Question

Calculate the molality of each of the following aqueous solution:

2.50M NaCl solution ( density of solution =1.08g/mol)
48.2 % mass KBr solution

Answer 1

[AI-generated answer — Bot GPT 3.5]

First, we need to calculate the molality of the 2.50M NaCl solution:

Step 1: Calculate the molar mass of NaCl
Na: 22.99 g/mol
Cl: 35.45 g/mol
Molar mass of NaCl = 22.99 g/mol + 35.45 g/mol = 58.44 g/mol

Step 2: Calculate the molality using the formula
Molality = moles of solute / mass of solvent in kg
Since the molarity is 2.50M, the moles of NaCl in 1L of solution:
2.50 moles/L * 1 L = 2.50 moles

The mass of 1L of solution can be calculated using the density given:
Mass = volume * density = 1 L * 1.08 g/mL = 1.08 kg

Now, calculate the molality:
Molality = 2.50 moles / 1.08 kg = 2.31 mol/kg

Therefore, the molality of the 2.50M NaCl solution is 2.31 mol/kg.

Next, we need to calculate the molality of the 48.2% mass KBr solution:

Step 1: Assume we have 100g of the 48.2% mass KBr solution, therefore, mass of KBr = 48.2g

Step 2: Calculate the molar mass of KBr
K: 39.10 g/mol
Br: 79.90 g/mol
Molar mass of KBr = 39.10 g/mol + 79.90 g/mol = 119 g/mol

Step 3: Calculate the moles of KBr in 100g of solution:
Moles of KBr = mass / molar mass = 48.2g / 119 g/mol = 0.405 moles

Step 4: Calculate the molality using the formula
Molality = moles of solute / mass of solvent in kg
Since we have 100g of solution, the mass of solvent is:
100g - 48.2g = 51.8g = 0.0518 kg

Now, calculate the molality:
Molality = 0.405 moles / 0.0518 kg = 7.81 mol/kg

Therefore, the molality of the 48.2% mass KBr solution is 7.81 mol/kg.