 # wolfson

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## Everything posted by wolfson

1. ## Why is the pH of pure water i.e. neutral 7?

In pure water, the hydrogen ion (hydroxonium ion) concentration must be equal to the hydroxide ion concentration. [OH-] term in the Kw expression by another [H+]. [H+]2 = 1.00 x 10-14 Taking the square root of each side gives: [H+] = 1.00 x 10-7 mol dm-3 Converting that into pH: pH = - log10 [H+] pH = 7
2. Example 2: How much copper is deposited if a current of 0.2 Amps is passed for 2 hours through a copper(II) sulphate solution ? Electrode equation: (-) cathode Cu2+(aq) + 2e- ==> Cu(s) and Ar(Cu) = 64 the quantity of electricity passed in Coulombs = current in A x time in secs (Q = I x t) = 0.2 x 2 x 60 x 60 = 1440 Coulombs, and 1 mole electrons = 96500 Coulombs therefore moles of electrons passed through circuit = 1440 / 96500 = 0.01492 it takes two moles of electrons to form one mole of copper therefore moles copper = 0.01492 7 2 = 0.00746 mass of copper = moles of copper x atomic mass of copper = 0.00746 x 64 = 0.4775g of copper deposited. Taken from http://www.wpbschoolhouse.btinterne...lysis%20product
3. The mass of a substance produced at an electrode during electrolysis is proportional to the quantity of electricity that has passed. Look up, Faraday's formula to relate these variables. look at site below: http://www.wpbschoolhouse.btinternet.co.uk/page04/4_73calcs.htm#13.%20Electrolysis%20product
4. Melting point of diamond = 3815.56oC, thats about 2.5 times more than steel. This information is the correct. Ref: RSC.
5. Sulphuric acid at that temperature will rapidly corrode steel.
6. Pulkit that was so wrong it's not even funny: Na2SiO3 + 8 HF --> H2SiF6 + 2 NaF + 3 H2O
7. To a chemist, that seems to me as a spelling mistake for Sialic Acid.
8. infinity = The limit that a function is said to approach at x = a when (x) is larger than any preassigned number for all x sufficiently near a.
9. I wrote a bit on electronic config at: http://dragonslair.europe.webmatrixhosting.net/Science/Chemistry/Eleccon2.htm It should help.
10. If all you wish to do is measure the number of mols, the easiest way would be to just weight the gas. weight the gas = calculate the volume. The higher the temperature the faster molecules are moving. Faster the molecules = higher the pressure, as are moving, the harder they hit the wall of the container. It's all kinetic theory/motion.
11. petrol heat of combustion:5460 kj/mol LPG heat of combustion 2220 kj/mol 2 C8H18 + 25 O2 = 18 H2O + 16 CO2 (combustion of octane) CH3-CH2-CH3 + 5 O2 = 3 CO2 + 4 H2O (combustion of propane) 1 mole of propane combusts 2 mole of Octane combusts Octane uses 10920 Kj Propane uses 2220 Kj So if Octane is 80 cents per 10920Kj Octane = 80 / 10920 = 0.00733 cents per Kj You get 2 moles of propane for the equivalent of octane So 0.00733 / 2 = 0.0037 So 0.0037 cents per kj And 2220 kj = 8.2 cents I am not sure if this is correct, it’s early in the morning
12. A list of metals arranged in order of their electrode potentials. A metal will displace, from their salts, metals lower down in the series. Lithium Potassium Calcium Sodium Magnesium Aluminum Zinc Iron Cobalt Nickel Tin Lead ---------------- Hydrogen ---------------- Copper Mercury Silver Platinum Gold
13. The norm H =37.1 pm The norm He(1+) = 31 pm
14. The process for preparing stable high oxidation state ferrocene derivatives, namely Fe(III)/Fe(IV), by reacting ferrocene derivatives in which one or more electron-donating groups are covalently bonded to the cyclopentadienyl rings with electron-donating ligands having strong coordinative groups for ferric species. (APP 2001)
15. Allot of people who I am teaching at Summer college at University seem to be struggling with chemistry for applied science I think there are a number of factors the major is a giant step up from A-Level applied science to Undergraduate, the laboratory reports seem to be proving difficult for some. Also the grasp of equilibrium (Kc) and intermolecular forces. But hopefully with a bit of help from me they should start to realize the relationship between them.
16. 1 - The Summary Graph 2 on Page 4. This is the function which needs completion by calculus. -------------------------------------------------------------------------------- I've just had a quick look at your website and found the graph, but what is the function? Could you post the function explicitly here? Sorry if I've missed something, but I'm confused as to what you are asking.
17. Assuming I am still correct... Then there will be a meeting of great prof's to all talk and see if it correct. and then.......... well maybe on tv. Or get some king of an award. But i'd put it on scienceforums on here, remember you still wrote it first so its yours, and you'll have all your workings out.
18. Sometimes we think of sides as having to be flat - what mathematicians call "faces" of a polyhedron. In that sense, a sphere has no sides (though some people will try to convince you that it has infinitely many sides). I think the most applicable definition is the one used in topology. We talk about surfaces with two sides (like a piece of paper) and surfaces with only one side (like the Moebius strip you may have heard of). In this sense, and remembering that mathematicians define a sphere as the surface of a sphere, not a solid ball, I would say that a sphere has two sides: the outside and the inside. (ref: Dr P. APP)
19. ## whats the chances of alien life form more intelligent than us?

Well said Jakiri.
20. and does it block gamma rays? I very much doubt it.
21. 