A sample of 0, 3220g of an ionic compound containing bromide ions (Br-) is dissolved in water and treated with excess of AgNO3. If the mass of the precipitate
of AgBr formed is 0, 6964g, answer: a) what percentage of bromine in molar mass? b) Give the mass of bromine in the compound formed. c) Which the percentage by mass of bromine in the original compound?
Answered above.
To answer these questions, we need to go through a step-by-step process.
Step 1: Calculate the number of moles of AgBr precipitated.
To find the number of moles of AgBr, we can use its molar mass, which is obtained from the periodic table. The atomic masses are: Ag = 107.87 g/mol and Br = 79.90 g/mol.
Mass of AgBr precipitate = 0.6964 g
Number of moles of AgBr = (mass of AgBr precipitate) / (molar mass of AgBr)
= 0.6964 g / (107.87 g/mol + 79.90 g/mol)
= 0.6964 g / 187.77 g/mol
≈ 0.0037 mol
Step 2: Determine the molar mass of the bromine (Br) in the compound.
The molar mass of bromine, in this case, is the molar mass of Br multiplied by the number of bromine atoms present in one formula unit of the compound.
Given that the compound contains Br- ions, which will combine with Ag+ ions to form AgBr. Since AgBr is a 1:1 ratio compound, the number of bromine atoms in one formula unit is also 1.
Molar mass of bromine = (molar mass of Br) x (number of bromine atoms)
= 79.90 g/mol x 1
= 79.90 g/mol
Step 3: Calculate the mass of bromine in the compound.
To find the mass of bromine in the compound, multiply the number of moles of AgBr precipitated by the molar mass of bromine.
Mass of bromine in the compound = (number of moles of AgBr precipitated) x (molar mass of bromine)
= 0.0037 mol x 79.90 g/mol
≈ 0.296g
Step 4: Calculate the percentage of bromine in the molar mass.
To find the percentage of bromine in the molar mass, divide the molar mass of bromine by the molar mass of the entire compound and multiply by 100%.
Percentage of bromine in molar mass = (molar mass of bromine)/(molar mass of the compound) x 100%
Since we don't have the information about the molar mass of the compound, we cannot calculate the percentage of bromine in the molar mass.
Step 5: Calculate the percentage by mass of bromine in the original compound.
To find the percentage by mass of bromine in the original compound, divide the mass of bromine in the compound by the mass of the original compound and multiply by 100%.
Mass of original compound = mass of AgBr precipitate = 0.6964 g
Percentage by mass of bromine in the original compound = (mass of bromine in the compound)/(mass of original compound) x 100%
= (0.296 g)/(0.6964 g) x 100%
≈ 42.5%
Therefore, the answers are:
a) We cannot determine the percentage of bromine in the molar mass without knowing the molar mass of the compound.
b) The mass of bromine in the compound formed is approximately 0.296g.
c) The percentage by mass of bromine in the original compound is approximately 42.5%.