Introduction 5405280
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Many ways to classify compounds Are they ionic or covalent? A common method is to separate into ACIDS and BASES. INTRODUCTION. We see, use, and eat acids everyday Sour grapefruit Tart taste of carbonated drinks Tangy taste of salad dressing. acids.

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INTRODUCTION

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Introduction

  • Many ways to classify compounds

    • Are they ionic or covalent?

  • A common method is to separate into ACIDS and BASES

INTRODUCTION


Acids

  • We see, use, and eat acids everyday

    • Sour grapefruit

    • Tart taste of carbonated drinks

    • Tangy taste of salad dressing

acids


Introduction 5405280

Acidic juices are added to food to improve tasteand help absorb nutrients

Stomach acid helps us digest food


Acids 2

  • Have corrosive properties

    • Acid rain can dissolve caves, buildings, and statues

    • Used to remove rust and purify/process metals

Acids - 2


Bases

  • Bitter tasting compounds with a slippery feel

  • Includes many cleaning products

    • Soap

    • Over cleaner

  • Some medical drugs are

    bases  lidocaine

  • We eat some basic foods

     eggs and baking soda

  • Also known as alkaline

bases


Safety

  • Some acids and bases can be corrosive

    • Can burn throat or stomach if swallowed

    • Can burn skin or eyes on contact

  • NEVER attempt to identify an acid or base in the lab by taste or feel!

SAFETY


Ph scale

pH Scale: a number scale for measuring how acidic or how basic a solution is

Acids: have a pH of less than 7 when dissolved in water

Bases: have a pH of more than 7 when dissolved in water

Neutral: has a pH of 7 (not an acid or a base)

pH Scale


Ph of common substances

  • The more acidic a solution is, the lower the pH

    • Lemon juice – pH 2

    • Tomato juice – pH 4

  • The more basic(oralkaline) a solution is, the higher the pH

    • Think of alkaline Earth metals  includes Ca and Mg which are basic when they react in water

    • Soap– pH 10

    • Oven Cleaner – pH 13

pH of Common Substances


Introduction 5405280

  • Neutral substances are

    neither acidic nor basic

    • Pure Water – pH 7

    • Saliva – pH 6.5-7.4

    • Human blood – pH of 7.3

      to 7.5 (slightly basic)


Using the ph scale

1 unit of change represent a 10 times change in the degree of acidity/basicity

Q: What is the increase in acidity if the pH drops from 6 to 4?

A: A 2 unit drop is a 10² or 100 times increase in acidity!

IMPACT: Even a small increase in acidity harms coral reefs and organisms that require a specific pH level to survive (ex. organisms that use calcium to make their shells)

Using the pH Scale


Ph indicators

Many common acids and bases form colourless solutions (look like water)

pH Indicators: chemicals that change colour depending on the pH of the solution they’re placed in

So what are some common indicators you could use?

pH Indicators


1 litmus paper

  • Litmus is extracted from lichens and dried onto thin paper strips

  • 2 forms: RED and BLUE

    • When BLUE litmus paper is placed in an acidic solution the paper will turn red

    • When RED litmus paper is placed in a basic solution it will turn blue

    • Can use both to tell if something is neutral  BLUE will stay blue and RED will stay red

      HELPFUL HINT!

  • BAR = Blue + Acid  Red

1. Litmus Paper


2 universal indicator

Contains many indicators that turn different colours depending on a solution’s pH

Uses a digital pH meter or pH computer probe to measure the electrical property of the solution, determining its pH

2. Universal Indicator


3 other ph indicators

  • Not all indicator change colour at pH 7 like litmus

  • Phenolphthalein: colourless in acidic/slightly basic solutions but turns PINK in moderately-highly basic solutions

  • Bromothymol blue, indigo carmine, methyl orange, and methyl red  all named after their colour change

    • Methyl orange: changes from red to yellow over pH of 3.2-4.4

3. Other pH Indicators


Acids1

Can sometimes identify acids by their chemical formulas

Many compounds (HCl) take on acid properties after mixing with water

Ex.: HCl dissolved in water is written as HCl (aq), where (aq) means “aqueous” or “dissolved in water to make a solution

acidS


Acids 21

  • Chemical formulas usually have an “H” (hydrogen) on the left side of the formula  HCl (aq)

  • In acids that contain CARBON, “H” may be written on the right side  CH₃COOH (aq)

  • If no state of matter is given, the name may be given beginning with “Hydrogen”

    • Hydrogen chloride

  • If the acid is aqueous (ex. HCl (aq)), a different name is used that ends in “-ic acid”

    • Hydrochloric acid

Acids - 2


Naming acids

  • Basic pattern when “O” (oxygen) is present

    • Names that begin in “hydrogen” and end in “-ate” are changed by dropping “hydrogen” from the name and changing the suffix to “-ic acid”

      Ex.: Hydrogen carbonate  carbonic acid

      • Names that begin with “hydrogen” and end with “-ite” change by dropping the hydrogen and replacing the suffix with “-ous acid”

        Ex.: Hydrogen sulphite  sulphurous acid

Naming Acids


Introduction 5405280

  • Basic pattern when “O” (oxygen) is absent

    • Combine the 2 element names, then replace the ending with “-ic acid”

  • Ex.: hydrogen fluoride  hydrofluoric acid

  • Ex.: hydrogen iodide  hydriodic acid


Introduction 5405280

  • The chemical formula of an acid usually starts with hydrogen (H).

    • Acids with a carbon usually have the C written first.

      • HCl(aq) = hydrochloric acid, HNO3(aq) = nitric acid, CH3COOH(aq) = acetic acid

  • Naming acids

    • Hydrogen + …-ide = hydro…ic acid

      • HF(aq) = hydrogen fluoride = hydrofluoric acid

    • Hydrogen + …-ate = …ic acid

      • H2CO3(aq) = hydrogen carbonate = carbonic acid

    • Hydrogen + …-ite = …ous acid

      • H2SO3(aq) = hydrogen sulphite = sulphurous acid


Bases1

  • Usually written with an “OH” on the right side of the formula

  • Some bases are much stronger than others

    • Magnesium hydroxide founds in antacids while sodium hydroxide is found in drain cleaner

  • Caustic: solutions made from highly reactive bases

Bases


Bases 2

  • Examples of common bases:

    • NaOH(aq)

    • Mg(OH)2(aq)

    • Ca(OH)2(aq)

    • NH4OH(aq)

Bases - 2


Production of ions

  • Acids and bases can conduct electricity because they

    release ions in solution.

    • Acids release hydrogen ions, H+

    • Bases release hydroxide ions OH–

  • The pH of a solution refers to the concentration of H+ (aq) ions it has.

  • Concentration of H+ ions refers to the number of H ions in a specific volume

Production of Ions


Introduction 5405280

  • Square brackets are used to signify concentration, [H+], [OH–]

    • High [H+] = low pH, very acidic

    • High [OH–] = high pH, very basic

  • A solution cannot have BOTH high [H+] and [OH–]; they cancel each other out and form water. This process is called neutralization.

  • H+ + OH– H2O


Introduction 5405280

  • Environmental Example:

    • After the mining of minerals, the remaining ground rock (tailings) are usually deposited in a tailings pond

    • The tailings can release acids, lowering the pH of the water and affecting the environment

    • Can counteract this problem by adding a base to raise the pH level back to normal


Properties of acids and bases

Properties of Acids and Bases


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