The material Magnesium Sulfate What mass of dry material would be needed to make an aqueous solution with a molality of 4 moles/kg solution ? What mass of water is needed?
4 (24.305+ 32.065+ (4 x 15.999)) =481.5 ?Not sure where to go from here or if the problem is complete.
Let me point out that your definition of molality is not right. The definition is m = #mols/kg SOLVENT and not kg SOLUTIION. So you have te mols calculated, place that is 1 kg solvent and you have it.
So just divide it. The mass of the dry material is 481.5 g or kg???? I'm sorry I'm still confused about this. The mass of the water is 1 kg right??
OR would the mass of the dry material be 481.5 M since we are dealing with molarity.
You aren't dealing with molarity, you are dealing with molality.
To find the mass of dry magnesium sulfate needed to make an aqueous solution with a molality of 4 moles/kg solution, you would follow these steps:
Step 1: Calculate the molar mass of Magnesium Sulfate (MgSO4):
The molar mass of MgSO4 can be calculated by summing the atomic masses of each element present in the compound. In this case, Magnesium (Mg) has an atomic mass of 24.305 g/mol, Sulfur (S) has an atomic mass of 32.065 g/mol, and Oxygen (O) has an atomic mass of 15.999 g/mol.
Therefore, the molar mass of MgSO4 is:
Mg: 1 × 24.305 g/mol = 24.305 g/mol
S: 1 × 32.065 g/mol = 32.065 g/mol
O: 4 × 15.999 g/mol = 63.996 g/mol
Total molar mass of MgSO4: 24.305 + 32.065 + 63.996 = 121.366 g/mol
Step 2: Calculate the mass of MgSO4 needed for a 4 moles/kg solution:
The molality (m) is defined as the moles of solute per kg of solvent. In this case, the solute is MgSO4.
Given:
Molality (m) = 4 moles/kg
To calculate the mass of MgSO4, we can use the following formula:
Mass of solute (MgSO4) = Molality (m) × Molar mass of MgSO4 × Mass of solvent (in kg)
Mass of solvent (water) would be needed to calculate the mass of MgSO4 needed:
Step 3: Calculate the mass of water (solvent) needed:
Since we have the molality and mass of solute, we can rearrange the formula.
Mass of solvent (water) = Mass of solute (MgSO4) / (Molality (m) × Molar mass of MgSO4)
Let's substitute the given values:
Mass of solvent (water) = Mass of solute (MgSO4) / (4 moles/kg × 121.366 g/mol)
Now, we need to find the mass of the dry material, so we can calculate the final answer:
Step 4: Calculate the mass of dry material (MgSO4):
To find the mass of the dry material, we need to consider that the mass of the solvent (water) is equal to the mass of the solution (solution = solvent + solute). Therefore,
Mass of dry material (MgSO4) = Mass of solution - Mass of solvent (water)
It's important to note that the mass of the solution refers to the final mass, including both the solvent (water) and the solute (MgSO4).
Let's calculate the mass of dry material using the information we have:
Mass of dry material (MgSO4) = Mass of solute (MgSO4) + Mass of solvent (water)
Finally, you need to substitute the known values into the equation and perform the calculations to obtain the mass of dry material required.