chapter 6: sports drink. sports drinks this chapter will introduce the chemistry needed to...
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Sports Drinks
This chapter will introduce the chemistry needed to understand how Sports Drinks workSection 6.1: Solutions & electrolytesSection 6.2: Concentrations of solutionsSection 6.3: Acidity & pHSection 6.4: Solubility & precipitatesSection 6.5: StoichiometrySection 6.7: Limiting ReactantsSection 6.6: Properties of solutions
Section 6.1—Solutions & Electrolytes
What are those “electrolytes” they say you’re replacing by drinking sports drinks?
Dissolving substances
Substances are dissolved by a process called hydration when the solvent is waterThe solvent and solute need to break
intermolecular forces within themselves- This requires ENERGY (ENDOTHERMIC)
New intermolecular forces are formed between the solvent and solute.- This releases ENERGY(EXOTHERMIC)
The solvent “carries off” the solute particles
Dissolving Ionic Compounds
- +
+
+
+
-
--
-
+
-
OH H - +Solvent,water
Solute,Ionic compound
Water molecules are polar and they are attracted to the charges of the ions in an ionic compound.
When the intermolecular forces are stronger between the water and the ion than the intramolecular forces between the ions, the water carries away the ion.
- +
+
-
--
-
+
+
Dissolving Ionic Compounds
+
-
OH H - +water
Ionic compound
As more ions are “exposed” to the water after the outer ions were “carried off”, more ions can be “carried off” as well.
Dissolving Ionic Compounds
+
-
OH H - +water
Ionic compound
- +
+
+
+
-
--
-
These free-floating ions in the solution allow electricity to be conducted
Electrolytes
When there are free-floating charges in a solution then it can conduct electricity.
Things that produce free-floating charges when dissolved in water are called electrolytes.
Dissolving Covalent Compounds
- +
- +
- + - +- +
Solvent, water (polar)
+
-
- + Solute, sugar (polar)
Polar covalent molecules are formed in the same way—water forms intermolecular forces with the solute and “carries” the solute particles away.
Dissolving Covalent Compounds
Solvent, water (polar)
+
-
- + Solute, sugar (polar)
- +
- +
- +- + - +
However, the polar covalent molecules stay together and just separates from other solute molecules. NO charged ions form.
Non-electrolytes
When molecules separate from other molecules, but free-floating charges are not produced, the solution cannot conduct electricity.
These are called
non-electrolytes
Types of Electrolytes
Strong Electrolytes
SolubleIonic compounds
Strong Acids & Bases
Weak Electrolytes
InsolubleIonic Compounds
Weak Acids & Bases
Non-Electrolytes
Covalent Compounds except for ACIDS & BASES
Almost all ions are separated when
dissolved in water.
Only a few ions are separated when
dissolved in water
No molecules separate—ions are
not formed
Easily conducts electricity when
dissolved in water
Conducts electricity slightly when
dissolved in water
Does not conduct electricity at all when
dissolved in water
Breaking up Electrolytes
Leave polyatomic ions in-tact (including the subscript within the polyatomic ion)
All subscripts not within a polyatomic ion become coefficients
Be sure to include charges on the dissociated ions!
Example:Break up the following ionic
compounds into their ions
KNO3
Ca(NO3)2
Na2CO3
Breaking up Electrolytes
Leave polyatomic ions in-tact (including the subscript within the polyatomic ion)
All subscripts not within a polyatomic ion become coefficients
Be sure to include charges on the dissociated ions!
Example:Break up the following ionic
compounds into their ions
KNO3
Ca(NO3)2
Na2CO3
K+1 + NO3-1
Ca+2 + 2 NO3-1
2 Na+1 + CO3-2
Misconceptions about dissolving
People often describe something that dissolves as having “disappeared”
Before the solute dissolves, it’s in such a large group of particles that we can see it.
