Calculate the molarity and molality of 37.0%(w/w) HCI with a density of
1.19 g mL-1.The molecular mass of HCI is 36.46 g mol-1.
M = mols/L, then
1.19 g/mL x 1000 mL x 0.37 x (1 mol/molar mass HCl) = M = approximately 12M
m = mols/kg solvent.
How many grams of the solution do you have above? You know that's
1.19 x 1000 = g soln.
How many grams HCl are there?
That's g soln x 0.37
How many grams water (solvent) are there?
That's g solution - g HCl = g solvent.
Change to kg solent and
m = mols HCl/kg solvent. I think it's something like 15 or 16 m.
I forgot to add to the explanation that when calculating everything, all units for volume should be converted from mL to L, and the units for mass, when calculating molality, should be converted from g to Kg.
37.0% =37.0g/100g of mixture. 37g/36.46g mol-1 will give you the number of moles in your solution. Since 63% =63g of the remaining mixture, use the density and solve for the volume (63g/1.19g mL-1). Take the answer that you get for moles and the answer you get for volume and calculate the molarity (moles/volume). To calculate the molality, take the answer that you get for moles and divide it by the weight of solvent (moles/63g). I am a little rusty at performing chemistry calculations, so hopefully someone else comes along and verifies this or gives you the correct way of solving the problem. But I believe this is correct.
Also, grams of the solution shouldn't be 63g but 100g.
To calculate the molarity and molality of the solution, we need to follow a few steps:
Step 1: Convert the given percent by mass (%w/w) to grams.
Given that the solution is 37.0%(w/w), this means that there are 37.0 grams of hydrochloric acid (HCl) in every 100 grams of the solution. Let's calculate the mass of HCl in the solution:
Mass of HCl = (37.0 g / 100 g) × Total mass of the solution
Assuming the total mass of the solution is 1000 grams (1 L), the mass of HCl can be calculated as:
Mass of HCl = (37.0 g / 100 g) × 1000 g = 370 g
Step 2: Calculate the number of moles of HCl using its molecular mass.
The molecular mass of HCl is given as 36.46 g/mol. We can use this to calculate the number of moles:
Number of moles of HCl = Mass of HCl / Molecular mass of HCl
Number of moles of HCl = 370 g / 36.46 g/mol ≈ 10.13 mol
Step 3: Calculate the molarity of the solution.
Molarity, denoted as M, is defined as the number of moles of solute (in this case, HCl) per liter of solution. Since the total volume of the solution is not given, we can assume it to be 1 L for simplicity.
Molarity (M) = Number of moles of solute / Volume of solution (in liters)
Molarity (M) = 10.13 mol / 1 L = 10.13 M
Therefore, the molarity of the 37.0%(w/w) HCl solution is approximately 10.13 M.
Step 4: Calculate the molality of the solution.
Molality, denoted as m, is defined as the number of moles of solute (HCl) per kilogram of solvent (water). To calculate the molality, we need to consider the density of the solution.
First, we need to calculate the mass of water in the solution:
Mass of water = Total mass of the solution - Mass of HCl
Mass of water = 1000 g - 370 g = 630 g
Next, we convert the mass of water to kilograms:
Mass of water = 630 g / 1000 = 0.63 kg
Now we can calculate the molality:
Molality (m) = Number of moles of solute / Mass of solvent (in kilograms)
Molality (m) = 10.13 mol / 0.63 kg ≈ 16.08 m
Therefore, the molality of the 37.0%(w/w) HCl solution is approximately 16.08 m.