Monday
November 24, 2014

Posts by donna


Total # Posts: 438

Chemistry, Arrhenius law
The rate constant of a first order reaction is 4.60x10^-4/s at 350 degrees Celsius. If the activation energy is 104 kJ/mol, calculate the temp. at which its rate constant is 8.80 x 10^-4/s. So I think that I can use this version of the equation: ln (k1/k2) = Ea/R * (T1-T2/T1*...
May 28, 2008

Chemistry
The burning of methane in oxygen is a highly exothermic reaction. Yet a mixture of methane and oxygen gas can be kept indefinitely without any apparent change. Can someone give me an explanation behind this?
May 27, 2008

Chemistry
Write rate law expressions? 2NOCl(g) --> 2NO(g) + Cl2(g) S2O3^2-(aq) + H^+(aq) --> HSO3^-(aq) + S(s) (Sulfur initially forms a colloid solution so it can be treated as aqueous.) (1) Write the rate law expression for the above reactions, assuming these are elementary. (2...
May 21, 2008

Math
Nope, there was no typo, and the answer was 0. Thanks for the clarification!
May 19, 2008

Math
Find y'(x) when cos y - y^2 = 8 a) -siny - 2y b) - (1/sin y - 2y) c) 0 d) - (8/cos y - y) So if I implicitly differentiate: y'(x) = -sin(y) - 2y y' = 0 Am I right to say that there's nothing more you can do to this and pick C? y' = 0 / (-siny - 2y) So y'...
May 19, 2008

Math
1. Find y'(x) when xsecy - 3y sinx = 1 a) (3ycosx - sec y) / (xsec^2y - 3sinx) b) (3cosx - sec x) / (xsecytany - 3sinx) c) (3ycosx - sec y) / (xsecytany - 3sinx) d) (3ycosx - secytany) / xsec^2y - 3sinx) This is what I did: xsecy - 3y sinx = 1 => sec y + x sec y tan y...
May 19, 2008

chemistry
Which solution would increase the osmotic pressure of water the most? a) KBr b) NaCl c) MgCl2 d) glucose
May 19, 2008

chemistry
H-bonding is an intermolecular force that happens with electronegative atoms and H, namely nitrogen, fluorine, and oxygen. H-F H-N H-O
May 16, 2008

Electrochemistry
Qualitively explain the effect of changing concentration of Cu^2+ using your experimental observations and the Keq values below (no calculations required) Cu^2+(aq) + 4 NH3(aq) --> [Cu(NH3)4]^2+(aq) , Keq = 1.2x10^12 CuS(s) --> Cu^2+(aq) + S^2-(aq) , Keq = 8.5 x 10^-45 ...
May 16, 2008

Electrochemistry
Thanks for replying! Cu/Al For example, for the cell combination of Cu/Zn I got a voltage potential of 0.515V. So is this the cell potential? You didn't show your work here so I can't check it for cell potential. ^ I didn't do any work, that was the reading that ...
May 16, 2008

Electrochemistry
In lab, we did an experiment with electrochemical cells with solutions of ZnSO4, CuSO4, Al2(SO4)3 and MgSO4 and their respective metal electrodes. There are a couple of post-lab questions that I'm not sure about: (1) Summarize Part A with a data table containing the ...
May 16, 2008

Chemistry
Oh, sorry, I meant Sr3(PO4)2. That's what I wrote down but I didn't type it properly.
May 14, 2008

Chemistry
For a reaction between sodium phosphate and strontium nitrate write out the following: a) The balanced molecular equation b) The ionic equation c) The net ionic equation a) I think I have this one: 2 Na3PO4 (aq) + 3 Sr(NO3)2 (aq) --> 6 NaNO3 (aq) + Sr(PO4)2 (s) b) Should I ...
May 14, 2008

Chemistry
You are carrying out the titration of 100.0 mL of 1.000M acetic acid with 1.000 M sodium hydroxide. Ka = 1.76x10^-5 of acetic acid. (a) Calculate the initial pH of your acetic acid sample. (b) Calculate the pH of the solution after the addition of 25.0mL of NaOH. For (a) ...
May 13, 2008

mathematics
If 3xy^3 - 4x = 10y^2, find y ' (x) a) (4 + 3y^2)/(9xy^2 + 20y) b) (4 - 3y^2)/(9xy^2 - 20y) c) (3 + 4y^2)/(20xy^2 + 9y) d) (3 - 4y^2)/(20xy^2 - 9y)
May 11, 2008

physics!!!!!
A small spherical insulator of mass 8.00*10^-2kg and charge +6.00*10^-7C is hung by a thin wire of negligible mass. A charge of -9.00*10^-7C is held 0.450m away from the sphere and directly to the right of it, so the wire makes an angle with the vertical. Find (a) the angle ...
March 23, 2008

physics!!!
A small spherical insulator of mass 8.00*10^-2kg and charge +6.00*10^-7C is hung by a thin wire of negligible mass. A charge of -9.00*10^-7C is held 0.450m away from the sphere and directly to the right of it, so the wire makes an angle with the vertical. Find (a) the angle ...
March 22, 2008

