# Search results

1. ### Limits using basic analysis theorems and logic?

I solved it thus: (n^2 + 2n)^1/2 = (n^2)^1/2 * (1+2/n)^1/2 therefore this = n(1+2/n)^1/2 now expand the bracket using taylor's theorem to get (1+2/n)^1/2= 1+(1/n)-(1/n^2)+... therefore multiplying by n in the above you have n+1-(1/n) as n tends to infinity the (1/n) becomes...
2. ### PH calculation

I have a short question concerning the dilution of a 0.01M solution of HCN. I need to dilute 40cm3 of the above to give a solution with a pH of 6. Given the Ka of HCN is 4.8*10^-10 I obtain the concentration of HCN necessary in the new volume:2.08*10^-3M. Therefore the volume has to be...
3. ### Meteorite heading towards earth

Hi ppl. I have a short question. A meteorite of mass m has a velocity u=2.00*10^4 m/s when it is at an infinite distance from the earth. It eventually collides with the eath with a velocity v. Calculate v. given are the radius of earth(6.37*10^6m) and go=9.80Nkg^-1) I used the argument that...
4. ### Working out the ph of CH3COONa

Hi ppl. I have a question. I'm given the pka of ethanoic acid/ethanoate ions at 4.75 and i have to work out the ph of a 5*10^-2 moldm3 solution of sodium ethanoate. I worked it out by getting the Ka from 10^-4.75 and then saying that the concentration of Ch3COO- in the dissociation of ethanoic...
5. ### Calculate e

The way I was introduced to e was to try to find the exponentional which was its own derivative. So say we have a^x, we know that a^0 is 1, so try to find the value of a such that the gradient of a^x is 1 at the point (0,1). From this you get the definition of a, or as we know it e: Lim...
6. ### Equalibrium Problem

Hi my friend. What you should do here is write first the equilibrium reaction for these two substances ionisation in water, then deduce an expression for Kc-eqm constant. This expression will include the concentration of water, which is constant and thus cancels out of the equation. Then replace...
7. ### Predicting a reaction between ester and acyl halide

HI ppl, I have a question here. I deduced a forumla of an acid, aminobenzoic acid and this reacted with ethanol to give the corresponding ester. This ester then reacts with an acyl halide, CH3COCl, any ideas as to the product of this reaction??? Thanks, Joe
8. ### Nitrogen Organic

Hi ppl, I have this question. I have the MF of a substance A : C7H7O2N. I have three pieces of info which should indicate a structural property of this substance:i) A reacts with sodium carbonate to give off CO2. I thought this might indicate an ionic structure? then ii) A will form a coloured...
9. ### Range of Validity

Hi ppl. May I ask how you obtain the range of convergence for the maclaurin expansion of ln(1-x) and taylor's series, maclaurin's in general? Thanks, Joe
10. ### Alpha Emission

Here I have a problem: A 232/92 Uranium nucleus emits an alpha particle with kinetic energy=5.32MeV. What is the final nucleus and what is the approximate mass(in units) of the final atom. I can write the equation for the reaction, this will give 4/2 He and 228/90 Th. If the alpha particle...
11. ### Alpha Emission

Here I have a problem: A 232/92 Uranium nucleus emits an alpha particle with kinetic energy=5.32MeV. What is the final nucleus and what is the approximate mass(in units) of the final atom. I can write the equation for the reaction, this will give 4/2 He and 228/90 Th. If the alpha particle...
12. ### How to get started on this?

I used the fact that delta(y) is roughly equal to delta(x) times dy/dx. Then you come up with y(3)-y(1)=(e^1/1)(3-1). I think this gives y(3)= 2e+2. Could someone verify that this is the correct approximation? Thanks, Joe
13. ### Limit proof

You might also remeber to use the maclaurin's series for sinx. since sinx= x-x^3/3! + x^5/5! the x's will cancel and give 1 and the rest of the terms in x will become negligible for the given limit as x tends to zero, Joe
14. ### Volumetric estimation of iron(II)ions

Hi ppl, I have an electrochemisry question. Explain why dilute sulphuric acid, rather than dilute hydrochloric acid, is used as a source of hydrogen ions in the volumetric estimation of iron (II) ions with potassium manganate (VII).
15. ### Redox reactions and oxidation

