Solutions, Acids & Bases

Solutions, Acids & Bases
Unit 9

What is a solution? Solution – a mixture where the components are uniformly intermingled. Homogeneous Solutions are made up of a solvent and solute. Solute – substance that is dissolved Solvent – substance in which materials are dissolved in. The medium in which the solute is dissolved in.

Solution Composition The solubility of a solute is limited.
Saturated solution – contains as much solute as will dissolve at that temperature Unsaturated solution – has not reached the limit of solute that will dissolve Oversaturated solution – contains too much solute in which the rest of solute remains on the bottom

Supersaturated solution – occurs when a solution is saturated at an elevated temperature and then allowed to cool but all of the solid remains dissolved Contains more dissolved solid than a saturated solution at that temperature Unstable – adding a crystal causes precipitation

Amounts of substances can vary in different solutions.
Specify the amounts of solvent and solutes Qualitative measures of concentration concentrated – relatively large amount of solute dilute – relatively small amount of solute

B. Solution Composition: An Introduction
Which solution is more concentrated?

C. Factors Affecting the Rate of Dissolving
Surface area Stirring Temperature

Solubility Curves Graphs that illustrates how much of solute will dissolve at any given temperature.

Solubility Chart

Questions How many grams of KClO3 is diluted in water at 90 degrees?
How many grams of K2Cr2O7 is diluted in water at 60 degrees? How many grams of Pb(NO3)2 is diluted in water at 10 degrees? 70g of CaCl2 will dissolve at what temperature to form a saturated solution? 40g of NaCl will dissolve at what temperature to form a saturated solution? 90g of KNO3 will dissolve at what temperature to form a saturated solution? At 30 degrees, you dissolve 25 grams of KNO3 in water. How much more KNO3 can you add to make it a saturated solution? At 10 degrees, you dissolve 25 grams of NaNO3 in water. How much more NaNO3 can you add to make it a saturated solution? At 90 degrees, you dissolve 10 grams of KClO3 in water. How much more KClO3 can you add to make it a saturated solution? Which salt has solubility values that are least affected by temperature? At 75 degrees, I attempted to dissolve 50g of KCl. Is this a saturated, unsaturated, or supersaturated solution? At 40 degrees, I attempted to dissolve 50g of NaCl. Is this a saturated, unsaturated, or supersaturated solution? At 55 degrees, I attempted to dissolve 50g of Pb(NO3)2. Is this a saturated, unsaturated, or supersaturated solution?

B. Solution Composition: Molarity
Concentration of a solution is the amount of solute in a given volume of solution.

Consider both the amount of solute and the volume to find concentration.

Example Problem What is the concentration (or Molarity) of a solution that contains 432 mole NaCl in 3.0 L of water?

𝑚𝑜𝑙𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝐿𝑖𝑡𝑒𝑟𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 = 432 𝑚𝑜𝑙 𝑁𝑎𝐶𝑙 3.0 𝐿 𝐻 2 𝑂 = 144M

Example Problem What is the concentration of a solution that contains 11.2g of LiCl in a 0.50L solution? Make sure that you convert the grams to moles before you find the molarity.

First, convert the grams to moles.
11.2g LiCl 1 mol LiCl = mol LiCl 42.39g LiCl Use the moles to find the molarity. 0.264𝑚𝑜𝑙 𝐿𝑖𝐶𝑙 0.50𝐿 = 0.53M

To find the moles of solute in a given volume of solution of known molarity use the definition of molarity.

How many grams of HCl was mixed into a 3L of a 9M solution?
Remember that: 𝑚𝑜𝑙𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝐿 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 =𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 (𝑀)

What do we know? Concentration = 9M L of solution = 3 Mols of solute = ? 𝑚𝑜𝑙𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝐿 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 =𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 (𝑀)

𝑚𝑜𝑙𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝐿 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 =𝐶𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 (𝑀) 𝑚𝑜𝑙𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 3𝐿 =9𝑀 Solve for the moles of solute

𝑚𝑜𝑙𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 3𝐿 =9𝑀 Mols of solute = (9M)(3L) = 27 mols of HCl You need to convert the mols of HCl to grams of HCl. 27 mols HCl 34.46g HCl = g HCl 1 mol HCl

Practice Problems Calculate the molarity of a solution prepared by dissolving 11.5g of solid NaOH in enough water to make 1.50L of solution. 2. Calculate the molarity of a solution prepared by dissolving 1.56g of gaseous HCl into enough water to make L of solution.

Practice Problems 3. What is the volume of a 3.2M solution of H2SO4 in a 0.30 L beaker? 4. What is the mass (g) of a 1.2M solution of CaCO3 in a 0.50 L flask?

