The density of 3M solution of NaCl is 1.25 g/mL. Calculate the molality of the soution.
3 M solution means 3 moles solute/L soln.
The soln density is 1.25 g/mL; therefore, 1000 mL soln x 1.25 g/L = 1250 grams for the soln. Part of the 1250 g is water, part NaCl. Since it is 3 moles, that is 3 moles x 58.44 g/mol =175.33 g NaCl. Thus the water portion is 1250-175.33 = ??
Then 3 moles/kg solvent = m
suppose you mix 15 g of Na2SO4 and 7.5g of C.Which is the limiting reaction
To calculate the molality of a solution, we need to know the moles of solute (NaCl) and the mass of the solvent (water).
1. Convert the given density of the solution (1.25 g/mL) to mass by using the density formula: mass = density x volume.
Let's assume we have 1 L (1000 mL) of the solution, so the mass of the solution is 1.25 g/mL x 1000 mL = 1250 g.
2. Determine the moles of NaCl present in the solution.
Since it's a 3M solution, it means we have 3 moles of NaCl in 1 liter of the solution. So, we have 3 moles of NaCl in 1250 g of the solution.
3. Calculate the mole fraction of NaCl.
To do this, we need to determine the molar mass of NaCl, which is 22.99 g/mol for Na + 35.45 g/mol for Cl.
The molar mass of NaCl is 22.99 g/mol + 35.45 g/mol = 58.44 g/mol.
4. Now, we can calculate the moles of NaCl.
Moles of NaCl = (mass of NaCl) / (molar mass of NaCl) = 1250 g / 58.44 g/mol = 21.41 mol.
5. Finally, calculate the molality of the solution.
Molality (m) is defined as moles of solute per kilogram of solvent.
Since water is the solvent, we need to find the mass of water using the mass of the solution (1250 g) and the mass of NaCl (21.41 mol x 58.44 g/mol = 1250 g).
The mass of water is 1250 g - 1250 g = 0 g (assuming no change in mass during the dissolution process).
Therefore, the molality (m) of the solution is 21.41 mol / 0 kg, which is undefined or infinite.
Please note that the molality is undefined since the mass of water is 0 g. Typically, molality is used for solutes dissolved in a solvent, and for pure solvents, the molality value should be 0.
To calculate the molality of a solution, we need to know the moles of solute and the mass of the solvent.
Given:
Density of 3M solution of NaCl = 1.25 g/mL
Step 1: Convert the density to the mass of the solution
Since the density is given in grams per milliliter, we can assume that 1 mL of the solution has a mass of 1.25 grams.
Step 2: Calculate the moles of solute (NaCl):
A 3M solution means that there are 3 moles of solute (NaCl) for every 1 liter (1000 mL) of the solution.
To convert from moles to grams, we use the molar mass of NaCl, which is:
Na: 22.99 g/mol
Cl: 35.45 g/mol
Molar mass of NaCl = 22.99 + 35.45 = 58.44 g/mol
Using the molar mass, we can calculate the moles of NaCl in 1 liter or 1000 mL of the solution:
3 mol/L x 1000 mL/L = 3000 mol/mL
Step 3: Calculate the mass of the solvent (water):
To find the mass of the solvent (water), we need to subtract the mass of the solute (NaCl) from the mass of the solution.
From step 1, we know that the mass of 1 mL of the solution is 1.25 grams. So, for 1000 mL of the solution, the mass is:
1.25 g/mL x 1000 mL = 1250 grams
Then, to find the mass of the solvent (water), we subtract the mass of the solute:
Mass of solvent (water) = Mass of solution - Mass of solute
= 1250 g - 3000 g
=-1750 g
Note: The negative sign indicates that the mass of the solvent is less than the mass of the solute, which is expected when making a concentrated solution.
Step 4: Calculate the molality (m) of the solution:
Molality (m) is defined as the moles of solute (NaCl) per kilogram of solvent (water).
To convert the mass of the solvent to kilograms:
Mass of solvent (water) = -1750 g = -1.75 kg
Now we can calculate the molality (m) using the formula:
Molality (m) = Moles of solute / Mass of solvent (in kg)
Molality (m) = 3000 mol / 1.75 kg
Molality (m) ≈ 1714.29 mol/kg
Therefore, the molality of the 3M solution of NaCl is approximately 1714.29 mol/kg.