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    Someone Ask me AP Chem Questions

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    Ahmed
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    Someone Ask me AP Chem Questions

    Post by Ahmed on Fri May 07, 2010 8:09 pm

    Ehm...Lev Very Happy

    Also anyone can ask me Chem questions. Im a chemist after all Razz


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    Re: Someone Ask me AP Chem Questions

    Post by The Banker on Fri May 07, 2010 8:14 pm

    deduce the oxidation number of iodine in::
    a) I2O7
    b) IO3-
    c) KIO4
    d) Ba(IO2)2

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    Re: Someone Ask me AP Chem Questions

    Post by Ahmed on Fri May 07, 2010 8:16 pm

    a)+7
    b)+5
    c)+7
    d)+3

    Harder please.


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    Re: Someone Ask me AP Chem Questions

    Post by Fifi on Fri May 07, 2010 8:20 pm

    eww i hate finding oxidation numbers


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    Re: Someone Ask me AP Chem Questions

    Post by The Banker on Fri May 07, 2010 8:28 pm

    Methan can be trapped in water as solid methane hydrate, [CH4(H2O)6]. The reaction between methane gas and water to form methane hydrate is exothermic:
    CH4(g) + 6H2O(l)<---> [CH4(H2O)6](s)
    Huge quantities of methane hydrate are found at the bottom of the sea off the Canadian coast, where the pressure is very high.

    a) Predict what would happen if the pressure on solid methane hydrate were predicted at 1 atm

    b) Predict what would happen to methane hydrate if it were heated.

    c) Predict what would happen if the methane hydrate crystals were brought to the surface of the sea, from the great depth of the Canadian coast.

    ======
    <---> is my version of a reversible reaction by da way Wink
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    Re: Someone Ask me AP Chem Questions

    Post by Ahmed on Fri May 07, 2010 8:34 pm

    1-What do you mean by "...were predicted"?
    2-It would become an anhydrate.
    3-It would become gas


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    Re: Someone Ask me AP Chem Questions

    Post by The Banker on Fri May 07, 2010 8:35 pm

    soz "were reduced"
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    Re: Someone Ask me AP Chem Questions

    Post by Ahmed on Fri May 07, 2010 8:37 pm

    Did I get 2 and 3 right?

    1-It would become a gas


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    Re: Someone Ask me AP Chem Questions

    Post by The Banker on Fri May 07, 2010 8:39 pm

    ahmed, ur forgetting its a reversible reaction.. u gotta talk about equilibrium for a,b and c

    have another shot at it..
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    Re: Someone Ask me AP Chem Questions

    Post by Ahmed on Fri May 07, 2010 8:40 pm

    I know it's at equib. That's why is aid it will become a gas (and water). If it wasn't at equib. it couldn't go back to being a gas.


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    Re: Someone Ask me AP Chem Questions

    Post by The Banker on Fri May 07, 2010 8:50 pm

    kay..
    a) There is 1 mol of gas on the left hand side of the equation and none on the right. By Le Chatelier's principal a decrease in pressure will cause the equilibrium to shift to the side with more gas molecules. This means that the methane hydrate will decompose and methane gas will be produced.

    - so u get the mark for this Q... more detail would have been nice tho Razz

    b)The reaction written is exothermic. An increase in temperature will cause the equilibrium position to shift to the endothermic direction, therefore methane hydrate will be produced

    - again u get the mark.. but u need detail in ur answer man

    c)Raising the solid methane hydrate from the cold ocean floor means a decrease in pressure and an increase in temperature. This will result in methane hydrate decomposing into methane and water

    - don't think u'll get marks for this one...
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    Re: Someone Ask me AP Chem Questions

    Post by Ahmed on Fri May 07, 2010 8:51 pm

    Yeah...I thought it wasn't neccessary to mention Le Charteir...it was implied.

    Asfor C, I serislouy didn't get the Question then....

    NEXT!


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    Re: Someone Ask me AP Chem Questions

    Post by The Banker on Fri May 07, 2010 8:54 pm

    Explain why sulpher has a higher melting temperature than phosphorus, and why silicon has a much higher melting temperature than both sulpher and phosphorus
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    Re: Someone Ask me AP Chem Questions

    Post by Ahmed on Fri May 07, 2010 8:58 pm

    Silicon has a higher MP than both becasue it is a metaloid.Whil the other two are nonmetals.

    Phosphorous has a higher melting point because it has less nonmetalic character


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    Re: Someone Ask me AP Chem Questions

    Post by The Banker on Fri May 07, 2010 8:59 pm

    whats MP?
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    Re: Someone Ask me AP Chem Questions

    Post by Ahmed on Fri May 07, 2010 8:59 pm

    Melting Point


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    Re: Someone Ask me AP Chem Questions

    Post by The Banker on Fri May 07, 2010 9:06 pm

    Both Sulpher and Phosphorus have simple molecular structures, with instantaneous induced dipole forces between the molecules.
    Sulpher is S8 and so has more electrons in a molecule than does Phosphorus which is P4. This means that the dipole forces between the sulpher molecules are stronger than those between phosphorous molecules. Therefore mole energy is needed to separate them, this results to sulpher having a higher melting temperature than phosphorus.

    Silicon has giant atomic structure with strong covalent bonds between the atoms. These have to be broken for silicon to melt and so a much higher temperature is required
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    Re: Someone Ask me AP Chem Questions

    Post by Ahmed on Fri May 07, 2010 9:08 pm

    Covalent bonds are also between the P and S. You could have also explained that S is greater by london dispersion forces.

    NEXT


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    Re: Someone Ask me AP Chem Questions

    Post by The Banker on Fri May 07, 2010 9:11 pm

    this ain't me answerin by the way.. its George Facer.. THE George Facer Razz
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    Re: Someone Ask me AP Chem Questions

    Post by Ahmed on Fri May 07, 2010 9:13 pm

    I don't know that noob but Im also right Very Happy

    What happened to the next HARD Q...your Qs are waaaaay too easy Marwa :S


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    Re: Someone Ask me AP Chem Questions

    Post by The Banker on Fri May 07, 2010 9:28 pm

    i'm going zzzz now... u can have another Q tomoz Razz
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    Re: Someone Ask me AP Chem Questions

    Post by Ahmed on Fri May 07, 2010 9:29 pm

    Aww, ok good night Wink


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    Re: Someone Ask me AP Chem Questions

    Post by The Banker on Sat May 08, 2010 9:32 am

    A Thermometer is labelled as having an accuracy of "+ or -" 0.2 degrees Celsius.
    In an energy of neutralisation reaction, the temperature before the reaction was 17.4 degrees Celsius and after the reaction was 24.5 degrees Celsius. The mass of the liquid was 100g. The specific heat capacity of the liquid is 4.18 /g C
    Calculate the percentage error used by the thermometer and hence the error in the evaluation of the heat produced.
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    Re: Someone Ask me AP Chem Questions

    Post by Ahmed on Sat May 08, 2010 12:16 pm

    Q=mCT

    Q=(100g)(4.18/g C)(7.1 C)
    Q=2967.8 kJ/mol

    Q=(100g)(4.18 /g C)(7.3 C)
    Q=3051.4 kJ/mol

    Q=(100g)(4.18/g C)(6.9 C)
    Q=2884.2 kJ/mol

    (3051.4-2967.8 )/2967.8=2.82%
    (2884.2-2967.8 )/2967.8=-2.82%

    +/- 2.82%

    Am I right?

    NEXT QUESTION


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    Re: Someone Ask me AP Chem Questions

    Post by The Banker on Sat May 08, 2010 12:56 pm

    have another stab at it...

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