assuming that sea water hos 3.5 weight percent in aqueous solution of NaCl what is molality
molality = m = mols solute/kg solvent
a 3.5 wt% NaCl is 3.5 g NaCl/100 g solution and that is
3.5 g NaCl/(3.5 g NaCl + 96.5 g H2O) So if we take a 1000 g sample it will contain 35 g NaCl in 965 g H2O.
m = mols NaCl/kg solvent.
mols NaCl = g NaCl/molar mass NaCl = 35/58.5 = ?
kg solvent = 0.965
Solve for m = ?
To calculate the molality of a solution, we need to use the formula:
Molality (m) = moles of solute / mass of solvent in kg
In this case, the solute is NaCl (sodium chloride), and the solvent is water.
Given that sea water has a weight percent of 3.5% NaCl, it means that for every 100 grams of sea water, 3.5 grams are NaCl.
Now, we need to convert the weight of NaCl to moles. The molar mass of NaCl is 58.44 g/mol, which means that 1 mole of NaCl weighs 58.44 grams.
To calculate the moles of NaCl, we can use the formula:
moles of NaCl = weight of NaCl / molar mass of NaCl
moles of NaCl = 3.5 g / 58.44 g/mol
moles of NaCl ≈ 0.060 moles
Now, let's determine the mass of the solvent (water). Since we're assuming pure water, the mass of water is equal to the mass of the sea water.
Finally, we need to convert the mass of water into kilograms, as the molality is expressed in moles of solute per kilogram of solvent.
Let's assume we have 1000 grams of sea water (1 kg):
mass of solvent (water) = 1000 g
converting the mass of solvent to kg:
mass of solvent (water) = 1000 g / 1000 = 1 kg
Now, we can calculate the molality:
Molality (m) = moles of solute / mass of solvent in kg
Molality (m) = 0.060 moles / 1 kg
Molality (m) ≈ 0.060 m
Therefore, the molality of the sea water with 3.5% NaCl is approximately 0.060 m.
To find the molality of a solution, you need to know the amount of solute (in moles) divided by the mass of the solvent (in kilograms).
Given that sea water has a weight percent concentration of 3.5% NaCl, we can assume that 3.5 grams of NaCl is present in every 100 grams of solution.
To calculate the molality, we need to convert these values to moles and kilograms.
1. Determine the molar mass of NaCl (sodium chloride). The molar mass of Na is 22.99 g/mol, and the molar mass of Cl is 35.45 g/mol. Adding these values together gives us:
Molar mass of NaCl = 22.99 g/mol + 35.45 g/mol = 58.44 g/mol
2. Calculate the moles of NaCl in the given mass. We have 3.5 grams of NaCl, so we can divide this by the molar mass to find moles:
Moles of NaCl = 3.5 g / 58.44 g/mol = 0.0599 mol
3. Determine the mass of the water solvent. Since we're assuming sea water, we can assume that the amount of water is much greater than the NaCl, and we can disregard the mass contribution of NaCl. Let's say we have 100 grams of sea water.
4. Convert the mass of water to kilograms:
Mass of water = 100 g = 0.1 kg
5. Finally, calculate the molality by dividing the moles of NaCl by the mass of water in kilograms:
Molality = 0.0599 mol / 0.1 kg = 0.599 mol/kg (rounded to three decimal places)
Therefore, the molality of the sea water solution with 3.5% weight percent NaCl is approximately 0.599 mol/kg.