Dilution Water can be added to an aqueous solution to dilute the solution to a lower concentration. Only water is added in the dilution – the amount of solute is the same in both the original and final solution.

D. Dilution Diluting a solution
Transfer a measured amount of original solution to a flask containing some water. Add water to the flask to the mark (with swirling) and mix by inverting the flask.

D. Dilution We can use a simple equation can be used in order to correctly dilute a solution to any concentration M1V1 = M2V2 M1 = the molarity of the initial solution V1 = volume of the initial solution M2 = the molarity of the diluted solution V2 = volume of the diluted solution

Example Problem 1. Suppose we want to prepare 500. mL of 1.00 M acetic acid, HC2H3O2, from a 17.5M stock solution of acetic acid. What volume of the stock solution is required? M1V1 = M2V2 M1 = 17.5M V1 = ? M2 = 1.00M V2 = 500 mL (17.5)V1 = (1.00)(500) V1 = (1.00)(500) = 28.6mL

Practice Problems What volume of 16M sulfuric acid must be used to prepare 1.5L of a 0.10M H2SO4 solution? What is the concentration when you dilute 0.3L of 10M of HCl in to a .500L solution? What is the concentration of a 250mL solution that was used to make a 600mL solution of 2.5M of NaCl? 6M 6M

I. Introduction to Acids & Bases

A. Properties ACIDS BASES electrolytes  electrolytes sour taste
bitter taste turn litmus red turn litmus blue react with metals to form H2 gas slippery feel vinegar, milk, soda, apples, citrus fruits ammonia, lye, antacid, baking soda ChemASAP

Acids (Svante Arrhenius’ Definition)
Acids form hydrogen ions or hydronium ions when dissolved in water H+ H3O+

HCl + H2O  H3O+ + Cl– B. Definitions – +
Arrhenius - In aqueous solution… Acids form hydronium ions (H3O+) HCl + H2O  H3O+ + Cl– H Cl O – + acid

Common Acids HCl Hydrochloric H2SO4 Sulfuric HNO3 Nitric
H3PO4 Phosphoric H2CO3 Carbonic

Acid Nomenclature Binary Compound – compound consisting of 2 elements.
An acid binary compound consists of 2 elements in which one of them is ALWAYS hydrogen. HF HCl HBr

Acid Nomenclature To name acid binary compounds Add hydro- as a prefix
Use the root of the element and add –ic acid as a suffix

Acid Nomenclature HF Hydrofluoric acid HCl Hydrochloric acid H2S
Hydrosulfuric acid H3P Hydrophosphuric acid

Acid Nomenclature Writing the name from chemical formulas
Figure out the charge of the anion Hydrobromic acid – H+ and Br- Br has a negative 1 charge Add enough H+ until the compound is neutral

Acid Nomenclature Hydronitric acid H3N Hydrofluoric acid HF
Hydroselenic acid H2Se

Acid Nomenclature Acid polyatomic compounds
Remember polyatomic compounds are compounds that have a charge. When naming polyatomic acids… DO NOT USE HYDRO- as preffix Use either –ic acid or –ous acid

Acid Nomenclature H2SO4 – Sulfuric acid Add –ic ate—ic / ite—ous Rule
If the polyatomic ion ends with an –ate replace it with an –ic acid H2SO4 – SO4 is sulfate H2SO4 – Sulfuric acid Add –ic

Acid Nomenclature HNO2 – Nitrous acid Add -ous ate—ic / ite—ous Rule
If the polyatomic ion ends with an –ite then replace it with an –ous acid HNO2 – NO2 is nitrite HNO2 – Nitrous acid Add -ous

Example Problems H2SO3 H3PO4 HClO2 HC2H3O2 H2Cr2O7 H2CO3 HNO2
Sulfurous acid Phosphoric acid Chlorous acid Acetic acid Dichromic acid Carbonic acid Nitrous acid

Acid Nomenclature Writing the name from chemical formulas
Figure out the charge of the polyatomic ion Sulfuric acid – H+ and SO4-2 SO4 has a negative 2 charge Add enough H+ until the compound is neutral H2SO4

Example Problems Hypochlorous acid Perchloric acid Nitric acid
Permanganic acid Sulfurous acid HClO HClO4 HNO3 HMnO4 H2SO3

More Example Problems HF Hydrofluoric acid Hydrochloric acid H2Se HCl
Chromic acid HClO3 Chlorous acid HNO3 H3N Hydrofluoric acid HCl Hydroselenic acid H2CrO4 Chloric acid HClO2 Nitric acid Hydronitric acid

Bases (Arrhenius’ Definition)
Bases form hydroxide ions when dissolved in water OH-

