2.2 Acids, Bases and Salts Flashcards by Rowan Bailey-Lear

What does the pH scale measure?

The concentration of hydrogen irons in the substance

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What do acids contain?

Hydrogen H+ ions

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Lower pH, stronger acid 🟰

High concentration of H+ ions
Lower pH, stronger acid

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What do alkalis contain?

Hydroxide ions, OH-

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Higher pH, stronger alkali 🟰

Higher concentration of OH- ions
Higher pH, stronger alkali

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Strong acids, what numbers in pH scale

Lower numbers

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Strong alkali is what numbers in pH scale

Higher numbers

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What do acids produce when they dissolve in water?

Hydrogen ions
HCl (aq) ➡️ H+ ➕Cl-

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What makes an acid a strong acid

Nearly all of the hydrogen atoms form H+ ions when dissolved in water
Fully dissociate (ionise)

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What is a base

Chemically opposite to an acid

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What is an alkali

A base that dissolved in water

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What do alkalis do when dissolved in water

Produce hydroxide ions OH-

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Why is ethanoic acid a weak acid for

Only1% of the H molecules form H+ ions When dissolved in water - partially dissociate/ionise

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Why is HCl a strong acid

Nearly all of the hydrogen atoms form H+ ions when dissolved in water
Fully dissociate/ionise

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What is a dilute acid

More water molecules mixed with the H+

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Concentrated acid

Fewer water molecules mixed with the H+ ions

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Strong acids react more quickly or slowly than weak acids

More quickly

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What do acids react with to form salts

Metals
Bases
Carbonates

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Réaction of acid ➕ metal- products
Example

Acid➕metal➡️salt➕hydrogen
Hydrochloric acid ➕ zinc➡️zinc chloride➕hydrogen

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What will you see in a reaction with a more reactive metal

Faster reaction
More bubbling
Bigger temperature rise

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What is a neutralisation reaction

Reaction of an acid with a base or alkali

What do neutralisation reactions always produce

Salt ➕ water 💦

Ionic equation for neutralisation reaction

H+ (aq) ➕ OH- ➡️ H2O
The other ions make the salt
HCl(aq)➕NaOH➡️NaCl➕H2O

What forms when **carbonates ** react with acids

Salt 🧂
Water 💦
Carbon dioxide 🫧

Reaction of acid and carbonate equation and example

Acid ➕ carbonate ➡️ salt ➕ water ➕ carbon dioxide 2HCl(aq)➕CaCO3(s)➡️CaCl2(aq)➕H2O➕CO2

Reactions of acids with metals bases and carbonates are all…

Exothermic

Testing for carbonates

React with an acid Test the gas given off is carbon dioxide-pass through limewater, limewater should go cloudy

Testing for acids

React with a carbonate Test the gas given off is carbon dioxide-pass through limewater, limewater should go cloudy

Test for a sulfate

React a **solution of the sulfate** with a **solution of barium chloride** ***white precipitate*** of barium sulfate is formed

Word and chemical equation for reacting (sodium) sulfate with barium chloride- test for a sulfate

Sodium sulfate ➕barium chloride➡️sodium chloride ➕ barium sulfate Na2SO4(aq)➕BaCl2(aq)➡️2NaCl(aq)➕BaSO4(s)

Ion equation for reacting (sodium) sulfate with barium chloride- test for a sulfate

Ba2+(aq)➕SO4 2-(aq)➡️BaSO4(s)

How can solid insoluble salts be prepared from soluble salt solutions like the ones used in the test for a sulfate

Filtration - insoluble salt is trapped by filter paper; the soluble salt solution passes through - the trapped insoluble salt is washed with distilled water, dried then scraped off filter paper

What do acids react with to form salts

Metals bases and carbonates

Preparation of a salt from a metal/insoluble base/carbonate and acid steps

1. Excess metal/base/carbonate is added to ensure all acid has reacted (Ms&cs- Fizzing stops here) 2. The mixture is filtered to remove excess solid 3. Salt crystals are collected from solution by evaporation

How fast to evaporate water if you want large crystals

Evaporate water slowly

How fast to evaporate water if you want large crystals

Evaporate 2/3 water quickly, then Allow to crystallise naturally

Naming salts from hydrochloric acid Nitric acid Sulfuric acid

(Metal/base/carbonate) chloride (Metal/base/carbonate) nitrate (Metal/base/carbonate) sulfate

Hydrochloric acid ➕zinc ➡️

Zinc chloride ➕water

Nitric acid ➕sodium carbonate

Sodium nitrate ➕water➕carbon dioxide

What is preparation of a salt from an alkali/soluble carbonate also known as

Titration

What is titration used for How

To produce a salt from an acid and alkali An acid is added to an alkali

When is the endpoint of a titration reaction

When the alkali/acid has been neutralised It has turned into a salt ➕ water

How are the salt crystals collected from titration

Evaporation

Titration steps

1. Measure (25cm3) of alkali into a conical flask using a pipette 2. Add a few drops of indicator 3. Fill the burette with acid 4. Slowly add the acid from the burette (dropwise) to the alkali until the indicator changed colour Record the volume of acid added to the flask

Equation to find Concentration in mol dm3

Mass/Mr✖️1000/volume Moles✖️1000/volume

Equation to find moles of solution using concentration and volume

Moles 🟰 concentration/1000✖️volume

Volume equation

Moles✖️1000/conc

1dm3 is how many cm3

1000 cm3

Example of 1:1 mole ratio

NaCl➕NaOH

Example of 2:1 mole ratio

**2**NaOH➕H2SO4