2.34 x 10^23
Calculate the molar mass of CH2Br2
Atomic weight carbon = 12.0107
Atomic weight hydrogen = 1.00794
Atomic weight Bromine = 79.904
Molar mass of CH2Br2 = 12.0107 + 2 * 1.00794 + 2 * 79.904 = 173.83458
Now divide the given mass of CH2Br2 you have by the molar mass
33.8 g / 173.83458 g/mol = 0.194438 moles
Since each molecule of CH2Br2 has 2 bromine atoms, multiply by 2
0.194438 * 2 = 0.388876 moles
Finally, multiply by avogadro's number
0.388876 * 6.0221409 x 10^23 = 2.341866 x 10^23
Since you only have 3 significant figures, round the result to 3 significant figures.
2.341866 x 10^23 = 2.34 x 10^23
