concentration
DESCRIPTION
Solutions. Concentration. Concentration Units. The amount of solute in a solution. Describing Concentration % by mass - medicated creams % by volume - rubbing alcohol ppm, ppb - water contaminants molarity - used by chemists molality - used by chemists. moles solute. =. Molarity. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/1.jpg)
II
III
I Concentration
Solutions
![Page 2: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/2.jpg)
Concentration Units
The amount of solute in a solution.
Describing Concentration
• % by mass - medicated creams
• % by volume - rubbing alcohol
• ppm, ppb - water contaminants
• molarity - used by chemists
• molality - used by chemists
![Page 3: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/3.jpg)
MolarityMolarityMolarityMolarity
Molarity (M) = moles soluteliters of solution
L
molM
L 1
mol0.25 0.25M
![Page 4: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/4.jpg)
PROBLEM: Dissolve 5.00 g of NiCl2•6 H2O (237.7 g/mol) in enough water to make 250 mL of solution. Calculate the Molarity.
PROBLEM: Dissolve 5.00 g of NiCl2•6 H2O (237.7 g/mol) in enough water to make 250 mL of solution. Calculate the Molarity.
Step 1Step 1: : Calculate moles of NiCl2•6H2O
5.00 g • 1 mol
237.7 g = 0.0210 mol
0.0210 mol0.250 L
= 0.0841 M
Step 2: Step 2: Calculate Molarity
[NiClNiCl22•6 H•6 H22O O = 0.0841 M
![Page 5: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/5.jpg)
Step 1: Change mL to L:250 mL * 1L/1000mL = 0.250 L
Step 2: Calculate Moles
= (0.0500 mol/L) (0.250 L) = 0.0125 moles
Step 3: Convert moles to grams.
(0.0125 mol)(90.00 g/mol) = 1.13 g
What mass of oxalic acid, H2C2O4, is required to make 250. mL of a 0.0500M solution?
What mass of oxalic acid, H2C2O4, is required to make 250. mL of a 0.0500M solution?
![Page 6: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/6.jpg)
Learning CheckLearning Check
How many grams of NaOH are required to prepare 400. mL of 3.0 M NaOH solution?
1) 12 g
2) 48 g
3) 300 g
![Page 7: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/7.jpg)
Two Other Concentration Two Other Concentration UnitsUnits
grams solutegrams solution
MOLALITY, m
% by mass =
% by mass
m of solution = mol solute
kilograms solvent
![Page 8: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/8.jpg)
Percent Composition
This is the mass of the solute divided by the mass of the solution (mass of solute plus mass of solvent), multiplied by 100.
Example: Determine the percent composition by mass of a 100 g salt solution which contains 20 g salt.
(20 g NaCl / 100 g solution) x 100 = 20% NaCl solution
![Page 9: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/9.jpg)
Molality
solvent ofkg
solute of moles(m)molality
mass of solvent only
1 kg water = 1 L waterkg 1
mol0.25 0.25m
![Page 10: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/10.jpg)
Calculating ConcentrationsCalculating Concentrations
Calculate molalityCalculate molality
Calculate molalityCalculate molality
Dissolve 62.1 g (1.00 mol) of ethylene glycol in 250. g of H2O.
Calculate m & % of ethylene glycol (by mass).
Dissolve 62.1 g (1.00 mol) of ethylene glycol in 250. g of H2O.
Calculate m & % of ethylene glycol (by mass).
conc (molality) = 1.00 mol glycol0.250 kg H2O
4.00 molal
%glycol = 62.1 g
62.1 g + 250. g x 100% = 19.9%
Calculate weight %
![Page 11: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/11.jpg)
Molality
Find the molality of a solution containing 75 g of MgCl2 in 250 mL of water.
75 g MgCl2 1 mol MgCl2
95.21 g MgCl2
= 3.2m MgCl2
0.25 kg water
kg
molm
![Page 12: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/12.jpg)
Molality
How many grams of NaCl are req’d to make a 1.54m solution using 0.500 kg of water?
0.500 kg water 1.54 mol NaCl
1 kg water
= 45.0 g NaCl
58.44 g NaCl
1 mol NaCl
kg 1
mol1.5 1.5m
![Page 13: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/13.jpg)
2211 VM=VM
Dilutions
Preparation of a desired solution by adding water to a concentrate.
Moles of solute remain the same.
![Page 14: Concentration](https://reader034.vdocuments.site/reader034/viewer/2022051517/56814fe7550346895dbdb35f/html5/thumbnails/14.jpg)
Dilution
What volume of 15.8M HNO3 is required to make 250 mL of a 6.0M solution?
GIVEN:
M1 = 15.8M
V1 = ?
M2 = 6.0M
V2 = 250 mL
= 0.250 L
WORK:
M1 V1 = M2 V2
(15.8M) V1 = (6.0M)(0.250 L)
V1 = 0.095 L of 15.8M HNO3