After dissolving, the solute particles are still there—they’re just spread out throughout the solution and are in groupings so small that our eyes can’t see them
Types of Solutions
SOLID-LIQUID
Salt Water
LIQUID-SOLID
Dental Filling (Mercury in Silver)
GAS-LIQUID
SODA(Carbon dioxide gas
in water)
When 2 substances dissolve in one another, they are considered SOLUBLEIf they cannot dissolve in one another, they are INSOLUBLE
A solution is made of two parts:SOLUTE: the substance that is dissolved; usually in minoritySOLVENT: The substance that does the dissolving, usually in majority
Types of Solutions
SOLID-SOLID
ALLOYS(brass, bronze,
sterling silver, steel)
LIQUID-LIQUID
Alcohol & waterAcetic acid in water(vinegar)
GAS-GAS
AIR(Oxygen in Nitrogen
gas)
When 2 liquids dissolve in one another, they are considered MISCIBLEIf they cannot dissolve in one another, they are IMMISCIBLE.
Types of Solutions
Unsaturated
Not full- we can add solute to the solvent
& it will dissolveVisual-no solid on
bottom
Saturated
It’s “Full”- no more solute can be
dissolvedVisual- solid can be seen at the bottom
Super-Saturated
Has more solute dissolved than a
saturated solution has at room temperature
No visual- need some background
information
A SUPERSATURATED SOLUTION
A supersaturated solution can be seeded. This is a solution at room temperature that has beyond the maximum amount of solid it can dissolve.
Solubility of a Gas vs LiquidIn general,
• the higher the temperature of a solution, more solid can be dissolved.
• the higher the temperature of a solution, less gas can dissolve. Thermal Pollution!
Henry’s Law
As the pressure above a liquid increases, the solubility of a gas within a liquid will increase
Reading a Solubility CurveFind the data point on the graph of the temperature and solubility of solute in solvent.•If it is below the line, it is UNSATURATED•IF it is on the line, it is SATURATED•If it is above the line, the difference between the point and the line is the extra amount that is sitting at the bottom.
Reading a Solubility CurveExamples1.What kind of solution occurs when 40g of KCl is dissolved in 100 g H2O at 60ºC?
2.What kind of solution occurs when 40g of KCl is dissolved in 100 g H2O at 40ºC? 3.What is the maximum amount of NaBr that can be dissolved in 100 g H2O at 60ºC?
unsaturated
saturated
120 g
Reading a Solubility CurveExamples4. What is the maximum amount of KNO3 that can be dissolved at 70ºC? 5. According to the diamond mark, How much of the KNO3 has been added to the water at 70ºC?
6. How much extra KNO3 is sitting at the bottom of the container at this temperature of 70ºC?
140g
160g
20g
ConcentrationA measure of the amount of solute in a given
amount of solutionQualitative Description:
Dilute: small amount of solute compared to solvent
Concentrated: large amount of solute compared to solvent
Concentrated Dilute
Concentrated versus Dilute
solute solvent
Lower concentration
Not as many solute (what’s being dissolved) particles
Higher concentration
More solute (what’s being dissolved) particles
Molarity: a quantitiative description of concentrationMolarity (M) is a concentration unit that uses moles
of the solute instead of the mass of the solute
2M solution is 2 moles of solute dissolved in 1.0 L of solution
solutionL
solutemolesM
moles
Molarity Liters X
Molarity ExampleExample:
If you dissolve 5.0 moles of NaCl in
300.0 mL of water, what is the molarity?
Molarity Example
L
molesM
300.0
0.5
Example:If you dissolve 5.0 moles of NaCl in
300.0 mL of water, what is the molarity?
solventL
solutemolesM 17 M NaCl
Remember to change mL to L! 300. mL of water = 0.300 L
Molarity Example
L
molesM
150.0
21.0
Example:If you dissolve 12 g of NaCl in 150 mL of water, what is
the molarity?
solventL
solutemolesM 1.4 M NaCl
12 g NaCl = _______ mole NaClg NaCl
mole NaCl1
58.44
0.21
1 mole NaCl molecules = 58.44 g
NaCl
11
22.99 g/mole35.45 g/mole
= 22.99 g/mole= 35.45 g/mole+
58.44 g/mole
Remember to change mL to L! 150 mL of water = 0.150 L
Molarity ExampleExample:
How many grams of CaCl2 would be needed to make
25.0 ml of a 2.5M solution?
