Search results for query: *

  1. K

    Stability of Lead Iodide

    Thank you! Do you think that would apply to Potassium Iodide solid too?
  2. K

    Stability of Lead Iodide

    About 6 years ago, I made a precipitate of Lead Iodide in water by mixing Potassium Iodide and Lead Nitrate. I have kept the precipitate in a test tube. Would anybody know how stable is the precipitate over time. The temperature has been mostly between 20 and 32 degrees depending on the...
  3. K

    How to measure formaldehyde?

    hi. may i know why NaOH has to be added? - just asking! thnks
  4. K

    Why don't lakes freeze solid?

    the layer of ice formed above acts as an insulator to minimise further freezing downwards.
  5. K

    Oxidizing power of potassium chlorate vs. nitrate

    oooops... yeah it is ClO3-
  6. K

    Oxidizing power of potassium chlorate vs. nitrate

    i have some standard electrode values. OCl^{-}_{(aq)} + H^{+}_{(aq)} + e^{-} \Leftrightarrow \frac{1}{2}Cl_{2(aq)} + 2H_{2}O_{(l)} emf = + 1.64 V NO^{-}_{3(aq)} + 3H^{+}_{(aq)} + 2e^{-} \Leftrightarrow HNO_{2(aq)} + H_{2}O_{(l)} emf = + 0.94 V therefore, the...
  7. K

    An interesting Contest

    thanks for sharing...:)
  8. K

    Is SO3 Soluble in Water?

    awwww ok... lol... i didn't think of it as sarcastic... i thought there really were solutions of SO3 dissolved in water. haha, thnks anyway
  9. K

    Is SO3 Soluble in Water?

    noo... i don't think they have those in high school labs!
  10. K

    Is SO3 Soluble in Water?

    Is SO3 soluble in water?? i know it reacts very exothermically with water to form water soluble products (H2SO4). But is SO3 itself soluble in water?
  11. K

    Can we predict a complex molecule's shape?

    proteins are very complex molecules. but i think it would not be impossible to predict the molecular shape of glucose or an amino acid. you just have to start systematically, say from one of the Carbon atoms, and proceed then with the other bonds. These molecules do not have too many atoms.
  12. K

    Can we predict a complex molecule's shape?

    can you give me an example of what you mean by a complex molecule? theoretically you can, by analysing the lone pairs present, the number of bond pairs and using the electron repulsion theory.
  13. K

    Zinc and Hydrochloric Acid

    yeah... thank you for posting the actual mechanism :)
  14. K

    Zinc and Hydrochloric Acid

    Zn, HCl and CuSO4 works, i remember my teacher saying it. and of course ZN++ does not REACT with Cl-, the ions remain in solution because ZnCl2 is a strong electrolyte. but there has to be a way for Cu to get back to Cu++ and H+ to get to H2. chemisttree heeelp!
  15. K

    Zinc and Hydrochloric Acid

    i guess this is what happens... the Cu++ is reduced by zinc to Cu and the zinc is oxidised to Zn++. the Zn++ reacts with the Cl-. the Cu is then oxidised back to Cu++ by H+ which gets reduced to H2 overall reaction: Zn + 2HCl -----> ZnCl2 + H2
  16. K

    Need Help With Chemistry Past Paper 2?

    from which exam board? you can google for AQA past papers easily...
  17. K

    Increasing acidity n basicity

    you also have to consider atoms such as chlorine which induce a -I effect on a benzene ring affecting basicty...
  18. K

    Freezing point depression

    this might be a silly answer but, maybe it is because when NaCl dissolves, it breaks some H-Bonds, to form ion-dipole attractions. this then lowers the melting point of ice.
  19. K

    Structure of Atom 117 & 119

    i don't really know, but most probably, element 117 would ressemble the halogens.
  20. K

    Hess's Law

    basically it says that, the enthalpy change of a reaction depends only on the initial and final conditions of the reactants and products respectively. the reaction route or reaction pathway has no effect on the enthalpy change. a quick example is when you produce CO2 from Carbon and oxygen...
  21. K

    Alcoholic question

    alcohols are neutral but can be made to react amphoterically (as acids or alkalis), depending on the conditions.
  22. K

    Silicon-oxygen tetrahedron

    there is covalent bonding. it is a macromolecule. and has very high melting point, it should be quite stable then, at least thermally... i'm assuming you are talking about SiO2, because i never heard of SiO4. i kno that SiO2 is just the ratio of Si to O, and that SiO4 units are joined together...
  23. K

    Experiment outline on Tap Water vs Bottled Water

    you might also find a way to test for bacteria or germs (or living organisms in general) present. i dunno, maybe using microscopes??! and for minerals and nutrients?? do plants getting tap water or bottled water grow differently?? if you store tap water and bottled water in a certain recipient...
  24. K

    Convert a given alkane to any higher or lower alkene without sides rxn

    there is the cracking of large alkane molecules, to give smaller ones in the petroleum industry. you only need a catalyst, silica or alumina, and a temperature of about 450 degrees. for converting lower alkanes molecules to larger ones, i have no clue.
  25. K

    Periodic table in another planet

    no, i don't think so. the elements in the periodic table exist throughout the universe. except the man made ones. now, if the question is asking for elements present on another planet, then it might not be as much as many as found here. or you might even have elements which are not found on...
  26. K

    How much oxalate?

