The density of 3M solution of Nacl is 1.25g ml^-1. Calculate the molality of the solution?

Question

Answer

Answer

Molarity 3M means 3 moles of NaCl are in 1000ml or 1 L water

molality means no. of moles of solute present per kg of solvent

density of solution is 1.25 g/ml

=>wt of solution is 1.25 �1000 = 1250 gm

wt of NaCl is 3�58.5 = 175.5

wt of solvent = 1250-205.5= 1074.5gm= 1.0445kg

molality = 3/1.0745 = 2.791m

Answer

Answer

Answer

Density = 1.25 g ml^-1 ( Given )
mass = Density × Volume
mass = 1.25 × 1000
mass = 1250.00 = 1250 g ( weight of solution )

Molecular mass of NaCl = 23 + 35.5 = 58.5 g

Weight of NaCl = n × Mm = 3 × 58.5 = 175.5 g

Weight of solvent = 1250 - 175.5
= 1074 . 5 g

Molality = No. of moles of solute / Mass of solvent in kg

Molality = 3 / 1074. 5

So , Molality = 2. 791 ( approx) .

Hope, this will help you .

Answer

Answer

Calculation of Molality of 3M Solution of NaCl

Step 1: Determine the Molar Mass of NaCl
- The molar mass of NaCl is 58.44 g/mol (22.99 g/mol for Na + 35.45 g/mol for Cl)

Step 2: Calculate the Mass of NaCl in 1 L of 3M Solution
- The molarity of the solution is 3M, which means there are 3 moles of NaCl in 1 liter of solution.
- The mass of 3 moles of NaCl can be calculated using the molar mass of NaCl: 3 mol x 58.44 g/mol = 175.32 g.
- Therefore, there are 175.32 g of NaCl in 1 liter of 3M solution.

Step 3: Convert the Volume of Solution to Mass of Solvent
- To calculate molality, we need to know the mass of the solvent (water) in the solution.
- The density of the solution is 1.25 g/mL, which means that 1 liter of solution has a mass of 1.25 kg (1000 mL x 1.25 g/mL = 1250 g = 1.25 kg).
- Therefore, the mass of water in 1 liter of 3M NaCl solution is: 1.25 kg - 0.17532 kg = 1.07468 kg.

Step 4: Calculate Molality
- Molality is defined as the number of moles of solute per kilogram of solvent.
- The number of moles of NaCl in 1 liter of 3M solution is 3 moles.
- The mass of water in 1 liter of 3M solution is 1.07468 kg.
- Therefore, the molality of the solution is: (3 mol) / (1.07468 kg) = 2.79 mol/kg (rounded to two decimal places).

Therefore, the molality of the 3M solution of NaCl is 2.79 mol/kg.

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