Question #836da

1 Answer
Jan 30, 2016

The mass of Br_2Br2 required to react with 0.9 mol of chalcone is
143.8 g.

Explanation:

First you want to create a chemical equation:

C_15H_12O + Br_2 -> C_15H_11BrO + HBrC15H12O+Br2C15H11BrO+HBr

From this equation we can tell that this reaction is a double replacement reaction. This is because the bromide is more reactive than the hydrogen, and replaces the hydrogen on the benzene ring of the chalcone.

We a given 0.9 mol of C_15H_12OC15H12O, which has a molar mass of 208.26 g/mol.

As the coeficients (the numbers in front of the compounds in the chemical equation) are the same, the 0.9 mol is applicable to use throughout the entire equation.

So, Br_2Br2 has 0.9 mols

n n = m/MmM, which mm = Mass (in grams), MM = Molar mass and nn = Mols
This equation can be reformed to mm = n*MnM

Bromine has a molar mass of 79.9 mol/g. But this is one atom and must be doubled to be the molar mass of Br_2Br2

mm = 0.9*159.80.9159.8
mm = 143.8

Therefore the mass of Br_2Br2 required to react with 0.9 mol of chalcone is 143.8 g.