Molarity Example
L
XmolesM
0250.5.2
Example:How many grams of CaCl2 would be needed to make
25.0 ml of a 2.5M solution?
solventL
solutemolesM .0625 moles NaCl
.063 mol CaCl2 = 6.9 grams CaCl2
CaCl2
g CaCl2 110.98
1 mol
1 mole CaCl2 = 110.98 g
CaCl
12
40.01 g/mole35.45 g/mole
= 40.08 g/mole= 70.90 g/mole+
110.98 g/mole
Remember to change mL to L! 25 mL of water = 0.025 L
How to Make a Solution Make 500.0 ml of a .12 M solution of CoCl22H2O
1st: Convert your moles of solute to grams.
.12 M x .500L = .060 moles solute
.060 moles x 165.87 g/1mol = 9.948 g
(10. g) 2nd : Add solute amount to a
volumetric flask.
Add 10.0 g cobalt chloride to flask
3rd : Add enough solvent to make the required amount of solution and stir.
In this case, the solvent is ethanol. Add slowly until 500 ml of solution is reached.
Dilution: A technique used to make a dilute solution from a Concentrated Solution
= .0050 mol .10 L
= .050 M I2
= .0050 mol .50 L
= .010 M I2
How to Calculate a Dilution
M1V1= M2V2
moles1 = moles2
M1V1 = original (stock) concentration &
volumeM2V2 = new concentration & volume
You do not have to change your volume to liters!
Example:
What is the molarity of a new solution if you diluted 100.0 ml of 3.0M HCl to 250.0 ml?
Example:What is the molarity of a new solution if you
diluted 100.0 ml of 3.0 M HCl to 250.0 ml?
M1V1= M2V2
(3.0M)(100.0ml) = (X)(250.0 ml)
300.0 Mml= 250.0ml x
250.0 ml 250.0ml
X= 1.2 M
Review of Acids – Arrhenius Definition
Acids produce Hydronium ion (H3O+1) in water
Hydronium ion is water + a hydrogen cation
H
OH
water
H+1
H
OH
H +1
A new of definition of an ACID: According to Bronsted-Lowry
An acid is a hydrogen (proton) donor
The substance that remains after the hydrogen has been donated is called the conjugate base
Example: NH3 + H2O OH- + NH4+
acid conjugate base
A new of definition of a BASE: According to Bronsted-Lowry
A base is a hydrogen (proton) acceptor
The substance that forms after the hydrogen has been accepted is called the conjugate acid
Example: NH3 + H2O OH- + NH4+
base conjugate acid
Conjugate Acid-Base Pairs
ACIDS & BASES WILL ALWAYS BE ON THE REACTANT SIDE
CONJUGATE ACIDS & BASES WILL ALWAYS BE ON THE PRODUCT SIDE
Practice Problems: Label the acid & base on the left side of the reaction and the conjugate acid & conjugate base on the right side.
a) HCl + H2O H3O+ + Cl−
______ ______ ______ ______
b) HCO3-1 + H2O H2CO3 + OH−
_____ ______ ______ ______
acid base C.A. C.B.
base acid C.A. C.B.
Characteristics of Acids & BasesBasesAcids
Produce H3O+1 (hydronium ion) in water
Produce OH-1 (hydroxide ion) in water
Tastes sour Tastes Bitter
React with active metals to form hydrogen gas
Feels slippery
Turns red litmus blueTurns pink in phenlphthalien
Turns blue litmus redTurns clear in phenolphthalien
React with bases to form salt and water (neutralization
reaction)
React with acids to form salt and water (neutralization
reaction)
Both are considered electrolytes
Strong versus Weak Acids
+
++
-
-
-
In a Strong acidMost of the acid molecules
have donated the H+1 to water
How many hydronium ion – anion pairs can you find?
