Answer:
C.) 76.1 grams
Explanation:
To find the mass of bromine, you need to (1) convert grams AlCl₃ to moles AlCl₃ (via molar mass), then (2) convert moles AlCl₃ to moles Br₂ (via mole-to-mole ratio from reaction coefficients), and then (3) convert moles Br₂ to grams Br₂ (via molar mass). It is important to arrange your ratios/conversions in a way that allows for the cancellation of units (the desired unit should be in the numerator).
Molar Mass (AlCl₃): 26.982 g/mol + 3(35.453 g/mol)
Molar Mass (AlCl₃): 133.332 g/mol
2 AlCl₃ + 3 Br₂ --> 2 AlBr₃ + 3 Cl₂
Molar Mass (Br₂): 2(79.904 g/mol)
Molar Mass (Br₂): 159.808 g/mol
42.3 g AlCl₃ 1 mole 3 moles Br₂ 159.808 g
------------------ x ----------------- x ---------------------- x ------------------- =
133.332 g 2 moles AlCl₃ 1 mole
= 76.0 g Br₂
*Our answers are slightly different most likely because we used slightly different molar masses*
