Posts by hannah
Total # Posts: 3,512

Chemistry
So the equation I use is ln k = a + (ea/rt) correct? 
Chemistry
A particular reaction has an activation energy of 51.6kJ/molrxn. 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. 5.94e3 / 1.11e3 = 5.33e2/2.66e2 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 6.66e3 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. 5.94e3 / 1.11e3 = 5.33e2/2.66e2 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: 5.33e2 M / 2.66e2M = 1.03e2 / 1.93e3 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: 5.33e2 M / 2.66e2M = 1.03e2 / 1.93e3 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 610 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 6.6e3 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 6.6e3 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 6.6e3 correct? 
Chemistry(Please help, thank you)
So the answer would be 6.66e2 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 3.33e3 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 3.33e3M / 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 1.16e2 or 1.1e2? 
Math(Please check)
What about (0.50)(1.75) = c2(75.00) c2=1.16e2. Is this correct in terms of correct number of sig figs? 
Math(Please check)
(0.50M)(3.50mL) = c2(75.00) c2= 2.3e2 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 1.16e3 or 1.16? 
Chemistry(Please check)
(0.80M)(5.00mL) = c2 (75.00mL) c2 = 5.33e2 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 3.33e3? 
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... 
Physical Science
Balance this equation: I2+HNO3 = HIO3+NO2+H2O 
Chemistry(Urgent, please help,thank you)
oh ok I understand thank you so much for all of your help!!! 
Chemistry(Urgent, please help,thank you)
After performing a freezing point depression experiment I had to find the molecular weight of glycol. Now I have to answer the question what value did I assume "i" to equal and why did I make this assumption. My teacher told us the value of i to use for this was 1. I... 
Chemistry
I need to calculate the molecular mass of ehtylene glycol based on the freezing point depression. The teacher said that for glycol i=1 and to use the equation m=delta T / Kf X i Kf = 1.86C/m so I did 2.5C / 1.86 X 1 = 1.344 I know that 1.344 can't be the weight for ... 
Chemistry
1) For a freezing point depression experiment we had to create an ice bath and add salt to the ice. I have to answer the question, why was salting the ice necessary in order to complete the experiment and how does this apply to the principles/concepts behind this experiment? ... 
Physics
Suppose your power company charges $1.00 per kWh as its power rate. (a) What is the power in kW for an air conditioner that pulls 5 A on your standard 115 V household circuit? (b) How much does it cost you to run your air conditioner for 12 hours? 
Physics
what is the voltage acros a 60.0 resistor with a current of 3 1/3 a? 
Chemistry(Please help)
so for molality I got 1.344 then I did 1.344 = mols/0.10kg = 0.1344 Im not sure if I did this step right Then I did mm= g/mol 6.200 was the mass of the solute so mm=6.200 / 0.1344 = 46.13. I guess I made a mistake somewhere in my calculations because I thought that the mm of ... 
Chemistry(Please help)
Disregard question I understand now. I have to solve for mols. 
Chemistry(Please help)
the only info that I have is the mass of solute(g) and mass of solvent(kg) for glycol so im confused on what to use for mols? 
Chemistry(Please help)
I need to calculate the molecular mass of ehtylene glycol based on the freezing point depression. The teacher said that for glycol i=1 and to use the equation m=delta T / Kf X i Kf = 1.86C/m so I did 2.5C / 1.86 X 1 = 1.344 I know that 1.344 can't be the weight for ... 
Chemistry(Please help,thank you)
Nevermind, I made a mistake im sorry. Disregard the question. 
Chemistry(Please help,thank you)
Ok and for sucrose I did 4.5C = 1.86C/m X 0.1004 mol X i 4.5 = 0.1867i i =24 Can i be a big number like this? 
Chemistry(Please help,thank you)
Is it ok that "i" is negative? 
Chemistry(Please help,thank you)
I have to find the calculation of Van't Hoff factor "i" for NaCl and sucrose. The directions say to use the equation delta Tf = kf X m X i and to use Kf for water = 1.86C/m So I have the molality of NaCl and sucrose as well as delta Tf so for NaCl I plugged the ... 
Chemistry
For 0.06697mol / 0.1kg = 0.6697 mol/kg does my answer have the correct amount of sig figs? Same for 0.1004mol / 0.1kg = 1.004mol/kg ? 
Chemistry
had to perform an experiment for the freezing point depression in which we had to determine the frezzing points of water as a pure solvent, sodium chloride, sucrose, and ethylene glycol. We had to work with a partner so I completed the experiment for water, NaCl, and the ... 
Chemistry(Thank you for helping)
1) Given this data in a study on how the rate of a reaction was affected by the concentration of the reactants Initial Rate, RUN # (A), M (B), M (C), M mol L1 s1 1 0.200 0.100 0.600 5.00 2 0.200 0.400 0.400 80.0 3 0.600 0.100 0.200 15.0 4 0.200 0.100 0.200 5.00 5 0.200 0.200... 