How many intact acid molecules can you find?
3
1
Strong versus Weak Acids
+
-
In a Weak acidOnly a few of the acid
molecules have donated the H+1 to water
How many hydronium ion – anion pairs can you find?
How many intact acid molecules can you find?
1
3
Acids and Bases as Electrolytes
Acids and bases dissociate into ions in water
Free-floating ions in water conduct electricity
Acids & Bases are electrolytes
Strong acids and bases are strong electrolytesWeak acids and bases are weak electrolytes
Is a measure the acidity of a sample
pH Scale
0 14
Highly acidic Very basic (not acidic)
neutral
7
Acids have a pH that are less than 7.0Bases have pH values that are more than 7.0Neutral is considered a pH of 7.0
less acidic, more basic
more acidic, less basic
Calculating pH
pH scale – Logarithmic scale of the acidity of a solution
The pH scale uses base “10”
]log[ 13
OHpH
pHOH 10][ 13
pH has no units
[ ] = concentration in Molarity
The formula for calculating pH
The formula for calculating hydronium ion concentration
The “-” in the pH equation
Concentration of Hydronium ion versus pH
0
0.5
1
0 0.5 1 1.5 2
pH
[H3
O+
]
Because pH is the negative log of concentration of hydronium, as concentration increases, the pH goes down.
The lowest pH is the highest concentration of hydronium ion
What does a “log” scale really mean?
pH
4
3
2
1
10x more acidic
100x more acidic
1000x more acidic
Leve
l of
acid
ity in
crea
ses
Every change of 1 in pH shows a change of 10x in concentration of hydronium
Example
The pH of a solution changes from a pH of 5 to a pH of 3.
a.Did it increase or decrease in hydrogen ion concentration?
b.By what factor did it change?
An example of calculating pH
pH = 8.00
]log[ 13
OHpH
)80.1log( epH
Example:Find the pH if the concentration of
[H3O+1] is 1.0 x 10-8 M
An example of calculating hydronium
H3O+1 = 1 x 10-5 M
pHOH 10][ 13
513 10][ OH
Example:Find the [H3O+1] if
the pH is 5.0
Auto-ionization of Water
Water molecules collide spontaneously and will split into ions. This is called auto-ionization
H2O + H2O H3O+1 + OH-1
At 25°C the following is true:
[H3O+1] × [OH-1] = 1.0 × 10-14 M2
Hydrogen Ion Concentration ValuesIf the hydrogen ion concentration is greater than
hydroxide ion, the solution is ACIDIC with a pH < 7[H+] > [OH-] or[H+] > 1.0 x 10-7 M
If the hydrogen ion concentration is less than hydroxide ion, the solution is BASIC with a pH > 7[H+] < [OH-] or[H+] < 1.0 x 10-7 M
If the hydrogen ion concentration is equal to hydroxide ion, the solution is NEUTRAL with a pH = 7[H+] = [OH-] = 1.0 x 10-7 M
Calculating pOH
]log[ 1 OHpOH
pOHOH 10][ 1
[ ] = concentration in Molarity
The formula for calculating pOH
The formula for calculating hydroxide ion concentration
To relate pH and pOH 14 pHpOH
Let’s Practice #3: 2 ways to do this…1st way
14113 101][][ OHOH
1419 101][]100.1[ OH
Example:Find the [OH-1] if
the [H+] is 1.0 x10-9
]100.1[
101][
9
141
OH
[OH-] = 1.0 x10-5 M
Let’s Practice #3: 2 ways to do this…2nd way
Example:Find the [OH-1] if
the [H+] is 1.0 x10-9
[OH-] = 1.0 x10-5 M
]log[ 13
OHpH
14 pHpOHpH = 9.00
pOH + 9.00 = 14
pOH = 5.00
pOHOH 10][ 1
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