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Monday, May 9

  1. msg Air Pollution message posted Air Pollution Really? Are developing countries such as China and India which are producing many goods at a fast r…
    Air Pollution
    Really? Are developing countries such as China and India which are producing many goods at a fast rate doing so without high levels of air pollution? Are they using greener technology?
    3:24 am

Saturday, May 7

  1. page Water (HL) edited ... --> In a saturated solution: ZnS(s)<--> Zn2+(aq) + S2-(aq) Ksp [Zn2+][S2-] 1…
    ...
    -->
    In a saturated solution: ZnS(s)<--> Zn2+(aq) + S2-(aq)
    Ksp
    [Zn2+][S2-]
    1.60 x 10-24
    ...
    The equilibrium constant for this reaction, Kc, can be deduced from the equilibrium law as:
    { [Hg2+ (aq)] [S2-(aq)] } / [HgS(s)]
    Ksp = [Hg2+[Hg2+ (aq)] [S2-(aq)]
    Given the equilibrium formed by a metal M and a non metal X:
    MX(s) <--> M+(aq) + X-(aq)
    (view changes)
    3:41 am
  2. page Water (HL) edited ... Heavy Metals Heavy metals are serious water pollutants because the are toxic. The heavy metal…
    ...
    Heavy Metals
    Heavy metals are serious water pollutants because the are toxic. The heavy metal ions of mercury, lead and cadmium interfere with the behaviour of other necessary ions in body such as
    ...
    , Mg2+ andand Zn2+
    Even very small traces of heavy metals can have very significant harmful effects.
    The table below summarizes the sources of each of these pollutants and their possible health and ways to reduce the pollutant-
    ...
    The equilibrium constant for this heterogeneous eqilibrium is called the solubility product, Ksp.
    Ksp is called the solubility product constant (note: the concentration of solid does not appear because it is also a constant) and, because Ksp is temperature dependent, the particular temperature at which it is measured must be quoted. Thus, in a saturated solution of a slightly of a slightly soluble ionic compound, the product of the concentrations of the individual ions raised to the powers indicated by the coefficients is a constant at a given temperature. Precipitation depends on Ksp; a precipitate will form if the product of the ions in the mixture of solutions, when substituted into the Ksp expression, exceeds the numerical value of Ksp at that temperature.
    The very insoluble salts in aqueous solution will have very small values for Ksp. For example, theExample:
    Zinc(II) ions (Zn2+) can be removed by bubbling hydrogen sulfide through polluted water. The
    solubility product of silver chloridezinc sulfide is equal to 1.81.60 x 10-1010-24 mol2dm-6 at 298K. The value25
    ⁰C.
    Calculate the concentration
    of Zn2+ ions in a saturated solution of zinc sulfide.
    -->
    In a saturated solution: ZnS(s)<--> Zn2+(aq) + S2-(aq)
    Ksp
    [Zn2+][S2-]
    1.60 x 10-24
    When no other ions are present: [Zn2+] = [S2-]
    [Zn2+]2 = 1.60 x 10-24
    [Zn2+] = {file:///C:/DOCUME%7E1/Ruchidra/LOCALS%7E1/Temp/moz-screenshot-6.png} 1.26 x 10-12 mol dm-3
    The example shows that an increase in the concentration of sulfide ions lead to a decrease in
    the solubility productof the zinc ions in solutions. This is related toa general result known as a common ion effect.
    Consider,
    the solubility of calcium phosphate:
    Ca3(PO4)2(s) <--> 3Ca2+(aq) + 2PO43-(aq)
    An increase in
    the salteither phosphate ions or calcium ions, that is ions common to the compound and the added solution, will - according to the Le Chatelier's Principle- shift the equilibrium to the left and decrease the solubility of the compound.
    Summary:
    Metal ions are removed from solution by chemical precipitation as a sparingly soluble salt.
    Hg2+(aq) + H2S(aq) --> HgS(s) + 2H+(aq)
    The insoluble sulfides
    can also be calculated givenformed when a soluble sulfide is added.
    Pb2+(aq) + S2- --> PbS(s)
    Some metals can be removed as insoluble hydroxides on
    the valueaddition of Ksp:aqueous sodium hydroxide.
    Cr3+(aq) + 3OH-(aq) --> Cr(OH)3(s)
    Some metals can be removed as insoluble phosphates.
    Al3+(aq) + PO43-(aq) --> AlPO4(s)
    A dynamic equilibrium is set up between soluble and the aqueous ions. Consider, for example, mercury sulfide:
    HgS(s) <--> Hg2+(aq) + S2-
    The equilibrium constant for this reaction, Kc, can be deduced from the equilibrium law as:
    { [Hg2+ (aq)] [S2-(aq)] } / [HgS(s)]
    Ksp = [Hg2+ (aq)] [S2-(aq)]
    Given the equilibrium formed by a metal M and a non metal X:
    MX(s) <--> M+(aq) + X-(aq)
    The Keq for this system is given by Ksp = [M+][X-}, and is called the solubility product constant. Ksp depends only on temperature.

