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Homework Help: Electric current help please

  1. Oct 12, 2009 #1
    1. The problem statement, all variables and given/known data
    Find the total electric charge of all the electrons in a 50kg sample of water

    2. Relevant equations
    a conversion factor

    3. The attempt at a solution
    I need the atomic # and the atomic mass but it is water. If I had those two i could solve the problem. How do i get those two things?
  2. jcsd
  3. Oct 12, 2009 #2


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    Homework Helper

    Water is H2O - two oxygen and two hydrogen atoms. You can look up their masses and charges on a periodic table or look up the elements in Wikipedia.
  4. Oct 12, 2009 #3
    The atomic number of an element also tells you have many electrons it has.
    The atomic number of Hydrogen is 1, and that of oxygen is 8.

    The molar mass of water is 18 grams/mol.

    There are [tex]N_A[/tex] molecules in one mol of substance.

    [tex]N_A=6.02*10^{23} mol^{-1}[/tex]
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