Total # Posts: 633
How can island biogeography be compared to the design of nature reserves? I understandall the things you can do to the nature reserve in terms of bettering it but how is an island similar to a wildlife refugee or reserve (why can you compare them)? can someone please explain?
September 2, 2009
Which would react faster with MeI in aqueous solution: OH- or Et3N? I know that the reaction in aqueous solution would be an Sn1 reaction and so steric hindrance wouldn't have such a great effect. I am not sure which is a better nucleophile out of OH- and Et3N. OH- is ...
May 26, 2009
A set of homogeneous simultaneous equations is given by x + ky = 0 kx + 3y = 0 Calculate the two values of k that lead to non-trivial solutions to these equations and express y in terms of x for the two values. I thought that for the solutions to be no trivial the determinant ...
May 17, 2009
I am attempting to answer a question which asks to explain the sequence of pKaH values for a series of substituted guanidines (NH2)2CNR where R varies. The order is R = H , Ph , CH3CO , MeO , CN , NO2 pKaH = 14.5 , 10.8 , 8.3 , 7.5 , -0.4 , -0.9 I'm not quite sure how to ...
May 4, 2009
Why does CdCO3 have a significantly lower decomposition temperature than CaCO3, despite the similarity in the ionic radii of Ca2+ and Cd2+? I think they both decompose to give the metal oxide and carbon dioxide. Could the polarising ability of Ca compared with Cd have ...
April 23, 2009
louis drew all of the possible diagonals from one vertex of a regular hexagon. Which of these statements is true? A) Each diagonal from this vertex is one of two different lengths B) None of the diagonals forms a line of symmetry of the hexagon. C) The diagonals form four ...
April 22, 2009
a parallel RLC bandpass circuit with C=10nF and Q=10 has a center frequency of 500 krad/s. Find R,L and the two cutoff frequencies. Can you design this circuit using a cascade connection of two first-order filters seperated by a follower?
April 20, 2009
For the transfer function Tv(s)=[10(s+5)(s+20)]/[(s+1)(s+100)] is this a low-pass, high-pass, bandpass or bandstop function? estimate the corner frequency(ies) estimate the passband gain what is the output if v1(t)=10cos(1000t+45deg) V??
April 20, 2009
Why is the carbonyl group in tert-butoxycarbonyl group (tBOC) less susceptible to attack from nucleophiles than the carbonyl group in esters such as ethyl acetate? Is this something to do with conjugation?
April 13, 2009
Is this the correct equation for the formation of [Co(NH3)5(ONO)]^2+ from [Co(NH3)5Cl]^2+ ... [Co(NH3)5Cl]^2+ + NO2 --> [Co(NH3)5(ONO)]^2+ + Cl- I'm a bit unsure because the charges don't balance
April 8, 2009
You are having a pool party and invite 2 of your best friends. These two friends each invite two other people. Each of these 2 people invite 2 people that haven't been invited. How many people will be invited if this process continues for four rounds?
March 31, 2009
the zero input response of a series RLC circuit with R=80 ohms is V(c)=2e^(-2000t)cos(1000t)-4e^(-2000t)sin(1000t) V for t>0 if the initial conditions remain the same, what is the zero-input response when R=40 ohms
March 23, 2009
Write balanced equations for the formation of [Ni(NH3)6][BF4]2 starting from an anhydrous sample of nickel(II) choride hexahydrate. (3 equations necessary) I am slightly confused by this. I think the starting sample has the formula [Ni(H20)6]Cl2 Would this react with ammonia...
March 11, 2009
I think that nickel(II) nitrate has the formula Ni(NO3)2. As we are starting from anhyrdrous nickel nitrate I thought the first step might be to hydrate it Ni(NO3)2 + 6H2O --> [Ni(H2O)6](NO3)2 and then I thought a reaction with potassium thiocyanate KSCN but I am not sure ...
March 11, 2009
body of mass 7 kg moves in a (counterclockwise) circular path of radius 4 meters, making one revolution every 13 seconds. You may assume the circle is in the xy-plane, and so you may ignore the third component. how do you find the centripetal force acting on the body how do ...
February 18, 2009
A gun has a muzzle speed of 90 meters per second. What angle of elevation should be used to hit an object 180 meters away? Neglect air resistance and use 9.8m/s^2 as the acceleration of gravity.
February 18, 2009
What is the pH of a solution made up of 50cm^3 of 1M Ethanoic Acid and 25cm^3 of 1M sodium ethanoate? Assume Ka for Ethanoic acid is 1.8 x 10^-5 mol dm^-3 I'm not quite sure how to do this. I was going to use the equation pH = pKa + log[A-]/[HA] but it doesn't seem to ...
