2012*

**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 ...
*February 28, 2012*

**Chemistry(Urgent, please help)**

Diregard question.
*February 28, 2012*

**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 ...
*February 28, 2012*

**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 ...
*February 28, 2012*

**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??
*February 28, 2012*

**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 ...
*February 28, 2012*

**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.
*February 27, 2012*

**Chemistry(Please help, thank you)**

Sorry I actually got 0.00666 so it would be 6.6e-3 correct?
*February 27, 2012*

**Chemistry(Please help, thank you)**

So the answer would be 6.66e-2 L*min? Is that the correct unit?
*February 27, 2012*

**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
*February 27, 2012*

**Chemistry(Please help, thank you)**

Is L just the unit? Moles would be 3.33e-3M / L ?
*February 27, 2012*

**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 ...
*February 27, 2012*

**Math(Please check)**

So are you saying thats not the answer????
*February 27, 2012*

**Math(Please check)**

I got 0.011666667 so for correct sig figs is that 1.16e-2 or 1.1e-2?
*February 27, 2012*

**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?
*February 27, 2012*

**Math(Please check)**

(0.50M)(3.50mL) = c2(75.00) c2= 2.3e-2 Is this correct?
*February 27, 2012*

**Physics **

How many seconds will elapse between seeing lightning and hearing the thunder if the lightning strikes 2 mi away and hte temperature is 100 degree F?
*February 27, 2012*

**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 ...
*February 27, 2012*

**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?
*February 27, 2012*

**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)
*February 27, 2012*

**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?
*February 26, 2012*

**Chemistry(Please check)**

(0.80M)(5.00mL) = c2 (75.00mL) c2 = 5.33e-2 M Is the correct amount of sig figs?
*February 26, 2012*

**neuroscience**

discuss spatial and temporal summation
*February 26, 2012*

**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?
*February 26, 2012*

**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?
*February 26, 2012*

**Chemistry**

(2.50mL)(0.10M) / 75.00mL = 0.003333 Im not sure how many sig figs to use. Would it 3.33e-3?
*February 26, 2012*

**Chemistry(Please help)**

I have to convert 1 minute 25 seconds into just seconds. Im not sure what to do. Thank you!!
*February 26, 2012*

**Chemistry**

It says that the final volume for every reaction solution is 75mL so is that what I divide by?
*February 26, 2012*

**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...
*February 26, 2012*

**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 ...
*February 26, 2012*