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Chem questions.

  1. Jun 16, 2005 #1
    Just having trouble again with a few questions.

    1.Calcium oxide (lime) is a white crystalline solid with a melting point of
    2572c. It is manufactured by heating limestone, coral, sea shells or
    chalk, which are mainly CaCO3, to drive off carbon dioxide, according to
    the following reaction.

    CaCO3(s) --> CaO(S) + CO2(g) Kp= 1.16 atm at 800c

    If 20.0g of CaCO3 were sealed in a 10.0L container and heated to 800c, what
    percentage of CaCO3 would remain unreacted at equilibrium?

    2.A saturated solution of iodine in water contains 0.330g I2 per litre, but
    more than this amount can dissolve in a potassium iodide solution because
    of the following equilibrium.

    I-(aq) + I2(aq) <--> I3- (aq)

    A 0.100 M KI solution dissolves 12.5g of I2 per litre, most of which is
    converted to I3-(aq). Assuming that the concentration of I2(aq) in all
    saturated solutions is the same, calculate the equilibrium constant for
    the above reaction.

    I know Kc= [I3-]/[I-][I2], but I don't know where to go from there.

    3. What is the longest wavelength of light that the ground state C2+ ion will
    absorb? For this question, an MO diagram is given with energy in electron volts. I'm assuming you need to convert the energy in to joules (multiply by 1.602*10^-19) and use E=hc/lambda, but I don't know where to measure the energy from.

    Any help would be great.
  2. jcsd
  3. Jun 16, 2005 #2


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    Staff Emeritus
    Science Advisor

    How many moles of CO2 would produce 1.16 atm at 800°C in 10L, ignoring the volume of 20 g of CaCO3?
  4. Jun 17, 2005 #3
    Ok, I get it. Thanks.
  5. Jun 17, 2005 #4
    Does anyone know how to do questions 2 and 3 (particularly 2)?
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