II III I II. Solution Concentration (p. 480 – 486) Ch. 16 – Solutions.
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Transcript of II III I II. Solution Concentration (p. 480 – 486) Ch. 16 – Solutions.
II
III
I II. Solution Concentration
(p. 480 – 486)
Ch. 16 – SolutionsCh. 16 – Solutions
A. ConcentrationA. Concentration
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
B. Percent SolutionsB. Percent Solutions
Percent By Volume (%(v/v))
• Concentration of a solution when both solute and
solvent are liquids often expressed as percent by
volume
100solution ofvolume
solute ofvolume (%(v/v))Volume by Percent
total combined volume
substance being dissolved
B. Percent SolutionsB. Percent Solutions
Find the percent by volume of ethanol (C2H6O) in a 250 mL solution containing 85 mL ethanol.
85 mL ethanol
250 mL solution = 34%
ethanol (v/v)
Solute = 85 mL ethanolSolution = 250 mL
% (v/v) = x 100
B. Percent SolutionsB. Percent Solutions
Percent By Mass (%(m/m))
• Concentration of a solution when solute is solid
sometimes expressed as percent by mass
100solution of mass
solute of mass(%(m/m)) Massby Percent
total combined volume
substance being dissolved
B. Percent SolutionsB. Percent Solutions
How much glucose should you use to make 2000. g of a 2.8% (m/m) solution in water?
unknown g glucose
2000. g solution= 56.00 g
glucose
Percent (m/m) = 2.8%Solution = 2000. g
2.8 = x 100
C. MolarityC. Molarity
Concentration of a solution most often
used by chemists
solution of liters
solute of moles(M)Molarity
total combined volume
substance being dissolved
C. MolarityC. Molarity
2M HCl
L
molM
nsol' L 1
HCl mol 2HCl 2M
What does this mean?
Molar Mass(g/mol)
6.02 1023
particles/mol
MASSIN
GRAMSMOLES
NUMBEROF
PARTICLES
Molar Volume (22.4 L/mol)
LITERSOF GASAT STP
LITERSOF
SOLUTION
Molarity(mol/L)
D. Molarity CalculationsD. Molarity Calculations
D. Molarity CalculationsD. Molarity Calculations
How many moles of NaCl are required to make 0.500L of 0.25M NaCl?
0.500 L sol’n 0.25 mol NaCl
1 L sol’n
= 0.013 mol NaClL 1
mol0.25 0.25M
D. Molarity CalculationsD. Molarity Calculations
How many grams of NaCl are required to make 0.500L of 0.25M NaCl?
0.500 L sol’n 0.25 mol NaCl
1 L sol’n
= 7.3 g NaCl
58.44 g NaCl
1 mol NaCl
L 1
mol0.25 0.25M
D. Molarity CalculationsD. Molarity Calculations
Find the molarity of a 250 mL solution containing 10.0 g of NaF.
10.0 g NaF 1 mol NaF
41.99 g NaF= 0.95 M
NaF
L
molM
.25 L sol’n
2211 VMVM
E. DilutionE. Dilution
Preparation of a desired solution by adding water to a concentrate
Moles of solute remain the same
E. DilutionE. 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
WORK:
M1 V1 = M2 V2
(15.8M) V1 = (6.0M)(250mL)
V1 = 95 mL of 15.8M HNO3
F. MolalityF. Molality
solvent ofkg
solute of moles(m)molality
mass of solvent only
1 kg water = 1 L water
kg 1
mol0.25 0.25m
G. Molality CalculationsG. Molality Calculations
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
G. Molality CalculationsG. Molality Calculations
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
mol1.54 1.54m
H. Preparing SolutionsH. Preparing Solutions
500 mL of 1.54M NaCl
500 mLwater
45.0 gNaCl
• mass 45.0 g of NaCl• add water until total
volume is 500 mL• mass 45.0 g of NaCl• add 0.500 kg of water
500 mLmark
500 mLvolumetric
flask
1.54m NaCl in 0.500 kg of water
H. Preparing SolutionsH. Preparing Solutions
250 mL of 6.0M HNO3 by dilution
• measure 95 mL of 15.8M HNO3
95 mL of15.8M HNO3
water for
safety
250 mL mark
• combine with water until total volume is 250 mL
• Safety: “Do as you oughtta, add the acid to the watta!” or AA – add acid!
Solution Preparation Mini-LabSolution Preparation Mini-Lab
Turn in one paper per team. Complete the following steps:
A) Show the necessary calculations.
B) Write out directions for preparing the solution.
C) Prepare the solution. For each of the following solutions:
1) 100.0 mL of 0.50M NaCl
2) 0.25m NaCl in 100.0 mL of water
3) 100.0 mL of 3.0M HCl from 12.0M concentrate. (don’t actually prepare this one!)