A mixture of different plant indicators which operate across a broad pH range and is useful for estimating the pH of an unknown solution
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Describe the use of universal indicator to measure the approximate pH value of an aqueous solution
A few drops are added to the solution and the colour is matched with a colour chart which indicates the pH that matches with specific colours
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When acids are added to water ...?
they form positively charged hydrogen ions (H+)
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What makes a solution acidic?
the presence of H+ ions
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When alkalis are added to water ...?
they form negative hydroxide ions (OH-)
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What makes a solution alkali?
the presence of OH- ions
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What is the pH scale?
a numerical scale which is used to show how acidic or alkaline a solution is. In other words, it is a measure of the amount of ions present in solution
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When does a neutralisation reaction occur?
When an acid reacts with an alkali
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What happens when an acid reacts in a neutralisation reaction with an alkali?
The H+ ions react with the OH- ions to produce water
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Titrations
A method of analysing the concentration of solutions Can be used to prepare salts
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How to perform a titration
(See method in booklet 2.6)
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Soluble ionic compounds
Compounds of sodium, potassium and ammonium All nitrates Nearly all chlorides Nearly all sulphates Sodium, Potassium, and Ammonium carbonates Sodium Potassium, and calcium hydroxides
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Insoluble Ionic compounds
Silver and lead (II) chlorides Barium, calcium, and lead (II) sulphates Nearly all carbonates Nearly all hydroxides
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Salt
A salt is a substance formed from an acid where the H+ ions in the acid are replaced by either metal ions or ammonium ions Ionic compounds
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Acids
Proton donors as they ionise in solution producing protons, H+ ions These H+ ions make the aqueous solution acidic Acids release H+ ions when dissolved in water
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Alkalis are ________ bases
soluble
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Bases (Alkalis)
Bases (alkalis) are proton acceptors as they ionise in solution producing OH- ions which can accept protons These OH- ions make the aqueous solution alkaline Alkalis dissolve in water to release OH- ions
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A proton is the same as ...? And why?
a H+ ions because a hydrogen atoms only contains one proton and one electron. When a hydrogen ion is formed, the electron is lost and a proton is left behind
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General equation for metals reacting with acid
metal + acid -> salt + hydrogen
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Which metals will react with dilute acids?
only metals above hydrogen
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Reaction of acids with bases makes ...?
Soluble salts
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General equation in all acid-base neutralisation reactions
acid + base -> salt + water
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Which substances act as bases?
Metal oxides, metal hydroxides and ammonium
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Reactions of acids with metal carbonates make ...?
Soluble salts
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General equation for the acids reacting with metal carbonates
metal carbonate + acid -> salt + carbon dioxide + water
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Base
Substances which can neutralise an acid, forming a salt and water
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Bases are usually ...?
Oxides, hydroxides or carbonates of metals
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Describe an experiment to prepare a pure, dry sample of a soluble salt, starting from an insoluble reactant
(See method in booklet 2.7)
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Solubility
The amount (mass) of solute needed for 100g of solvent to maintain a saturated solution at a certain temperature
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Flashcard (85)