a solution is made by dissolving 25 g NaCl in enough water to make 1.0 L solution. Assume that density of the solution is 1.0 g/mL. calculate the mass percent, molarity, molality, and mole fraction of NaCl.
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To find the mass percent, molarity, molality, and mole fraction of NaCl in the solution, we can follow these steps:
1. Calculate the mass percent:
Mass percent = (Mass of NaCl / Mass of Solution) × 100
Given that the mass of NaCl is 25 grams, and the density of the solution is 1.0 g/mL, we can find the mass of the solution.
Mass of Solution = Volume of Solution × Density of Solution
Volume of Solution = 1.0 L = 1000 mL
Now, calculate the mass of the solution:
Mass of Solution = 1000 mL × 1.0 g/mL = 1000 grams
Calculate the mass percent:
Mass percent = (25 grams / 1000 grams) × 100 = 2.5%
2. Calculate the molarity:
Molarity (M) = (Amount of Substance / Volume of Solution) in liters
The amount of substance is given in moles. To calculate the moles of NaCl, we need to know its molar mass. The molar mass of NaCl is:
Molar mass of NaCl = atomic mass of Na + atomic mass of Cl
= 22.99 g/mol + 35.45 g/mol
= 58.44 g/mol
Moles of NaCl = Mass of NaCl / Molar mass of NaCl
= 25 grams / 58.44 g/mol
Now, calculate the molarity:
Molarity = (25 grams / 58.44 g/mol) / 1.0 L = 0.427 M
3. Calculate the molality:
Molality (m) = (Amount of Substance / Mass of Solvent) in kg
The mass of solvent can be obtained by subtracting the mass of NaCl from the mass of the solution.
Mass of Solvent = Mass of Solution - Mass of NaCl
= 1000 grams - 25 grams
Now, calculate the molality:
Molality = (25 grams / (1000 grams - 25 grams)) / 1.0 kg
4. Calculate the mole fraction:
The mole fraction of NaCl is the ratio of the moles of NaCl to the total moles in the solution.
Moles of Water = (Mass of Solution - Mass of NaCl) / Molar mass of water
= (1000 grams - 25 grams) / 18.015 g/mol
Mole fraction = Moles of NaCl / (Moles of NaCl + Moles of Water)
Now, you can substitute the given values into these equations to find the mass percent, molarity, molality, and mole fraction of NaCl in the solution.