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Homework Help: Kinetics of metals reacting with acids

  1. Nov 5, 2006 #1
    hey. im doing an investigation into reactions of acids with Mg. Firstly, iv investigated how order with respect to the acid varies for different acids
    i found that the orders for each of the acids are:

    Hydrochloric acid: 2
    Sulphuric acid: 1
    Phosphoric acid: 1.8

    in an article, it said that: the effect of added sodium and magnesium chlorides indicated that high concentrations of added salt slow down the reaction considerably. There is other evidence that small concentrations of added sodium chloride increase the rate of reaction, and it is well known that sodium chloride solution alone is highly corrosive to magnesium, far more so than solutions of nitrates or sulphates.

    how would i find out the order of the reaction with respect to Cl- ions?? someone said they did it and they got a negative order, which would make comply with what was said above.

    for the orders experiment i just used a relatively simple pracitcal setup- using a range of acid concs and noting the time it took for a certain mass of Mg to disappear. Plotting log rate (=log 1/time) vs log conc acid, i determined the order by the gradient of the graph. Unfortunately, i cant think of a similar way to determine how the order of Cl- ions or SO42- ions using a similar method. thanks for any help

    (apparently, i was told that by applying thermodynamics to this problem, i would be able to find out whether the reaction is SN1 or SN2...but i can't figure that one out either. any suggestions please?)

    i no that iv written quite a bit and would appreciate any help.

    Last edited: Nov 5, 2006
  2. jcsd
  3. Nov 5, 2006 #2
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