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17. How many moles are there in a sample containing 1000 molecules of H2O?18. If you wanted a sample of H2O containing 6 x 23molecules, how could you measapproximate number without counting?

17 How many moles are there in a sample containing 1000 molecules of H2O18 If you wanted a sample of H2O containing 6 x 23molecules how could you measapproximat class=

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JoshEast
17) mol of [tex]H_{2}O[/tex] = [tex] \frac{no. of molecule}{L} [/tex]
                            = [tex] \frac{1000 molecules}{6.03 * 10^{23} molecules/mol } [/tex]
                            = 1.658  *   [tex]10^{-21} mol [/tex]

18) mol = [tex] \frac{molecule}{L} [/tex]
      [tex] \frac{Mass}{Mr} = \frac{Molecule}{L} [/tex]
      Let mass of oxygen = x
      [tex] \frac{x}{(2 * 1) + (16)} = \frac{6 * 10^{23} }{6.03 * 10^{23} } [/tex]
      [tex]x = (6 * 10^{23} ) (18 g/ mol)[/tex]
             =  17.9 g

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