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What is an acidic solution?
A solution with a pH less than 7
the lower the pH the stronger the acid
What is an alkaline solution?
A solution with a pH more than 7
the higher the pH, the stronger the alkali
an alkali is a base dissolved in water
What is the pH of a neutral solution?
pH 7
What ions do acids contain?
Hydrogen ions, H+
What ions do alkalis contain?
Hydroxide ions, OH-
What is a strong acid?
An acid which completely dissociates to release H+ ions in an aqueous solution
What is a weak acid?
An acid which partially dissociates to release H+ ions in aqueous solutions
What is a strong base?
A base which completely dissociates to release OH- ions in an aqueous solution
What is a weak base?
A base which partially dissociates to release OH- ions in an aqueous solution
What is the product formed when a metal is added to dilute acid?
Acid + Metal —> Salt + hydrogen
What would you see when observing an acid and metal reaction?
The hydrogen causes bubbling during the reaction- exothermic reaction
The more reactive the metal, the faster the reaction is resulting in more bubbling and a bigger temperature rise
What are the 3 neutralisation reactions of dilute acids?
• acid + alkali (metal hydroxide) —> salt + water
• acid + base (metal oxide) —> salt+ water
• acid + metal carbonate —> salt + water + carbon dioxide
What would u see when observing an acid and metal carbonate reaction?
The carbon dioxide causes bubbling during the reaction- reaction is exothermic
What is neutralisation?
Happens when an acid and alkali cancel eachother out- reaction always produces a salt and water
the H+ ions from the acid react with the OH- ions from the alkali to form water
How are crystals of insoluble salts prepared?
made when 2 soluble salts react in a precipitation reaction
Stage 1) mixing- two soluble salt solutions
Stage 2) filtration- the insoluble precipitate is separated from the mixture by filtration. The precipitate stays behind in the filter paper, while the solution passes through
Stage 3) washing and drying- water cannot dissolve the precipitate (it is insoluble) but it can wash off any remaining impurities. The filter paper is then removed, opened out and the precipitate dried in oven
How is a salt from an alkaline soluble carbonate prepared?
An alkali is a soluble base. A titration is used to produce a salt from an acid and alkali
1) measure exactly 25 of an alkali into a flask
2) add a few drops of indicator to the flask
3) place flask onto a white tile
4) fill burete with acid
5) slowly add acid from burete to the alkali until the indicator changes colour- endpoint of reaction
6) record the volume of acid added to the flask
7) repeat steps 1-6 without using indicator and adding the same volume of acid from the burete
• the salt crystals are collected by evaporation
How is a salt from a metal or insoluble base/ carbonate prepared?
Stage 1) excess metal/ base/ carbonate is added to the acid to make sure all the acid has been reacted and been used up. Heating and stirring helps the process. For metal and metal carbonates, the fizzing stops when all the acid has been used up
Stage 2) the mixture is filtered using a filter funnel and filter paper. The excess solid remains in the filter paper. The salt solution passes through into the evaporating duct.
Stage 3) the salt crystals are collected from the solution by evaporation. The solution is heated to evaporate to the water. The size of the crystals depend on the rate of evaporation
What are the names of salts formed from hydrochloric acid, nitric acid and sulfuric acid?
• hydrochloric acid produces chlorides
• nitric acid produces nitrates
• sulfuric acid produces sulfates
What is the test for sulfate ions?
• first add dilute hydrochloric acid, followed by barium chloride solution
• a white percipiate will from if sulfate ions are present in the solution
What is a titration calculation?
The volumes of acid and alkali solutions that react with eachother they can be measured by titrations using a suitable indicator
How do you calculate the concentration of a solution?
Concentration = mol/ volume
What does the concentration of an acid/ base refer to?
The amount of substance present- the number of moles that acid/ base in solution
What does the strength of an acid/base refer to?
To the degree of ionisation of the acid or base- how readily the acid releases H+ ions or how readily the base releases OH- ions
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