An aqueous solution is made by dissolving 23.9 grams of cobalt(II) bromide in 405 grams of water.
The molality of cobalt(II) bromide in the solution is___m.
mols CoBr2 = grams/molar mass = ?
Then m - mols/kg solvent.
To calculate the molality of a solute in a solution, you need to know the number of moles of the solute and the mass of the solvent. Here's how you can find the molality:
Step 1: Calculate the number of moles of cobalt(II) bromide.
To find the number of moles of cobalt(II) bromide, you need to use its molar mass. The molar mass of cobalt(II) bromide (CoBr2) can be calculated by adding the atomic masses of cobalt (Co) and bromine (Br).
The atomic mass of cobalt (Co) is 58.93 g/mol, and the atomic mass of bromine (Br) is 79.90 g/mol.
So, the molar mass of cobalt(II) bromide (CoBr2) = (58.93 g/mol) + 2(79.90 g/mol) = 218.73 g/mol.
To find the number of moles of cobalt(II) bromide, divide the mass of cobalt(II) bromide (23.9 g) by its molar mass:
Number of moles of CoBr2 = 23.9 g / 218.73 g/mol = 0.1095 mol.
Step 2: Calculate the mass of the solvent (water).
The mass of the solvent (water) is given as 405 grams.
Step 3: Calculate the molality.
Molality (m) is defined as the moles of solute per kilogram of solvent. Since the given mass of water is in grams, convert it to kilograms by dividing by 1000.
Mass of water in kg = 405 g / 1000 = 0.405 kg.
Molality (m) = moles of solute (cobalt(II) bromide) / mass of solvent (water in kg)
Molality (m) = 0.1095 mol / 0.405 kg = 0.270 m.
Therefore, the molality of cobalt(II) bromide in the solution is 0.270 m.