SOLUTIONS A solution is a homogeneous mixture of a solute dissolved in a solvent. The solvent is...
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Transcript of SOLUTIONS A solution is a homogeneous mixture of a solute dissolved in a solvent. The solvent is...
SOLUTIONS
A solution is a homogeneous mixture of a solute dissolved in a solvent.
The solvent is generally in excess.
ExampleThe solution NaCl(aq) is sodium chloride NaCl(s) dissolved in water H2O(l)
The solute is NaCl(s) and the solvent is H2O(l)
Solute + solvent
Solutions: homogeneous mixtures
• Two components (at the least)-– Solute – the substance being dissolved– Solvent – the dissolving medium
• usually water – aqueous solution
can have multi-solute solutions - seawater
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Solubility experiment
Different solutions
• It’s possible to prepare solutions in all phases of matter.
Different solutions
However,
• The solutions in which the solvent is water are called “AQUEOUS SOLUTIONS.”
• Aqueous solutions are indicated as (aq) in reaction equations.
Ni(s) + HCl(aq) NiCl2(aq) + H2(g) NiCl2(s)dry
Aqueous solutions
Types of Solutions
• Are solutions made from only one solvent and one solute?
– By definition, there can only be one solvent– However, many solutes can be dissolved in a
solvent to create a solution• Air is an example of a solution with one “solvent” (nitrogen) and many “solutes” (oxygen, helium, argon, carbon dioxide, etc.)
Unsaturated solution- a solution that is able to dissolve more solute.
Saturated solution- a solution that cannot dissolve any more solute at the given conditions.
Supersaturated solution- a solution holding more dissolved solute than is specified by its solubility at a given temperature
Electrolyte and Non-electrolyte
• Electrolyte: a substance that conducts electricity when dissolved in water. – Acids, bases and soluble ionic
solutions are electrolytes.
• Non-electrolyte: a substance that does not conduct electricity when dissolved in water. – Molecular compounds and insoluble
ionic compounds are non-electrolytes.
Electrolytes
• Some solutes can dissociate into ions.
• Electric charge can be carried.
Types of solutes
Na+Cl-
Strong Electrolyte -100% dissociation,all ions in solution
high conductivity
Types of solutes
CH3COOH
CH3COO-H+
Weak Electrolyte -partial dissociation,molecules and ions in solution
slight conductivity
Types of solutes
sugar
Non-electrolyte -No dissociation,all molecules in solution
no conductivity
Strong ElectrolytesStrong acids: HNO3, H2SO4, HCl, HClO4
Strong bases: MOH (M = Na, K, Cs, Rb etc)
Salts: All salts dissolving in water are completely ionized.
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Concentration • the amount of solute dissolved in a
solvent at a given temperature
described as dilute if it has a low concentration of solute
described as concentrated if it has a high concentration of solute
described as supersaturated if contains more dissolved solute than normally possible
Units of Concentrations
amount of solute per amount of solvent or solution
Molarity (M) =
moles of solute(n)
volume in liters of solution (V)
moles = M x V(L)
Examples:
Example 1: What is the concentration when 5.2 moles of hydrosulfuric acid are dissolved in 500 mL of water?
Step one: Convert volume to liters, mass to moles. 500 mL = 0.5 L
Step two: Calculate concentration. C = 5.2 mol/0.5 L = 10mol/L
• Example 2: What is the volume when 9.0 moles are present in
5.6 mol/L hydrochloric acid?
• Example 3: How many moles are present in 450 mL of 1.5
mol/L calcium hydroxide?
• Example 4: What is the concentration of 5.6 g of magnesium
hydroxide dissolved in 550 mL?
• Example 5: What is the volume of a 0.100 mol/L solution that
contains 5.0 g of sodium chloride?
Answers2) 9.0/5.6=1.6071428= 1.6 L
3) 1.5x0.45= 0.675=0.68 mol
4) Mg(OH)2= 58.316 g/mol
5.6/58.316=0.0960285342 mol
0.0960285342/0.55 = 0.1745973349 M
0.17 M
5) NaCl=58.5 g/mol
5.0/58.5= 0.0854700855 mol
0.0854700855 mol/0.100= 0.8547008547L
0.85 L
HOW MUCH SOLUTE IS NEEDED FOR A SOLUTION OF A PARTICULAR
MOLARITY AND VOLUME?
• EXAMPLE
How much solute is required to make 300 mL of 0.8 M CaCl2?
ANSWER
(111.0 g) (0.8 mole) (0.3 L) = 26.64 g
mole L
CaCl2
CaCl2
CaCl2 solution
CaCl2
EXAMPLE: Prepare 1 L, 1M Na2SO4 solution.
PREPARING DILUTE SOLUTIONS FROM CONCENTRATED ONES
• Concentrated solution = stock solution• Use this equation to decide how much
stock solution you will need: M1V1=M2V2
M1 = concentration of stock solution
M2 = concentration you want your dilute solution to be
V1 = how much stock solution you will need
V2 = how much of the dilute solution you want to make
EXAMPLE
• How would you prepare 1000 mL of a 1 M solution of KCl from a 3 M stock of the solution of KCl ?– The concentrated solution is 3 M, and is M1.
– The volume of stock needed is unknown, ?, and is V1.
– The final concentration required is
1 M, and is M2.
– The final volume required is 1000 mL and is V2.
SUBSTITUTING INTO THE EQUATION:
M1 .V1 = M2 .V2
3 M (?) 1 M (1000 mL)
? = 333.33 mL
So, take 333.33 mL of the concentrated stock solution and BTV (Bring to Volume)1 L.
EXAMPLE
• How would you prepare 500 mL of a 1.2 M solution of NaNO3 from a 2 M stock of the solution of NaNO3 ?– The concentrated solution is 2 M, and is M1.
– The volume of stock needed is unknown, ?, and is V1.
– The final concentration required is
1.2 M, and is M2.
– The final volume required is 500 mL and is V2.
SUBSTITUTING INTO THE EQUATION:
M1 .V1 = M2 .V2
2 M (?) = 1.2 M (500 mL)
? = 300 mL
So, take 300 mL of the concentrated stock solution and BTV (Bring to Volume)500 mL.