SOLUTIONS
Solution Formation Electrolytes Acids and Bases Strong and Weak Acids and Bases Concentration Percent Concentration Molarity Molar-Solutions-Solids
Solutions Solutes Solvents
Water
Most common solvent A polar molecule
OH a hydrogen bond
HH + HH +
Hydrogen Bonds Attract Polar Water Molecules
Solute and Solvent
Solutions are homogeneous mixtures of two or more substances
Solute
The substance in the lesser amount
Solvent The substance in the greater amount
Nature of Solutes in Solutions
Spread evenly throughout the solution Cannot be separated by filtration Can be separated by evaporation Not visible, solution appears transparent May give a color to the solution
Types of Solutions
air soda seawater brass O2 gas and N2 gas CO2 gas in water NaCl in water copper and zinc gas/gas gas/liquid solid/liquid solid/solid
Discussion
Give examples of some solutions and explain why they are solutions.
Learning Check SF1
(1) element A. water B. sugar C. salt water D. air E. tea (2) compound 1 1 1 1 1 2 2 2 2 2 (3) solution 3 3 3 3 3
LecturePLUS Timberlake
Solution SF1
(1) element A. water B. sugar C. salt water D. air E. tea (2) compound 2 2 3 3 3
LecturePLUS Timberlake 10
(3) solution
Learning Check SF2
Identify the solute and the solvent. A. brass: 20 g zinc + 50 g copper solute = 1) zinc 2) copper solvent = 1) zinc 2) copper
B. 100 g H2O + 5 g KCl solute solvent = = 1) KCl 1) KCl 2) H2O 2) H2O
Solution SF2
A. brass: 20 g zinc + 50 g copper solute solvent = = 1) zinc 2) copper
B. 100 g H2O + 5 g KCl solute solvent = = 1) KCl 2) H2O
Learning Check SF3
Identify the solute in each of the following solutions: A. 2 g sugar (1) + 100 mL water (2) B. 60.0 mL ethyl alcohol(1) and 30.0 mL of methyl alcohol (2) C. 55.0 mL water (1) and 1.50 g NaCl (2) D. Air: 200 mL O2 (1) + 800 mL N2 (2)
Solution SF3
Identify the solute in each of the following solutions: A. 2 g sugar (1) B. 30.0 mL of methyl alcohol (2) C. 50 g NaCl (2) D. 200 mL O2 (1)
Like dissolves like
A ____________ solvent such as water is needed to dissolve polar solutes such as sugar and ionic solutes such as NaCl. A ___________solvent such as hexane
(C6H14) is needed to dissolve nonpolar solutes such as oil or grease.
Learning Check SF4
Which of the following solutes will dissolve in water? Why? 1) Na2SO4 (ionic) 2) gasoline (nonpolar) 3) I2 (nonpolar) 4) HCl (polar)
Solution SF4
Which of the following solutes will dissolve in water? Why? 1) Na2SO4 2) gasoline 3) I2 4) HCl Yes, ionic No, nonnpolar No, nonpolar Yes, Polar
Formation of a Solution
H2 O
Na+
Hydration
Cl- Na+ H2O ClNa+ ClLecturePLUS Timberlake solute
Dissolved solute
Writing An Equation for a Solution
When NaCl(s) dissolves in water, the reaction can be written as H 2O NaCl(s)
solid
Na+ (aq) + Cl- (aq)
separation of ions in water
Practice Exercise #1
Solid LiCl is added to some water. It dissolves because A. The Li+ ions are attracted to the 1) oxygen atom(H-) of water 2) hydrogen atom(H+) of water B. The Cl- ions are attracted to the 1) oxygen atom(H-) of water 2) hydrogen atom(H+) of water
Solution PE#1
Solid LiCl is added to some water. It dissolves because A. The Li+ ions are attracted to the 1) oxygen atom(H-) of water B. The Cl- ions are attracted to the 2) hydrogen atom(H+) of water
Rate of Solution
You are making a chicken broth using a bouillon cube. What are some things you can do to make it dissolve faster?
Crush it Use hot water (increase temperature) Stir it
Practice Exercise #2
You need to dissolve some gelatin in water. Indicate the effect of each of the following on the rate at which the gelatin dissolves as (1) increase, (2) decrease, (3) no change A. ___Heating the water B. ___Using large pieces of gelatin C. ___Stirring the solution
Solution PE#2
You need to dissolve some gelatin in water. Indicate the effect of each of the following on the rate at which the gelatin dissolves as (1) increase, (2) decrease, (3) no change A. 1 Heating the water B. 2 Using large pieces of gelatin C. 2 Stirring the solution
Electrolytes
Are substances that form positive(+) and negative (-) ions in water
Conduct an electric current
Conductivity of Electrolytes
The conductivity of solutions can be tested by using an ohmmeter such as the one shown here. When there is little or no electrical conductivity between the probes the needle on the meter points to the left of the scale ("infinite" ohms).
When there is very good electrical conductivity between the probes (as when they are touching) the needle on the meter points to the right of the scale (0 ohms).
