Chapter 11 - Acid & Base Reactions In Water

Common Acids

Hydrochloric Acid - Stomach Acid (Strong)

Sulfuric Acid - In car batteries (strong)

Ethanoic Acid - Batteries, fertilizers (strong)

Carbonic Acid - Carbonated Drinks (weak)

Phosphoric Acid - Fertilizers, drinks (weak)

Citric Acid - In citrus fruits (weak)

Ascorbic Acid - In citrus fruits (weak)

Common Bases

Sodium hydroxide - Oven cleaners (strong)

Ammonia - Fertilisers, explosives (weak)

Calcium hyrdoxide - Cement and mortar (strong)

Magnesium Hydroxide - For acid reflux (strong)

Sodium hydroxide - Powder, glass (strong)

Alkalis

Soluble/aqueous bases

Properties Of Acids

Turns litmus paper red

Tend to be corrosive

Taste Sour

Reacts With Bases

Solutions have low pH

Solution conducts an electrical current

Properties Of Bases

Turns litmus paper blue

Caustic, Slippery

Taste bitter

Reacts with acids

Solutions have pH

Solution conducts electrical current

Litmus Test

Robert Boyle deduced acids based on:

Taste

Action as solvents

How they change the color of vegetable extracts

Soluble bases (alkalis) could reverse the effect of acids

Antoine Lavoisier’s Suggestion

Acid properties due to Prescence of oxygen

Sir Humphrey David’s Discovery

Acidic properties are associated with hydrogen

Lime Water Test

Bronsted-Lowry Theory Of Acids and Bases

When substance donates (H⁺) proton - acid

When substance receives (H⁺) proton - base

Conjugate Acid Pairs

Amphiprotic Substances

Substance can receive or donate an electron - must have at least on hydrogen proton

Monoprotic Substances

Can have only one hydrogen that can be donated (eg.HCI or H₂0)

Polyprotic Acids

Acids that can donate more than one hydrogen atom

Don’t donate all protons at once

Donate protons in steps

Ionization Energy Across Steps

Harder to loose hydrogen protons as steps increase, due to the increase of electrostatic attraction.

Triprotic Acids

Have 3 protons that can be donated (done in three steps)

Diprotic Acids

Have 2 protons (done through 2 steps)

Water in all ionisation reactions

Water is a reactant in all ionization reactions

Why do Amphiprotic substances have a double reversible arrow

They can behave as either a base or an acid meaning that the reaction can happen in both ways.

Why must Hydrogen be next to a highly electronegative atom to be donated?

It creates a partial positive charge

Enables it to be transferred as a proton easily.

e.g. only a bond with O-H can be donated with acids such as CH₃COOH (acidic proton)

What is strength of a acid or base measured by?

By its ability to donate or accept protons

Dissolving into water

Strong acids completely ionize in water

Weak acids partially ionize in water

Weak acids

HCI

H₂S0₄

HN0₃

Strong Acids

CH₃C00H

H₂C0₃

H₃PO₄

Strong Bases

NaOH

KOH

Ca(OH)₂

Weak Bases

NH₃

What is concentration?

Measuring “solute” to “solvent” ration

Solute - Solvent ratio low?

Less solute

More solvent

Diluted solution

Solute - Solvent ratio high?

More solute

Less solvent

Concentrated solution

Acid & Base relationship with conjugates

Stronger the acid - weaker the conjugate base

Stronger the base - weaker the conjugate acid

Neutralization Reactions

Acid + metal hydroxide ——- Salt + water

Acid + bicarbonate ——- Salt + C0₂ + H₂0

Acid + metal carbonate —— Salt + H₂0 +C0₂

Acid + metal hydrogen carbonate —- Salt + H₂0 + C0₂

Acid + Reactive Metal ————- Salt + Hydrogen

Neutralization (real life)

Sting of bee (methanoic / formic acid) neutralized by ammonia or lime water

venom of wasp is alkaline - ethanoic acid can be used to treat it

Stomach acid treated with antacid (milk or magnesia)

Dissassociation

Ionic compounds seperate into ions

Water in a reaction

Weak acid and base

Only a small amount reacts

What does “M” stand for?

Concentration of moles per litre

Acidity of water at 25 degrees

[H₃0⁺]=[OH^-]=10^-7M

Hydronium = 10^-7M

Hydroxide = 10^-7M

They both multiply up to 10^-14M (half-half)

Acid Ionisation

[H₃0⁺] > 10^-7M - more hydronium ions than hydroxide ions make the solution more acidic

Base Ionisation

[OH^-] > 10^-7M - more hydroxide ions than hydronium ions make the solution more basic

Neutral

[H₃0] = [OH^-] - Both have 10^-7M

Measuring of acidity

pH = -log₁₀[H₃0⁺]

[H₃0⁺] = 10^-pH

Notes on pH

pH decreases as [H₃0⁺] increases (more hydronium = more acidic)

Indicators

Litmus - purple dye from lichen plant

Rose petals, blackberry, red cabbage - organic indicators

Converting to moles and finding concentration

n=m/n

C = n/v

n= moles

v = volume

c = concentration

Ocean acidity

Increase in C0₂ in atmosphere increases ocean acidity

Steps of CO₂ entering water

Why Is Ocean Acidity Bad

Krill eggs won’t hatch at lower pH (high acidity)

Stops food chain

Stops calcification for coverings of sea animals (decalcification) - acidity in sea water

Impact of Ocean Acidity On Humans

Social, Economic Impacts

Reduce sea life in water

Destroy coastal reefs - reduce tourism and increases erosion on land