To determine the number of moles in each substance, we need to divide the mass of the substance by its molar mass.
67.42 g Si:
The molar mass of Si is 28.0855 g/mol (rounded to 4 decimal places). Therefore, the number of moles of Si is:
67.42 g / 28.0855 g/mol = 2.3992 mol (rounded to 4 decimal places).
11.82 g gold:
The molar mass of gold is 196.9665 g/mol (rounded to 4 decimal places). Therefore, the number of moles of gold is:
11.82 g / 196.9665 g/mol = 0.060 mol (rounded to 3 decimal places).
28.8 g Br₂:
The molar mass of Br₂ is 159.808 g/mol (rounded to 3 decimal places). Therefore, the number of moles of Br₂ is:
28.8 g / 159.808 g/mol = 0.1803 mol (rounded to 4 decimal places).
Therefore, the number of moles in each substance is:
2.3992 mol Si
0.060 mol gold
0.1803 mol Br₂.