When the probes are placed in water, as shown here, you can see that the meter needle is still far to the left. Pure water does not conduct electricity very well.
When the probes are placed in a solution containing sodium chloride, the meter needle moves quite a ways to the right showing that the solution conducts electricity very well. Thus, sodium chloride is a strong electrolyte.
When the probes are placed in a solution containing sugar, the meter needle does not appear to move away from the left end of the scale showing that the solution does not conduct electricity any better than pure water. Thus, sugar is a nonelectrolyte.
When the probes are placed in a solution containing vinegar (acetic acid), the meter needle moves somewhat to the right showing that the solution conducts electricity somewhat. Thus, acetic acid is a weak electrolyte.
Strong Electrolytes are 100% ionized
salts NaCl(s) H 2O CaBr2(s) acids HCl(g) H 2O H3O+(aq) + Cl-(aq) Ca2+(aq) + 2Br- (aq) H 2O 100%ions Na+(aq) + Cl-(aq)
Weak electrolytes
Most of the solute exists as molecules in
solution Only a few solute particles produce ions HF + acid H 2O
p H3O+(aq) + F- (aq) p NH4+(aq) + OH- (aq)
NH3 + H2O base
Nonelectrolytes
Dissolve as molecules only No ions are produced in water Do not conduct an electric current H 2O C6H12O6 (s) p C6H12O6 (aq) glucose
Practice Exercise #3
Select the products for each of the following in water: H 2O A. CaCl2 (s) H 2O B. K3PO4 (s) 1) 3K+ , PO432) K3PO4 3) K3+ , P3-, O41) CaCl2 3) Ca2+ + 2Cl2) Ca2+, Cl2-
Solution PE#3
Select the products for each of the following in water:
H2 O A. CaCl2 (s) H2 O B. K3PO4 (s) 1) 3K+ + PO433) Ca2+ + 2Cl-
Acids and Base Reactions
According to the Brønsted definitions, some substances have properties associated with both acids and bases. Such substances are called amphoteric. In this case, the Hydrogen carbonate can either lose a proton to act like an acid or gain a proton to act like a base.
Arrhenius Acids and Bases
Acids produce H+ in aqueous solutions
water
HCl
H+(aq) + Cl- (aq)
Bases produce OH- in aqueous solutions
water
NaOH
Na+(aq) + OH- (aq)
Acids
Produce H+ (as H3O+) ions in water Produce a negative ion (-) too Taste sour Corrode metals React with bases to form salts and water
Bases
Produce OH- ions in water
Taste bitter, chalky Are electrolytes Feel soapy, slippery React with acids to form salts and water
Practice Exercise #4
Identify each as characteristic of an A) acid or B) base ____ 1. Sour taste ____ 2. Produces OH- in aqueous solutions ____ 3. Chalky taste ____ 4. Is an electrolyte ____ 5. Produces H+ in aqueous solutions
Solution PE#4
Identify each as a characteristic of an A) acid or B) base _A_ 1. Sour taste _B_ 2. Produces OH- in aqueous solutions _B_ 3. Chalky taste A, B 4. Is an electrolyte _A_ 5. Produces H+ in aqueous solutions
Some Common Acids
HCl HNO3 hydrochloric acid nitric acid
H3PO4
phosphoric acid sulfuric acid acetic acid
H2SO4 CH3COOH
Practice Exercise #5
Give the names of the following 1. bromic acid A. HBr (aq) 2. bromous acid 3. hydrobromic acid B. H2CO3 1. carbonic acid 2. hydrocarbonic acid 3. carbonous acid
Solution PE#5
A. HBr 3. hydrobromic acid The name of a nonoxy acid begins with the prefix hydro- and ends with -ic acid. In a nonoxy acid, the negative anion end in -ide. B. H2CO3 1. carbonic acid The name of an oxyacid is named with the stem of the anion (carbonate) changed to -ic acid
Practice Exercise #6
Acid, Base or Salt CaCl2 KOH ______ ______ Name _________________ _________________ _________________ _________________ _________________
Ba(OH)2 ______ HBr H2SO4 ______ ______
Solution PE#5
Acid, Base or Salt CaCl2 KOH salt base Name
Bronsted-Lowry Acids
Acids are hydrogen ion (H+) donors Bases are hydrogen ion (H+) acceptors HCl
donor
+ +
H 2O
acceptor
H 3O+
+
+ +
Cl-
Strengths of Acids and Bases
Strong acids completely ionize (100%) in aqueous solutions HCl + H2O H3O+ + Cl- (100 % ions)
Strong bases completely (100%) dissociate into ions in aqueous solutions. NaOH Na+ (aq) + OH-(aq) (100 % ions)
NH3, A Bronsted-Lowry Base
When NH3 reacts with water, most of the reactants remain dissolved as molecules, but a few NH3 reacts with water to form NH4+ and hydroxide ion. NH3 acceptor + H2 O donor NH4+(aq) + OH- (aq)
+
+
Strong and Weak Acids and Bases
Strong acids HCl, HNO3 , H2SO4 Most other acids are weak. Strong bases NaOH, KOH, and Ca(OH)2 Most other bases are weak.