Beginning Chemistry
My granddaughter needs help with a worksheet. Use the factor-label method and include all work. Calculate the mass of 500.0cmx3 of the element gold.
March 11, 2008

AP US History
What was the name of the brillantly colored woven cotten cloth produced br the asante tribe wirn by african americans as declaration of their heritage?
January 31, 2008

SCI
I am a mom that works full-time with six kids. I am looking for help when I go to homework sites. You guys are idiots just because someone asks for help does not mean that they are cheating they just might need help. So if you are not going to help SCREW YOU !!!!!!! and if ...
January 13, 2008

biology
what object is like a cell
January 2, 2008

art
Marcel Duchamp.
December 12, 2007

physics
1. how much work do you do on a 25-kg backpack when you walk a horizontal distance of 100 m? -I got 2,500 J 4. if you friend pushes a lawnmower four times as far as you do while exerting only half the force, which one of you does more work? how much more? ( I dont understand ...
October 17, 2007

Physics
Can you please help me with the following questions? please. 1. how much work do you do on a 25-kg backpack when you walk a horizontal distance of 100 m? -I got 2,500 J 4. if you friend pushes a lawnmower four times as far as you do while exerting only half the force, which ...
October 16, 2007

business math
Consider a system of notebook computers for a college math laboratory. The set of computers costs $10,000 and will be salvaged for $2,000 at the end of a 3-year period. Prepare a depreciation schedule using a 150%-declining balance rate for the system. The depreciation ...
June 20, 2007

Business Math
Consider a system of notebook computers for a college math laboratory. The set of computers costs $10,000 and will be salvaged for $2,000 at the end of a 3-year period. Prepare a depreciation schedule using a 150%-declining balance rate for the system. The depreciation ...
June 20, 2007

language
I need to write a paragraph describing my utopian community. What is your ideal community? If you post your paragraph, we'll be glad to comment on it. Thank you for using the Jiskha Homework Help Forum. You only have to write ONE paragraph? Here's how to do that: Here...
May 20, 2007

chemistry
Can someone please help me with this problem? An iron nail placed in a beaker with a solution of silver nitrate will cause pure silver to collect on the bottom of the beaker. Write a balanced equation for the reaction that occurs. This is what I have so far: Fe + AgNO3 --->...
February 28, 2007

Could someone help me proofread?
I think you should know that eggshell and teeth consist of quiet different chemical actually, eggshell is 94-97% Calcium carbonate while teeth is 98% Calcium Phosphate..Calcium phosphate (hydroxyapatite) react with fluoride and formed Fluoroapatite, which is stronger to acid ...
December 28, 2006

Finance
847.86
December 11, 2006

Math Word Problem
Todd has indigo, yellow, pink, and red flowers in his green house. The ratio of indigo flowers to yellow is 3 to 5. The ratio of yellow to pink is 2 to 4. The ratio of indigo flowers to red is 2 to 5. There are 6 indigo flowers. How many flowers of each color is Todd growing? ...
December 4, 2006

Math
The kingston parks and recreation dept. is planning a new that will be 100 yards long and 85 yards wide. The dept. recommended that the trees be planted along the perimeter of the park at equal distances from each other and as far apart as possible. How far apart can the trees...
December 4, 2006

math
when you say subtraction you minuis yes I think it's "minus"
October 27, 2006

math
what is 100.00 +1.002.00 Please check your problem. 1.002.00 is not a standard way of writing a number. We don't use two periods in a number. 1002.00 1002.00 + 100.00 = 1102.00
October 27, 2006

Analogies (just one)-- please help
place is to set as yield is to: protect obstinate retention capitulate
September 14, 2006

brain teaser help
50 states in the Union is 50 S in U I think
August 20, 2005

Science
Which trophic levels have the most biomass? Which have the most energy? Why? The second law of thermodynamics requires that the primary producers have the most biomass and total energy. See:http://www.physicalgeography.net/fundamentals/9o.html
August 1, 2005

unscrambling word
please help me to unscramble this saying! dare to believe. here are the letters chitogoarntoasurwayht the first word has 5 letters second has 4 third has 5 fourth has 2 fifth has 1 sixth word has 4. please help. please help me to unscramble this saying! dare to believe. here ...
June 14, 2005

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