Tuesday
September 23, 2014

Posts by Hannah


Total # Posts: 2,852

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

physics
what is the power of a 6 ohm bulb when 3 of such bulbs ar econnected in a 12 volt parallel circuit?
February 25, 2012

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 ...
February 25, 2012

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.
February 25, 2012

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?
February 25, 2012

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?
February 25, 2012

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...
February 25, 2012

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 ...
February 25, 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 25, 2012

Math
4x+y=-17 -3x+y=4 Please help me solve each system of equation and show your work.
February 25, 2012

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 ...
February 24, 2012

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?
February 24, 2012

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 ...
February 24, 2012

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 ...
February 24, 2012

Chemistry
6.00 minutes 5 minutes 2 seconds 1 minute 32 seconds So 25.5 seconds / 60 = 0.4250. How can this be minutes?
February 24, 2012

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 didnt ...
February 24, 2012

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...
February 23, 2012

Physical Science
Balance this equation: I2+HNO3 = HIO3+NO2+H2O
February 22, 2012

Chemistry(Urgent, please help,thank you)
oh ok I understand thank you so much for all of your help!!!
February 21, 2012

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...
February 21, 2012

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 ...
February 21, 2012

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? ...
February 21, 2012

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?
February 21, 2012

Physics
what is the voltage acros a 60.0 resistor with a current of 3 1/3 a?
February 21, 2012

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 ...
February 20, 2012

Chemistry(Please help)
Disregard question I understand now. I have to solve for mols.
February 20, 2012

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?
February 20, 2012

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 ...
February 20, 2012

Chemistry(Please help,thank you)
Nevermind, I made a mistake im sorry. Disregard the question.
February 20, 2012

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?
February 20, 2012

Chemistry(Please help,thank you)
Is it ok that "i" is negative?
February 20, 2012

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 ...
February 20, 2012

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 ?
February 20, 2012

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 ...
February 20, 2012

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 L-1 s-1 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...
February 20, 2012

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 6.69e-2?
February 20, 2012

Chemistry
Would it be k[XO]^2[O2] because second order is squared?
February 20, 2012

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 L-ls-l 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]...
February 20, 2012

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?
February 20, 2012

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
February 20, 2012

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.
February 20, 2012

Chemistry
Ok and the units I use would be degrees celsius correct?
February 20, 2012

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?
February 20, 2012

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 ...
February 20, 2012

Chemistry
for my answer I get 0.0669. Should I leave it like this or do 6.69e-2?
February 20, 2012

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.
February 20, 2012

Chemistry
Is this correct?
February 20, 2012

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 L-ls-l 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...
February 20, 2012

Chemistry(Please check)
8. The half-life 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...
February 20, 2012

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 10-3 min-l. If we start with [aldehyde] = 0.0500 molar, what will the concentration be 150 minutes later? 1.20e-3(150) = 0.18 0.18(0.0500)=0.009M The ...
February 20, 2012

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.
February 20, 2012

Chemistry(Please check)
Oh ok I did realize that. Now I got 0.0775M
February 19, 2012

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 half-lives? I did 0.620 -> 0.31 ->0.155 0.155M will be the concentration. Is this correct?
February 19, 2012

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...
February 19, 2012

Chemistry(Please help)
Disregard question.
February 19, 2012

Chemistry(Please help)
I subtracted again and got 9.83. So do I set it up like this 453.74= Xether * 463.57
February 19, 2012

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...
February 19, 2012

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 ...
February 19, 2012

Chemistry
ok thank you!!!
February 19, 2012

Chemistry
I had to perform an experiment for the freezing point depression in which we had to determine the freezing 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 ...
February 19, 2012

Chemistry
Bauxite ore contains aluminum oxide Al2O3(s) which is decomposed using electricity to produce aluminum metal and oxygen gas. What mass of aluminum metal can be procuced from 155g of aluminum oxide?
February 19, 2012

Chemistry
thank you!
February 19, 2012

Chemistry
1. Nitric oxide reacts with bromine gas at elevated temperatures according to the equation, 2 NO(g) + Br2(g) = 2 NOBr(g) The experimental rate law is rate = k[NO][Br2]. In a certain reaction mixture the rate of formation of NOBr(g) was found to be 4.50 x 10-4 mol L-l s-l. What...
February 19, 2012

Chemistry(Please check)
Ok, thank you for your help!!
February 19, 2012

Chemistry(Please check)
so then answers 2 and 3 are not correct?
February 19, 2012

Chemistry(Please check)
So wouldn't a catalyst just speed up the rate too and not the rate constant?
February 19, 2012

Chemistry(Please check)
Oh ok I understand, thank you.
February 19, 2012

Chemistry(Please check)
I just thought that if the concentration was doubled there would be more molecular collisions which would increase the rate law. So only the first two are correct then?
February 19, 2012

Chemistry(Please check)
1) The reaction A + B + C = products has a rate law rate = k times A times C squared. Which of the following will result in an increase in the rate constant for the reaction? #1 - increasing the temperature #2 - adding a catalyst #3 - doubling the concentration of reactant C I...
February 19, 2012

Chemistry(Please check)
The units of a rate constant for zero, first, and second order reactions are given in the textbook. If the time units are minutes, what would you expect the units to be for a third order reaction? 1) 1/min^3 2) mol^2/L^2-min 3) L/mol-min^2 4) L^2/mol^2-min 5) L^2/mol^2-min^2 I...
February 19, 2012

Chemistry
so I did 463.57 - 453.74 = 7.600 Then I found moles of ether to be 4.0313. I do not understand the next step to find Xether.
February 19, 2012

Chemistry
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 This question is similar ...
February 19, 2012

Chemistry(Please check)
oh I understand you have to add them. Thank you.
February 19, 2012

Chemistry(Please check)
Sorry I had to post the question using the word times but for some reason this site would not let me post the original equation using the brackets.
February 19, 2012

Chemistry(Please check)
A reaction has a rate law, rate = k times A times B squared. What is the overall order of the reaction. I think that the order is 0. Is this correct?
February 19, 2012

Chemistry(Please help)
Yes im sorry I am sort of confused. So is the total number of moles what they gave me in the problem, 6.243?
February 19, 2012

Chemistry(Please help)
Yes it just says calculate the vp of the solution when aspirin is dissolved in the CHCl3. So then I do not have to calculate the moles/total moles?
February 19, 2012

Chemistry(Please help)
So I would do 0.0346/180.1 for aspirin and 2.04/119.40 for CHCH3?
February 19, 2012

Chemistry(Please help)
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 ...
February 19, 2012

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 ...
February 19, 2012

Chemistry(Please help, thank you!)
Disregard this question. I actually got the answer.
February 19, 2012

Chemistry(Please help, thank you!)
How would I find the molality of NaCl with the following information? initial temperature= 98degrees celsius final temp=100 degrees celsius. Kbp(water)=0.512
February 19, 2012

Chemistry
We had to measure out 5.800g of NaCl and record the exact weight. First I weighed the measuring boat and then I poured in the NaCl so to get the exact weight I subtracted the mass of the measuring boat with NaCl from the mass of just the boat. Is this correct?
February 18, 2012

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