Practice Exercise #6
Identify each of the following as a 1) strong acid or base 2) weak acid 3) weak base A. ___ HCl (aq) B. ___ NH3(aq) C. ___ NaOH (aq) D. ___ H2CO3 (aq)
Solution PE#6
Identify each of the following as a 1) strong acid or base 2) weak acid 3) weak base A. _1__ HCl (aq) B. _3__ NH3(aq) C. _1__ NaOH (aq) D. _2__ H2CO3 (aq)
More Antacids
Milk of Magnesia: Mg(OH)2
Rolaids:
AlNa(OH)2CO3 aluminum sodium dihydroxy carbonate
Tums: Tempo:
CaCO3 CaCO3, Al(OH)3, Mg(OH)2
Dilutions
Add water Volume increases. New concentration is less than initial
Concentration of A Diluted Solution
A 25 mL sample of a 6.0 M KOH is diluted by adding 75 mL of water. Calculate the new concentration of the KOH solution. Moles KOH = 0.025 L x 6.0 moles = 0.15 moles 1L New volume = 25 mL + 75 mL = 100. mL = 0.100 L New molarity = 0.15 moles = 1.5 M 0.100 L
Practice Exercise #7
A 125 mL sample of a 3.0 M HCl is diluted by adding 250 mL of water. The new concentration of the HCl solution is 1) 8.0 M 2) 1.5 M 3) 1.0 M
Solution PE#7
3) 1.0 M moles HCl = 0.250 L x 3.0 moles = 0.75 mole 1L new M = 0.75 mole 0.750 L 1.0 M HCl
Practice Exercise #8
A 50.0 mL sample of 15% sucrose solution is diluted by adding 200. mL of water. The new concentration of the sucrose solution is 1) 3.0 % 2) 7.5 % 3) 10. %
Practice Exercise #8
A 50.0 mL sample of 15% sucrose solution is diluted by adding 200. mL of water. The new concentration of the sucrose solution is 1) 3.0 % g sucrose = 50.0 mL x 15 g sucrose = 7.5 g 100 mL new % = 7.5 g sucrose = 3.0 % sucrose 250 mL
Making Molar Solutions
From Solids
What are molar solutions?
A molar solution is one that expresses ³concentration´ in moles per volume
Usually the units are in mol/L mol/L can be abbreviated as M or [ ]
Molar solutions are prepared using: a balance to weigh moles (as grams) a volumetric flask to measure litres L refers to entire volume, not water! Because the units are we can use the equation M = n/L mol/L,
Alternatively, we can use the factor label method
Calculations with molar solutions
Q: How many moles of NaCl are required to make 7.5 L of a 0.10 M solution? M=n/L, n = 0.10 M x 7.5 L = 0.75 mol
# mol NaCl = 7.5 L x 0.10 mol NaCl 1L = 0.75 mol
But in the lab we weigh grams not moles, so« Q: How many grams of NaCl are required to make 7.5 L of a 0.10 M solution?
# g NaCl = 7.5 L x 0.10 mol NaCl 1L x 58.44 g NaCl 1 mol NaCl =43.83 g
19.
# g NaOH = x 0.125 mol NaOH 1L x 40.00 g NaOH 1 mol NaOH x 58.44 g NaCl 1 mol NaCl = 164 g =15.0 g
3.00 L
20. # g NaCl =
5.0 L
x 0.56 mol NaCl 1L
21. 355 ppm = 355 mg/L or 0.355 g/L
# g CO2 = 0.355 g CO2 1.00 L x 0.355 g CO2 1L x 1 mol CO2 44.0 g CO2 =.355 g
= 8.07 x 10±3 mol z 1L = 8.07 x 10±3 mol/L
22. a) 235 g z 3000 mL x 100% =7.83 % W/V
b) mol/L = 4.02 mol / 3.00 L = 1.34 mol/L
More Practice Questions
1. How many grams of nitric acid are present in 1.0 L of a 1.0 M HNO3 solution? 63 g 2. Calculate the number of grams needed to produce 1.00 L of these solutions: a) 1.00 M KNO3 b) 1.85 M H2SO4 c) 0.67 M KClO3 101 g 181 g 82 g
3.Calculate the # of grams needed to produce each: a) 0.20 L of 1.5 M KCl b) 0.160 L of 0.300 M HCl c) 0.20 L of 0.09 mol/L AgNO3 d) 250 mL of 3.1 mol/L BaCl2 a) 22 g b) 1.75 g c) 3 g
d) 0.16 kg
4.Give the molarity of a solution containing 10 g of each solute in 2.5 L of solution: a)H2SO4 b)Ca(OH)2 a) 0.041 mol/L
b) 0.054 mol/L
A Project in Fourth Grading Period in Advanced Chemistry
Submitted to: Mr. Dexter C. Necor Chemistry Teacher Submitted by: Irish Joy L. Pausal Pauline Raisa Jugar Kris Xyrille Escuadra Richie Cervantes