    everything foodstuff can be dangerous to us; this is what books say. of course it's about the quantity. you'd believe that chocolate could cause cancer?? i don't know about the quantities though.
  27. K

    Solubility of compound in solutions other than Water

    actually BaCO3 and BaSO3 react with the acid, to give CO2 and SO2 respectively. BaSO4 doesn't react. You may think of it like H2SO4 is a stronger acid than HCl, hence the HCl cannot displace the SO42-. and i agree with symbolipoint about the complexes.
  28. K

    Identification of group 2 metal salts

    o yeah, of course, X is NOT BaSO4, i will correct that right here. i think more information is required. sorry
  29. K

    Delta Heat of Formation

    if I'm not wrong, this reaction ain't supposed to be occurring. H2 will not react with Cu2+. you can't determine enthalpy change of formation in this reaction. the enthalpy change of formation is when 1 mol of a compound is produced from its elements in their elemental states. e.g. enthalpy...
  30. K

    Identification of group 2 metal salts

    AgNO3 will help you to find out if there are halide ions (chloride, iodide, bromide,..) in the salts X and Y. BaCl2 will tell you if sulphate is present. These two tests determine the anions. the test with NaOH will help to distinguish the cation. and i think Y is MgCl2 or MgSO4. you will...
  31. K

    REDOX titration of bleach help

    iodide from excess KI is a reducing agent, it is oxidised by the hypochlorite ion to iodine. Iodine is an oxidsing agent. The iodine liberated will then oxidise the thiosulphate. Iodine is normally brown when in solution. actually it reacts with iodide from the excess KI to form tri iodide...
  32. K

    Which pair of elements is most apt to form an ionic compound

    hydrogen bonding is an INTERMOLECULAR FORCE (even if we call it H-bond), it occurs between molecules, such as water or ammonia. it is in no way an actual bond. actually electronegativity sums the atomic size. The fatter the atom, the smaller is the electronegativity and vice versa.
  33. K

    Abundance of isotopes

    i suppose you have to calculate the atomic mass of the element??! huh let's take the example of chlorine, which has two istopes too. Cl-35 and Cl-37, in the ratio of 3:1. on average, chlorine atoms have atomic mass of: [(35 * 3) + (37 * 1)] / 4 similarly, you can calculate the atomic...
  34. K

    Which pair of elements is most apt to form an ionic compound

    one way to look at it involves electronegativity. For a bond to be ionic, difference in electronegativity should be greater than 1.7 electronegativity of N is 3.0, and that of hydrogen is 2.2 the difference is less than 1.7 electronegativity of barium is 0.89 and that of bromine is 2.96...
  35. K

    Brine electrolysis: question

    what IS the second experiment?? as far as i remember, the only way for graphite to become unusable is through oxidation; but here Cl- is preferentially you wouldn't get oxygen... i believe you can still use the grphite electrode... as long as Cl- is found in a greater...
  36. K

    Transmutation: What Is It?

    all i know about alchemy is from paolo coelho's book, the alchemist. it's supposed to be an ancient art with two main objectives, still not yet accomplished. these are: 1) making the immortality potion 2) turning lead into gold
  37. K

    Moles and atomic weights

    The unified atomic mass unit (u), or dalton (Da), is a small unit of mass used to express atomic and molecular masses. It is defined to be one twelfth of the mass of an unbound atom of the carbon-12 nuclide, at rest and in its ground state. from wikipedia... couldn't be of much greater help...
  38. K

    Caffeine from coffee

    ethyl acetate can be synthesized from a simple esterification reaction. all you need is ethanol and ethanoic acid as reagents. Conc. sulphuric acid will be needed as catalyst(a few drops only). and yes, you will have to perform this under reflux while heating the mixture.
  39. K

    Help on the bonding of LiAlH4

    there is an ionic bonding when you consider Li+ and AlH4- but, AlH4- is itself a covalent anion. there are 3 Al-H covalent bonds in this molecule... but AlH3 still has a vacant sub-orbital... coordinate covalent bond occurs... an H- bonds with the AlH3 forming AlH4-
  40. K

    Is there any difference between Miscible and Soluble?

    maybe I'm wrong, but, when a substance dissolves, there is an energy change, e.g for NaCl to dissolve in water at rtp, the Delta H is +5kJ/mol but for miscible substance I'm pretty sure there's no energy change... because the molecules only get between each other...
  41. K

    Oxidation numbers

    hey... just to point out that such reactions, where a species is at the same time reduced and oxidised, is called a disproportionate reaction. cheers
  42. K

    Neutralization Reaction

    neutralisation involves rxn between H+ and OH- whenever there is a rxn between an acid and a base, it is always a neutralisation one! moreover, a weak acid will ionise completely during neutralisation. as the OH- reacts with the H+ from the weak acid, the latter H+ decreases in...
  43. K

    Electroconductive gel

    the gel should not be sooo dirty like grease! I've got no exact purpose for this gel, jjust wanted to kno how to make it!
  44. K

    Electroconductive gel

    hey guys, i need to make an electroconductive gel. e.g silver chloride gel! please help me. thnks
  45. K

    Why the bond angle of methane is 109 instead of 90?

    methane consists of four bonded pairs, i.e 4 C-H bonds. So as to minimize repulsion, the molecule adopts a tetrahedral shape, hence bond angle becomes 109.5. with bond angle of 90, the molecule would not be very stable.