Physics Help!!! How many atoms of hydrogen are in 250g?

2 Answers

• Find molecular weight of H2O2: 2(1.01) + 2(16.0) = 34.02 g/mole

  Find number of moles in 250 g: (250 g)(1 mole/34.02 g) = 7.3486 moles

  Number of hydrogen atoms = (2)(7.3486 moles) = 14.6972 moles H atoms

  Number atoms = (14.6972 moles)(6.022 x 10^23 atoms/mole) = 8.851 x 10^24 atoms

• H = 1.0079 g /mol

  O = 15.999 g/mol

  so you figure out what one mol of H2O2 would be

  2*1.0079 + 2*15.999 = 34.0138 /mol

  that means 34.0138 grams is 6.023*10^23 molecules

  so 250g/34.0138 = 7.35 mol's

  so the number of molecules

  = 6.023*10^23 * 7.35

  = 4426905000000000000000000

  = 4.427 *10^24 molecules of hydrogen peroxide

  since 2 atoms of H per molecule times by 2

  number of atoms of H in 250 grams H2O2 is

  n = 8.854*10^24

  6.023*10^23 is avogadros number that is the number of atoms of a gas in 22.4 L of gas at Standard temperature and pressure.

  also

  http://en.wikipedia.org/wiki/Avogadro_constant

  good luck hope that helps