    Bibliography-
    1)Introduction- Cartin Brown, Mike Ford, (2009). Retrieved on April 5, 2011. From- Pearson Baccalaureate Chemistry Developed specifically for the IB Diploma.
    (view changes)
    3:39 am
  3. page Water (HL) edited ... Heavy Metals Heavy metals are serious water pollutants because the are toxic. The heavy metal…
    ...
    Heavy Metals
    Heavy metals are serious water pollutants because the are toxic. The heavy metal ions of mercury, lead and cadmium interfere with the behaviour of other necessary ions in body such as
    Ca2+, Mg2+, andCa2+ , Mg2+ and Zn2+
    Even very small traces of heavy metals can have very significant harmful effects.
    The table below summarizes the sources of each of these pollutants and their possible health and ways to reduce the pollutant-
    ...
    Decreased lung function, aggravation of asthma, development of bronchitis, emphysema and respiratory cancer.
    Electrostatic precipitation
    ...
    be removed from water during
    The removal of metal ions from solution by chemical precipitation, in which the metal is removed as a sparingly soluble salt. The so-called insoluble salts such as silver chloride dissolve to a very small extent in water, so not all heavy metals will be precipitated out.
    Hydrogen sulfide (
    H2S)
    (H2S) can be
    Hg2+(aq) + H2S (aq) --> HgS (s) + 2H+ (aq)
    {mercury.gif}
    (view changes)
    1:55 am

Wednesday, May 4

  1. page Acid Deposition (HL) edited ... Oxides of Nitrogen One reason for acid deposition is the formation of oxides of nitrogen, NOx…
    ...
    Oxides of Nitrogen
    One reason for acid deposition is the formation of oxides of nitrogen, NOx. Nitrogen oxides form for a variety of reasons, one being lightning strokes. The high temperature caused by the lightning stroke causes the nitrogen and oxygen in air in it's vicinity to react and form nitric oxide, NO. The nitric oxide then reacts very quickly to the surrounding oxygen in the air, thus forming nitrogen dioxide.
    {Acid.GIF} {Acid.GIF}Fig. 1 - Formation of nitrogen oxides {Acid.GIF} [Fig. 1]
    In the case of acid rain, the nitrogen dioxides would react with the rain water to form nitrous acid, HNO2, and nitric acid, HNO3. Due to these acids forming from the reaction between nitrogen dioxide and rainwater, it causes the rainwater to have a lowered pH, thus resulting in acid rain.
    {Acid_Rain.GIF} [Fig. 2] Formation of nitric acid
    (view changes)
    4:18 pm
  2. page Acid Deposition (HL) edited ... Oxides of Nitrogen One reason for acid deposition is the formation of oxides of nitrogen, NOx…
    ...
    Oxides of Nitrogen
    One reason for acid deposition is the formation of oxides of nitrogen, NOx. Nitrogen oxides form for a variety of reasons, one being lightning strokes. The high temperature caused by the lightning stroke causes the nitrogen and oxygen in air in it's vicinity to react and form nitric oxide, NO. The nitric oxide then reacts very quickly to the surrounding oxygen in the air, thus forming nitrogen dioxide.
    {Acid.GIF}
    {Acid.GIF}
    {Acid.GIF} [Fig. 1]
    In the case of acid rain, the nitrogen dioxides would react with the rain water to form nitrous acid, HNO2, and nitric acid, HNO3. Due to these acids forming from the reaction between nitrogen dioxide and rainwater, it causes the rainwater to have a lowered pH, thus resulting in acid rain.
    {Acid_Rain.GIF} [Fig. 2] Formation of nitric acid
    (view changes)
    4:16 pm
  3. page Acid Deposition (HL) edited ... Oxides of Nitrogen One reason for acid deposition is the formation of oxides of nitrogen, NOx…
    ...
    Oxides of Nitrogen
    One reason for acid deposition is the formation of oxides of nitrogen, NOx. Nitrogen oxides form for a variety of reasons, one being lightning strokes. The high temperature caused by the lightning stroke causes the nitrogen and oxygen in air in it's vicinity to react and form nitric oxide, NO. The nitric oxide then reacts very quickly to the surrounding oxygen in the air, thus forming nitrogen dioxide.
    {Acid.GIF}
    {Acid.GIF} [Fig. 1] Formation of nitrogen oxides
    In the case of acid rain, the nitrogen dioxides would react with the rain water to form nitrous acid, HNO2, and nitric acid, HNO3. Due to these acids forming from the reaction between nitrogen dioxide and rainwater, it causes the rainwater to have a lowered pH, thus resulting in acid rain.
    (view changes)
    4:16 pm

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