An aqueous solution is 25 % mass % NaCI. The density of the solution is 1.05g/ml. What is the molarity of the solution?
25% w/w means 25 g NaCl/100 g soln.
Change 25 g to moles. moles = grams/molar mass.
Use mass = volume x density to determine the volume of the 100 g soln.
Then M = moles/L
Dr Bob, could you please tell me if this is right. Thanks again.
Molar Mass of Na = 22.990
Cl = 35.453
NaCl = 58.453 g/mol
Change g to moles…….
moles= grams/molar mass = (25g) / 58.453 g/mol = 0.427moles
Then M = moles/L
= .427 moles/ 0.0105
= 406.66
To find the molarity of the solution, we need to first determine the concentration of NaCl in moles per liter (Molarity).
Given:
- The solution is 25% mass % NaCl, which means that for every 100 grams of the solution, we have 25 grams of NaCl.
- The density of the solution is 1.05 g/ml.
To calculate the molarity, we need to find the number of moles of NaCl and the volume of the solution in liters.
Step 1: Calculate the mass of NaCl in the solution:
If the solution is 25% mass % NaCl, then for every 100 grams of the solution, we have 25 grams of NaCl.
Let's assume we have 100 grams of the solution.
Mass of NaCl = 25% x 100g = 25g
Step 2: Calculate the volume of the solution:
We know the density of the solution is 1.05 g/ml.
To calculate the volume, we need to divide the mass of the solution (100g) by the density (1.05 g/ml).
Volume of the solution = mass of the solution / density = 100g / 1.05 g/ml = 95.24 ml
Step 3: Convert the volume to liters:
Since the molarity is defined as moles per liter, we need to convert the volume from milliliters to liters.
1 liter = 1000 ml
Volume of the solution in liters = Volume of the solution / 1000 = 95.24 ml / 1000 = 0.09524 L
Step 4: Calculate the molarity:
Molarity (M) is defined as moles of solute divided by the volume of the solution in liters.
Molarity = Moles of NaCl / Volume of the solution in liters
To find the number of moles, we need to use the molar mass of NaCl.
The molar mass of NaCl = atomic mass of Na + atomic mass of Cl
= 22.99 g/mol + 35.45 g/mol
= 58.44 g/mol
Now we can find the moles of NaCl:
Moles of NaCl = Mass of NaCl / Molar mass of NaCl
= 25g / 58.44 g/mol
= 0.428 mol
Finally, we can calculate the molarity:
Molarity = Moles of NaCl / Volume of the solution in liters
= 0.428 mol / 0.09524 L
= 4.494 M
Therefore, the molarity of the solution is approximately 4.494 M.