NH3 + H2O  NH4+ + OH- B. Definitions – +
Arrhenius - In aqueous solution… Bases form hydroxide ions (OH-) NH3 + H2O  NH4+ + OH- H N O – + base

Common Bases NaOH Sodium Hydroxide NH4OH Ammonium Hydroxide
Ca(OH)2 Calcium Hydroxide

HCl + H2O  Cl– + H3O+ B. Definitions acid conjugate base base
Brønsted-Lowry Acids are proton (H+) donors. Bases are proton (H+) acceptors. HCl + H2O  Cl– + H3O+ acid conjugate base base conjugate acid

B. Definitions H2O + HNO3  H3O+ + NO3– B A CA CB

Amphoteric - can be an acid or a base.
B. Definitions NH3 + H2O  NH4+ + OH- B A CA CB Amphoteric - can be an acid or a base.

Polyprotic - an acid with more than one H+
B. Definitions Give the conjugate base for each of the following: HF H3PO4 H3O+ F - H2PO4- H2O Polyprotic - an acid with more than one H+

Br - HBr HSO4- H2SO4 CO32- HCO3- B. Definitions
Give the conjugate acid for each of the following: Br - HSO4- CO32- HBr H2SO4 HCO3-

C. Strength Strong Acid/Base 100% ionized in water strong electrolyte
- + HCl HNO3 H2SO4 HBr HI HClO4 NaOH KOH Ca(OH)2 Ba(OH)2

C. Strength Weak Acid/Base does not ionize completely weak electrolyte
- + HF CH3COOH H3PO4 H2CO3 HCN NH3

H2O + H2O H3O+ + OH- Kw = [H3O+][OH-] = 1.0  10-14
A. Ionization of Water At any one time water solution contains hydronium and hydroxide ions. H2O + H2O H3O+ + OH- Kw = [H3O+][OH-] = 1.0  10-14

A. Ionization of Water Find the hydroxide ion concentration of 3.0  10-2 M HCl. [H3O+][OH-] = 1.0  10-14 [3.0  10-2][OH-] = 1.0  10-14 [OH-] = 3.3  M Acidic or basic? Acidic

pouvoir hydrogène (Fr.)
B. pH Scale 14 7 INCREASING ACIDITY INCREASING BASICITY NEUTRAL pH = -log[H3O+] pouvoir hydrogène (Fr.) “hydrogen power”

pH of Common Substances
B. pH Scale pH of Common Substances

pH = -log[H3O+] pOH = -log[OH-] pH + pOH = 14
B. pH Scale Important Equations pH = -log[H3O+] pOH = -log[OH-] pH + pOH = 14

pH = -log[H3O+] pOH = -log[OH-] pH + pOH = 14
[H3O+] = concentration of the acid [OH-] = concentration of the base

The pH of sea water is about 7.8. What is the pOH?
What do we know? pH = 7.8 What are we trying to figure out? pOH = ? What equation should we use? pH + pOH = 14

6.2 The pH of sea water is about 7.8. What is the pOH? pH + pOH = 14
Solve for pOH pOH = 14 – 7.8 Calculate 6.2

B. pH Scale What is the pH of 0.050 M HNO3? pH = -log[H3O+]
Acidic or basic? Acidic

B. pH Scale What is the molarity of HBr in a solution that has a pOH of 9.6? pH + pOH = 14 pH = 14 pH = 4.4 pH = -log[H3O+] 4.4 = -log[H3O+] -4.4 = log[H3O+] [H3O+] = 4.0  10-5 M HBr Acidic

Example Problems 3.7 5.0 x 10-5 M 7.9 x 10-6 M 4.3 1.6
What is the pH of a substance that has a pOH of 10.3? What is the concentration of an acid that has the pH of 4.3? What is the concentration of a base that has the pH of 8.9? What is the pH of an substance with the [H3O+] concentration of 5.0 x 10-5 M? What is the pOH of a substance with the [H3O+] concentration of 4.2 x 10-13? 3.7 5.0 x 10-5 M 7.9 x 10-6 M 4.3 1.6

Titrations

A. Neutralization Chemical reaction between an acid and a base.
Products are a salt (ionic compound) and water.

ACID + BASE  SALT + WATER
A. Neutralization ACID + BASE  SALT + WATER HCl + NaOH  NaCl + H2O strong strong neutral HC2H3O2 + NaOH  NaC2H3O2 + H2O weak strong basic Salts can be neutral, acidic, or basic. Neutralization does not mean pH = 7.

B. Titration standard solution unknown solution Titration Analytical method in which a standard solution is used to determine the concentration of an unknown solution.

B. Titration Equivalence point (endpoint)
Point at which equal amounts of H3O+ and OH- have been added. Determined by… indicator color change dramatic change in pH

Solutions, Acids & Bases

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