Homework Help Forum: chemistry

Posted by Cheimie on Thursday, November 5, 2009 at 1:51am.

Hello, ((((((I need the answer in a hour from my posting))))) I have been posting this problme for four days ago, so please show Sympathy. I solved it but I want to be 100% su ...there is moreshow problem Hello, ((((((I need the answer in a hour from my posting))))) I have been posting this problme for four days ago, so please show Sympathy. I solved it but I want to be 100% sure to go on. The result of Silicon crystal analyzation shown that there is an amount of arsenic As atoms in silicon crystal at Concentrate percentage which is 0.0002%. assuming if conductivity concentration which promote by heat is an eliminated amount. Find out the electrical conducting density? Where Molarity of silicon = 12.1cm3/mole my humble ideas goes like, Density= w/v....1 V= Moles#/Molarity....2 1/Calculation of moles number: Moles#=w/M.wt....3 = .0002*100/28.1 =7.117*10^-4 mole 2/ Calculation of volume: back to equation #2 V=7.117*10^-4/12.1 =5.88*10-5 cm3 If I do it in appropriate way why I couldn't find the Weight in grams of Si. Hold on, silicon is the conductive and arsenic is a blotch which give us a N-type conducting. Avoiding the weight of Si we can go throw this rule which says: Density =the number of conductive * 1 cm3 Where 1 cm3 = 1mole =Avogadro’s number 1 mole = 6.022 x 10^23 atoms Now, how could I figure out the number of conductive? How can I solve this, Am I doing well ?! Draw the diagram of band and name the form of boundary Finding out the Si weight W of Si =moles#/atomic mass = 7.117*10^-4/28.086 = 2.534*10^-5gm Back to density D = 2.534*10^-5/5.88*10^-5 = 0.4309gm/cm3 Another solution segma= 1/D Log segma = 4.247 –(92924/T) =2.7221998*10^-6 ms D = 367.349*10^3 I really need help. Electrical conductivity or specific conductance is a measure of a material's ability to conduct an electric current. When an electrical potential difference is placed across a conductor, its movable charges flow, giving rise to an electric current. The conductivity s is defined as the ratio of the current density J to the electric field strength E J=sE where electrical conductivity s is has been calculated means it can be found in table as a constant. !!!!!!!!! Any Ideas! will I have an answer any time soon?! please respond

• chemistry - DrBob222, Thursday, November 5, 2009 at 11:49am

  Your question(s) and answer(s)(?) are so disorganized that I can't make heads or tails of the question(s), much less how you propose to solve it(them).

  
  

• chemistry - Cheimie, Thursday, November 5, 2009 at 5:51pm

  Thanks dr Bob for your reply. Here's the organized version Question: Result of Silicon crystal analyzation shown that there is an amount of arsenic As atoms in silicon crystal at Concentrate percentage which is 0.0002%. Assuming if conductivity concentration which promote by heat is an eliminated amount. Find out the electrical conducting density? Where Molarity of silicon = 12.1cm3/mole. Answer: We get N-type semiconductor Density= w/v....(1) V= Moles#/Molarity....(2) 1/Calculation of moles number: Moles#=w/M.wt....(3) = .0002*100/28.1 =7.117*10^-4 mole 2/ Calculation of volume: back to equation #2 V=7.117*10^-4/12.1 =5.88*10-5 cm3 3/W of Si =moles#/atomic mass = 7.117*10^-4/28.086 = 2.534*10^-5gm Back to density D = 2.534*10^-5/5.88*10^-5 = 0.4309 gm/cm3 Question: where could the previous answer take me to? Question: Dose electrical conductivity density try to tell me something about which of charge transfers (holes or electrons) have majority on other? Information: I'm already know that it's N-type SC which means the charge transfer is electron. Question: Did I need to find the electron numbers?

  
  

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