Hi ppl. I'm asked a question: Iron filings are added to a solution containing the ions Cu2+, Fe2+, Fe3+, H30+ and Zn2+. Deduce what reactions occur from the standard electrode potentials. Is this simply asking me which will change Fe2+ to Fe3+ and vice-versa by reduction or oxidation do you...
16. ### Electrochemistry question

Hi people, I have the following question. Fe2+, Fe3+, Cr2O7(2-) and Cr3+ are contained in a solution in standard states with dilute sulphuric acid. Deduce what happens. I am wondering here what effect the sulphuric acid has, is it simply a catalyst for the reaction in which the Cr2O72- is...
17. ### De Broglie wavelength and diffraction

Hi ppl I have a short question concerning the de Broglie hypothesis. I worked out the de Broglie wavelength of an electron in a TV picture tube accelerated by 20,000 V, using the fact that mv^2/2 = QV and then that lambda=h/mv. Now I need to answer whether this is relativistic or not, how do I...
18. ### Find the minimum velocity

The reason I took 2r as the denominator is that GMm/2r is the total energy of the satellite at that position in orbit, whereas GMm/r is just the potential.... Is this correct?
19. ### Velocity selector

Hi ppl, I'm having a little trouble determining the direction of the E field in a velocity selector question. I can easily find the direction of the magnetic B field and the direction it forces a particle in. Once I do this, I know that the E field must oppose the force of the B...
20. ### Find the minimum velocity

Hi ppl, could someone just clarify this for me i need to find the minimum velocity that the satellite meteosat (time period is 23h56min and altitude is 35800km + radius of earth(6370km)) must be given to escape from the force of attraction of the Earth. I started by saying that the total...
21. ### Differential Eqns

The problem I have now is seeing what the equation does as t tends to infinity, e^-t will tend to zero, but e^2t will just tend to infinity while cost and sint are periodic, could you help me with this please? Joe
22. ### Differential Eqns

ok, I have my general solution: x: Ae^2t + Be^-t +cost -3sint putting in x=4 and t=0 I obtain 4=A+B+1 so 3=A+B and A=3-B So My final solution is: x=(3-B)e^2t +Be^-t +cost -3sint Is this correct, could someone verify? How about the fact that t tends to infinity, does this...
23. ### Differential Eqns

Can anyone offer some advice on this problem: Obtain a general solution for the second order differential equation: (d^2x/dx^2) - (dx/dt) - 2x = 10sint I obtained the general solution and now need to determine the "solution which remains finite as t tends to infinity for which x=4 at...
24. ### Incandescent light

hi ppl, I was wondering. In a double slit experiment, we fire light rays through two slits using two incandescent lamps. Would the interference phenomenon be observed? I thought no, is it to do with the wavelength of incandescent light being outside the spectrum? Could someone help...
25. ### Is propanoic acid stronger than ethanoic?

Thanks a lot for the help, my friend, I very much appreciate it. I have just to clarify about the chromate though: I need to give the equation for the reaction that produces the colour change, an unbalanced one. All I know is that it involves the Cr3+, could you please suggest the other...
26. ### Is propanoic acid stronger than ethanoic?

Hi ppl, Is propanoic acid stronger than ethanoic?Because propanoic acid has a longer R-group, it will have a greater inductive electron releasing effect than ethanoic acid, so the electron density is greater in propanoic acid than for ethanoic acid. With a region of greater e density...
27. ### Equation a^b=b^a

Hi ppl, could someone offer some help on the following problem: Obtain real values for a and b which satisfy the equation a^b=b^a I took the logs of both sides to give bloga=alogb Is there any way of simplifying the equation from here? Joe
28. ### Waves questions for homework

okay, for the first question, I have managed to work it out myself having calculated the new wavelength. For the others, it's how to set up an equation bearing in mind the condition for destructive interference that I can't work out.
29. ### Waves questions for homework

Hi ppl, could someone plz give me a hand with these: Light of wavelength 400 nm in air falls on two slits 0.05 mm apart. The slits are immersed in water, as is a viewing screen 40cm away. How far apart are the fringes on the screen?(n water is 1.33) In a double slit experiment it is found...
30. ### Wave questions

Hi ppl, could someone plz give me a hand with these: Light of wavelength 400 nm in air falls on two slits 0.05 mm apart. The slits are immersed in water, as is a viewing screen 40cm away. How far apart are the fringes on the screen?(n water is 1.33) In a double slit experiment it is found...