Chemistry
I am trying to find th e# of moles of NaCl but I am not sure of the units. For my answer I get 0.0669. Should I leave it like this or do 6.69e2? 
Chemistry
Would it be k[XO]^2[O2] because second order is squared? 
Chemistry
For the reaction, 2 XO + O2 = 2 X02, some data obtained from measurement of the initial rate of reaction at varying concentrations are given below. run # [XO] [O2] rate, mol Llsl 1 0.010 0.010 2.5 2 0.010 0.020 5.0 3 0.030 0.020 45.0 The rate law is therefore a. rate = k[XO]... 
Chemistry
For both NaCl and sucrose we had to mix it with 100ml of water so for the mass of solvent (kg) I would do 100mL X 1.00g/mL = 100g and then to get kg I would divide by 1000 so 0.1kg. This would be the answer for sucrose as well. Is this correct? 
Chemistry
so do I use the weight that I got for NaCl and multiply by 1.00g/mol? Or the solvent in this case is water and we used 100mL 
Chemistry
Now I have to calculate the mass of solvent(kg) for both NaCl and Sucrose and I have to assume that the density of water is 1.00g/mol. I am not sure how to figure this out. I think you already answered this for me once but I cant find my original post with the answer. Im sorry. 
Chemistry
Ok and the units I use would be degrees celsius correct? 
Chemistry
ok so my freezing point for NaCl was 2.0 so I can do 2.0(0.5)= 2.5 degrees celsius. My freezing point for DI water was positive 0.5. So delta T would be 2.5? 
Chemistry
I had to perform an experiment for the freezing point depression in which we had to determine the frezzing points of water as a pure solvent, sodium chloride, sucrose, and ethylene glycol. We had to work with a partner so I completed the experiment for water, NaCl, and the ... 
Chemistry
for my answer I get 0.0669. Should I leave it like this or do 6.69e2? 
Chemistry
I am trying to find th e# of moles of NaCl but I am not sure of the units. 3.914g NaCl / mm=58.44 so is it 3.914g/mol divided by 58.44g/mol = 0.0669moles. I am not sure how many significant figues to use. 
Chemistry
Is this correct? 
Chemistry
For the reaction, 2 XO + O2 = 2 X02, some data obtained from measurement of the initial rate of reaction at varying concentrations are given below. run # [XO] [O2] rate, mol Llsl 1 0.010 0.010 2.5 2 0.010 0.020 5.0 3 0.030 0.020 45.0 The rate law is therefore a. rate = k[XO... 
Chemistry(Please check)
8. The halflife of a reaction was found to be inversely dependent on the concentration of the starting material. Thus, we can say that a. the reaction is zero order b.the reaction is first order c.the reaction is second order d. the reaction starts out first order and changes... 
Chemistry(Please check)
The decomposition of an aldehyde solution in carbon tetrachloride is a first order reaction with a rate constant of 1.20 x 103 minl. If we start with [aldehyde] = 0.0500 molar, what will the concentration be 150 minutes later? 1.20e3(150) = 0.18 0.18(0.0500)=0.009M The ... 
Chemistry
1)For the reaction, A = B + C, the rate law is k(A). If it takes 80.0 seconds for 70.0% of a 10.0 gram sample of A to be transformed into products, what is the value of the rate constant? I was going to do 80/10 = 8 and then 8 times .70 but im not sure this is correct. 
Chemistry(Please check)
Oh ok I did realize that. Now I got 0.0775M 
Chemistry(Please check)
The initial concentration of a reactant in a first order reaction is 0.620 molar. What will be its concentration after 3 halflives? I did 0.620 > 0.31 >0.155 0.155M will be the concentration. Is this correct? 
Chemistry(Please help)
The common laboratory solvent diethyl ether (ether) is often used to purify substances dissolved in it. The vapor pressure of diethyl ether , CH3CH2OCH2CH3, is 463.57 mm Hg at 25oC. In a laboratory experiment, students synthesized a new compound and found that when 27.18 grams... 
Chemistry(Please help)
Disregard question. 
Chemistry(Please help)
I subtracted again and got 9.83. So do I set it up like this 453.74= Xether * 463.57 
Chemistry(Please help)
The vapor pressure of diethyl ether is 463.57 mm Hg at 25 degrees celsius. How many grams of aspirin C9H8O4, a non volatile nonelectrolyte (mw=180.1g/mol), must be added to 216.7g of ether to reduce the vapor pressure to 453.74 mm Hg. Ether=74.12g/mol so I did 463.57  453.74... 
Chemistry
The vapor pressure of chloroform is 173.11 mm Hg at 25 degrees celsius. A nonvolatile, nonelectrolyte that dissolves in chloroform is aspirin. Calculate the vapor pressure of the solution at 25 degrees celsius when 6.243g of aspirin (180.1g/mol) are dissolved in 244.5g of ...