February 16, 2009
Tank 1 initial contains 70 L (liters) of water and 450 g of salt, while tank 2 initially contains 20 L of water and 200 g of salt. Water containing 10 g/L of salt is poured into tank1 at a rate of 1 L/min while the mixture flowing into tank 2 contains a salt concentration of ...
February 6, 2009
What does Pablo Neruda refer to in the last verse of his poem "La Anaconda Copper Mining Company"? "Y hay una y otra cruz torcida en las laderas infernales como única leña dispersa del árbol de la minería."
February 6, 2009
A particle rotates in a circular orbit about a point located 30cm away, with angular speed 2 rad s^-1. If the angular momentum is 0.2 Js, determine the mass of the particle. I used L=mr^2 omega and got 1.11kg A constant torque of 0.2Nm accelerates the particle for 5s. ...
February 2, 2009
The cell Pt|H2(1 bar)|HCl(m)|AgCl(s)|Ag has an Stadard elctrode potential value of 0.2224V at 298K Using the Nernst equation, calculate a value for the EMF when the HCl concentration is 0.20M. I know what the Nernst equation is but I am unsure how to use it when I only have ...
January 14, 2009
AP World History
Well we are doing a project on empire building and we had to answer a couple of questions. I looked all over the internet and I can't find answers to these four questions. this is due tomorrow so I'm really desperate. Can someone help me out? My empire is the Spanish ...
January 11, 2009
One mole of nirtogen at 273K occupying 10 litres (state 1) is to be expanded to a volume of 20 litres at 373K (state 2). An infinite number of paths from state 1 to state 2 are possible. Consider the following important paths: (a) The gas is expanded isothermally and ...
January 8, 2009
I'm supposed to write a paper on the "real" reason behind not running in the house. It's just why you think you shouldn't run in the house, just something funny nothing real. What should I say is the reason, that will make my class laugh?
January 7, 2009
A conductivity cell was calibrated using KCl solution (0.01 mol dm^-3) with a conductivity of 0.141 S m^-1 and the resistance was found to be 520 Ohms. The resistance of a saturated solution of silver chloride was found to be 3.8 x 10^5 Ohms. Calculate the solubility product ...
January 4, 2009
Which phosphates are found in human urine? I am writing about the discovery of phosphorus. I know that after urine was left to stand for several days and boiled to a paste it contained ammonium sodium hydrogen phosphate. Is this a constituent of fresh urine or did a reaction ...
January 4, 2009
Write a differential equation describing a second order reaction a reaction in which the rate of depletion of the concentration of the reactants depends on the square of reactants concentration. Solve this differential equation and hence find an expression for the...
November 10, 2008
P=(2J+1)exp(-(BJ(J+1))/kT) where B, k and T are constants a. Show that dP/dJ=(2-(B(2J+1)^2)/kT)exp(-BJ(J+1)/kT) b. Show that P exhibits a maximum and determine the expression for Jmax c. Find the value of P when J=0 and the limiting value of P when J becomes large(infinity).
October 28, 2008
Ok, I am not sure how to about about solving this problem and have been staring at it and drawing pictures for several hours now. Do I use the spring equation for potential energy? Or is it a momentum problem where I should assume the spring has it's own velocity? Any help...
October 19, 2008
Transform the following relationships/funtions into linear form and identify expressions for the x and y variables. a) (x^2/a^2) + (y^2/b^2) = 1 where a and b are constants. b) k(T) = (kT/h)exp((deltaS)/R)exp(-(deltaH)/RT) where k, deltaS, deltaH and R are constants.
October 18, 2008
I have worked out that the element is nitrogen and the first hydride is NH3. I calculated the second hydride to have the empirical formula NH2. Would the molecular formula be N2H6? I'm not too sure about the structures.
September 2, 2008
year 7 geography
research which instruments are needed to measure which feature of the weather Temperature , Precipitation , Cloud cover , Cloud type , Wind direction , Wind speed , Visibility. The example i have got is visibility - eyes and instruments Does the question mean you have to put ...
June 2, 2008
OK I understand the concept present value but I don't understand how to solve for present value in this context: Assume that you won a local contest for which you gain a continuous income stream at a rate R(t)=5000e^0.1t per year for 5 years and r=0.05. Find present value...
April 29, 2008
Can anyone help me with this problem? Suppose that during a controlled experiment, the temperature in a beaker containing some chemical substance at time t is rising at a rate of (15/13)t^2-(7t) degrees centigrade per minute. If the temperature after 1 minute is measured to be...
April 22, 2008
Yesterday, I saw Martin Luther sitting on top of a large pumpkin. A cabbage fell from the sky and hit him in the head. Martin Luther was angry and swore at the cabbage. Most people do not know this, but Ralph Waldo Emerson is still alive. He was found buried under a layer of ...
April 12, 2008