Calculate the molality of CsCl in a 19% by
mass aqueous solution.
To calculate the molality of CsCl in a 19% by mass aqueous solution, we need to determine the amount of CsCl in moles and the amount of water in kilograms.
1. Start by assuming we have 100 grams of the solution since the percentage is given by mass.
- This means we have 19 grams of CsCl and 81 grams of water.
2. Convert the amount of CsCl from grams to moles.
- First, find the molar mass of CsCl. The atomic mass of Cs (Cesium) is 132.91 g/mol and that of Cl (Chlorine) is 35.45 g/mol.
- The molar mass of CsCl is 132.91 g/mol + 35.45 g/mol = 168.36 g/mol.
- To convert grams to moles, divide the mass of CsCl by the molar mass: 19 g / 168.36 g/mol = 0.113 moles.
3. Calculate the molality.
- Molality is defined as the number of moles of the solute (CsCl) divided by the mass of the solvent (water) in kilograms.
- The mass of water is 81 grams, which is equivalent to 0.081 kilograms.
- Molality = moles of CsCl / mass of water in kg = 0.113 moles / 0.081 kg ≈ 1.395 mol/kg.
The molality of CsCl in a 19% by mass aqueous solution is approximately 1.395 mol/kg.
To calculate the molality of CsCl in a 19% by mass aqueous solution, we need to know the molar mass of CsCl and the density of the solution.
The molar mass of CsCl is the sum of the atomic masses of cesium (Cs) and chlorine (Cl). According to the periodic table, the atomic mass of Cs is 132.91 g/mol and the atomic mass of Cl is 35.45 g/mol. Therefore, the molar mass of CsCl is:
Molar mass of CsCl = (132.91 g/mol) + (35.45 g/mol) = 168.36 g/mol
Next, we need to determine the amount of CsCl present in the solution. A 19% by mass aqueous solution means that 19 g of CsCl is dissolved in 100 g of the solution (including both CsCl and water).
The mass of CsCl in the solution can be calculated as follows:
Mass of CsCl = (19% of 100 g) = 19 g
Finally, we need to determine the mass of water in the solution. This can be obtained by subtracting the mass of CsCl from the total mass of the solution:
Mass of water = (100 g - 19 g) = 81 g
Now, we can calculate the molality using the formula:
Molality (m) = moles of solute / mass of solvent (in kg)
First, let's calculate the moles of CsCl:
Moles of CsCl = Mass of CsCl / Molar mass of CsCl
= 19 g / 168.36 g/mol
≈ 0.113 moles
Since the mass of the solvent is given in grams, we need to convert it to kilograms:
Mass of water (in kg) = Mass of water / 1000
= 81 g / 1000
= 0.081 kg
Finally, we can calculate the molality:
Molality (m) = 0.113 moles / 0.081 kg
≈ 1.395 mol/kg
Therefore, the molality of CsCl in a 19% by mass aqueous solution is approximately 1.395 mol/kg.
19% w/w CsCl means 19 g CsCl in a soln of 19 g CsCl + 81g H2O.
m = mols/kg solvent. Convert 19 g CsCl to mols and divide by 0.081.