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Flashcards in Acids & Alkalis Deck (87):
1

Neutralisation

When an acid reacts with a alkali to produce a neutral solution of a salt and water

2

Indicator and examples

Something that changes colour due to a change in pH
E.g. Litmus, methyl orange, phenolphthalein

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Hydrochloric acid formula

HCl

4

Sulfuric acid formula

H2SO4

5

Nitric acid formula

HNO3

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All acids contain… The more concentrated the H+ ions…

All acids contain hydrogen atoms. When acids dissolve in water they form H+ ions. Therefore the pH of the acid will be lower

7

aq

Aqueous solution = dissolved in water

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All alkaline solutions contain… the more concentrated the OH- ions…

Contain OH- ions (hydroxide ions). The higher the pH of the alkali

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Concentration def

How many particles are dissolved in a given volume of liquid

10

Strength of an acid/alkali is determined by

Concentration, ability to donate hydrogen (protons) - more protons mean more dangerous means reactive

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High concentration means

Weak acid - partially dissociate

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Low concentration means

Strong acid - completely dissociate

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More hydrogen ions (protons) do…

More damage

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Work out concentration

Amount dissolved (g) / volume (dm3)

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1dm3

1000cm3
1l

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By increasing volume, the concentration

Decreases

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Mole

6.02x10^23

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Strong acid

Higher concentration of H+ ions and ability to donate protons

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Increase pH

Decrease concentration of hydrogen ions

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Base + acid --->

Salt + water

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pH probe attached to a pH meter

More accurate than universal indicator as it gives a numerical value

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Which ion is produced by an acid in aqueous solution

H+

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Ethanoic/Acetic acid formula

CH3COOH

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Citric acid formula

C6H8O7

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Carbonic acid formula

H2CO3

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Strong (good proton donors) acids to weak acids

Sulphuric, hydrochloric, nitric, citric, ethanoic, carbonic

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Dissociate

Breaking down of hydrogen ions and separating of anions

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Dynamic equilibrium

Forward and back at the same rate

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Tip for doing ionic equations

Start with the H+ ions first and don't forget about group ions and their charges

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SO4 charge

2-

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NO3 charge

1-

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CO3 charge

2-

33

Partially dissociate citric acid

3H+ + C6H5O7 3-

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Bases end in

Oxides, hydroxides, carbonates

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Alkali is a

Soluble base

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Concentrated vs dilute

More acid molecules per cm3 vs less

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Anhydrous solution

Water is driven out

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Base is

Any chemical that neutralises acids to make a salt and water only

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Sodium hydroxide formula

NaOH

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Potassium hydroxide formula

KOH

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Calcium hydroxide formula

Ca(OH)2

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Lithium hydroxide

LiOH

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Strong acids ( in terms of ions)

Strong completely dissociate into ions in solutions

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Weak acids (in terms of ions)

Partly break up into ions

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A concentrated solution

Contains lots of solute compared to the volume of solvent

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Dilute solution

Contains small amounts of solute compared to the volume of solvent

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Safety when making copper sulfate

Eye protection e.g. goggles, copper oxide is harmful especially when in eyes and scratch then, sulphuric acid is irritant

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How to make copper sulfate

Pour 20cm3 of dilute sulphuric acid into the conical flask. Warm the acid to 50°C using a water bath. Use a spatula to add a little copper oxide to the acid and stir using a glass rod. Keep repeating until all acid has reacted. Filter mixture and transfer to evaporating dish. Heat mixture over water bath until crystals start to form. Then leave in sun to evaporate water

49

Titration

When an acid is added from a burette to a fixed volume of alkali in a comical flask to obtain a neutral solution

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Burette

A tall piece of glassware used to release small drops of liquid to obtain an accurate volume to neutralise a solution

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Titration experiment

Use a pipette to measure the alkali. Use single indicators such as phenolphthalein or methyl orange as they have obvious colour changes to give a sharper endpoint. Use a white tile to make the colour change easier to see

52

When to use methyl orange and colour change

Strong acid + weak alkali (turns red in acid and yellow/orange in alkali)

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When to use phenolphthalein and colour change

Weak acid and strong alkali (turns colourless in acid and pink in alkali)

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Safety precaution with titration experiment

Fill burette below eye level. It can spill into your eyes and cause harm

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Concentration formula in terms of moles

Number of moles divided by volume

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If the concentration of hydrogen ions increases by a factor of 10, the pH…

Decreases by 1

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What happens during neutralisation

Hydrogen ions in the acid combine with oxide ions to form water. This removes the hydrogen ions and so the pH increases by becoming more neutral. The salts are produced by replacing the hydrogen ions with metal ions

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Ionic equation for hydrochloric acid

HCl --> H+ + Cl-

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Ionic equation for sulphuric acid

H2SO4 --> 2H+ + SO4 2-

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Ionic equation for nitric acid

HNO3 --> H+ + NO3-

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Ionic equation for ethanoic acid

CH3COOH H+ + CH3COO-

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Ionic equation for calcium hydroxide

Ca(OH)2 --> Ca2+ + 2OH-

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How to make soluble salt that isn't contaminated

Use a pH meter to check its neutral

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Titre

Initial volume - final reading

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Titration experiment

Tie long hair back and put on goggles. Measure using a pipette the alkali into the conical flask and add phenol. Place white tile under flask. Fill burette and remove the funnel. Add initial reading to table measuring under meniscus. Add acid slowly and swirl gently. Once colour change is permanent record final reading. Note the titre reading

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What observations can be seen during a reaction between an acid and a metal

Fizzing and dissolving

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What is produced from reacting metal and acid together

Metal + acid --> salt + hydrogen

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How to test for hydrogen

Squeaky pop test. A lot splint will go out and make a popping sound in the presence of hydrogen gas

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Carbonate + acid

--> salt + water + carbon dioxide

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What observation can be seen when reacting metal carbonates with acids

Dissolving

71

Test for carbon dioxide

Clear limewater goes cloudy when carbon dioxide is added

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Metal reactivity series

Potassium Sodium Calcium Magnesium Aluminium (carbon) Zinc Iron Tin Lithium Copper Silver Gold Platinum

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OILRIG

Oxidation is Loss, Reduction is Gain

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Half equation for metal

E.g. Na --> Na+ + e-

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Half equation for non metal

Cl + e- --> Cl-

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(Solubility) most chlorides

Soluble

77

(Solubility) most sulfates

Soluble

78

(Solubility) Most carbonates

Insoluble

79

(Solubility) Most hydroxides

Insoluble

80

(Solubility) all nitrates

Soluble

81

Silver and lead chloride (Solubility)

Insoluble

82

Lead, barium, calcium sulfate (Solubility)

Insoluble

83

Sodium, potassium, ammonium carbonates (Solubility)

Soluble

84

Sodium, potassium, ammonium hydroxide (Solubility)

Soluble

85

Solubility def

A measure of how much of a substance will dissolve in a litre of water

86

Precipitate reaction

2 aqueous solutions make a solid product

87

Precipitate experiment

Mix two aqueous solutions together in equal amounts to make a neutral homogeneous solution. Pour through filter paper onto a conical flask. Keep the filtrate. Wash with distilled water to dissolve soluble ions to make it pure. Leave to dry and evaporate water