A 15.0ml sample of NaCL solution has a mass of 15.78g.after the NaCL solution is evaporated to dryness, the dry salt residue has a mass of 3.26g. calculate the following concentrations for the %(m/m), % (m/v), molarity (M)
The problem is stated a screwy way. It almost sounds as if it weighed 15.78 AFTER evaporation. I think the problem is two run on sentences.
15.78 = mass NaCl + H2O
3.26 = mass NaCl
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12.52 = mass H2O
% m/m = (mass NaCl/total mass)*100 =
You could do molality = mols/kg solvent.
%m/v = (mass NaCl/volume)*100 =
v = 15.0 mL
M = mols/L soln. mol = gNaCl/molar mass
kg solvent = 0.01252
To calculate the different concentrations, we need to first find the mass of the solute and the volume of the solution.
1. Calculate the mass of NaCl:
Mass of NaCl = Mass of the dry salt residue - Mass of the empty container
= 3.26 g - 0 g (assuming the container had negligible mass)
= 3.26 g
2. Calculate the volume of the solution:
Volume of the solution = Initial volume of the NaCl solution - Volume of water evaporated
= 15.0 mL - 0 mL (assuming no water evaporated)
= 15.0 mL
Now, we can calculate the different concentrations:
3. % (m/m) mass/mass percent:
% (m/m) = (mass of solute / mass of solution) x 100
= (3.26 g / 15.78 g) x 100
= 20.68%
4. % (m/v) mass/volume percent:
% (m/v) = (mass of solute / volume of solution) x 100
= (3.26 g / 15.0 mL) x 100
= 21.73%
5. Molarity (M):
Molarity = (moles of solute / volume of solution in liters)
To find the moles of solute, we need to convert the mass of NaCl (in grams) to moles using the molar mass of NaCl. The molar mass of NaCl is 58.44 g/mol.
Moles of NaCl = Mass of NaCl / Molar mass of NaCl
= 3.26 g / 58.44 g/mol
= 0.0558 mol
Now, we can calculate the molarity:
Molarity = (0.0558 mol / 0.015 L)
= 3.72 M
So, the concentrations are as follows:
% (m/m): 20.68%
% (m/v): 21.73%
Molarity: 3.72 M
To calculate the various concentrations, we need to first understand the definitions of %(m/m), %(m/v), and molarity (M).
1. %(m/m) or percent by mass: It is the mass of solute divided by the total mass of the solution, multiplied by 100. This concentration is usually expressed as a percentage.
2. %(m/v) or percent by volume: It is the volume of solute divided by the total volume of the solution, multiplied by 100. This concentration is also expressed as a percentage.
3. Molarity (M): It is the number of moles of solute (NaCl) divided by the volume of the solution in liters (L). Molarity is commonly used to express the concentration of a solution.
Now, let's calculate the given concentrations step by step:
1. Calculate %(m/m):
Step 1: Determine the mass of solute (NaCl):
Mass of NaCl = mass of solution - mass of empty container
Mass of NaCl = 15.78g - 3.26g
Mass of NaCl = 12.52g
Step 2: Calculate %(m/m):
%(m/m) = (mass of NaCl / mass of solution) * 100
%(m/m) = (12.52g / 15.78g) * 100
%(m/m) = 79.26%
Therefore, the %(m/m) concentration of the NaCl solution is 79.26%.
2. Calculate %(m/v):
Step 1: Determine the volume of solute (NaCl):
Volume of NaCl = volume of solution
Volume of NaCl = 15.0ml
Step 2: Calculate %(m/v):
%(m/v) = (volume of NaCl / volume of solution) * 100
%(m/v) = (15.0ml / 15.0ml) * 100
%(m/v) = 100%
Therefore, the %(m/v) concentration of the NaCl solution is 100%.
3. Calculate molarity (M):
Step 1: Determine the number of moles of solute (NaCl):
Moles of NaCl = mass of NaCl / molar mass of NaCl
The molar mass of NaCl is 58.44 g/mol.
Moles of NaCl = 12.52g / 58.44 g/mol
Moles of NaCl = 0.2140 mol
Step 2: Calculate molarity:
Molarity (M) = moles of NaCl / volume of solution in liters
Volume of solution = 15.0ml = 15.0 / 1000 L (since 1 L = 1000 ml)
Molarity (M) = 0.2140 mol / (15.0 / 1000 L)
Molarity (M) = 14.27 M
Therefore, the molarity (M) concentration of the NaCl solution is 14.27 M.