topic 8 acids and alkalis Flashcards Preview

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Flashcards in topic 8 acids and alkalis Deck (26):

what do these hazard symbols mean?

Q image thumb

A image thumb

what ion is present in all acids?



what ion is present in all alkalis?



what pH is acidic?

below 7


what pH is neutral?



what pH is alkali?

above 7 and below 14


what does acidic, neutral and alkaline look like on these common indicators?

litmus paper

methyl orange


                               acidic           neutral      alkaline

litmus paper          red                purple       blue

methyl orange       red                yellow       yellow

phenolphthalein    colourless   colourless    pink


what is the link between pH and the concentration of ions?

a very low pH means that there are lots of H+ ions e.g. HCL, in which half of the acid consists of H+ ions.

a pH of 7 means there are no H+ or OH- ions 

a very high pH means there are a lot of OH- ions in the alkali


what does stron/weak mean in terms of acids and alkalis?

a strong acid/alkali has a lot of H+/OH- ions present in the chemical, the molecules fully dissociate

weak means there are not many of these ions present in the chemical, the molecules dont fully dissociate


what does dilute/concentrated mean in terms of solute in a soltion?

a dilute solution means that there is not much solute for every bit of solvent and concentrated means there is a lot of solute for every bit of solvent


describe how a base reacts in a neutralisation reaction

bases, which consist of a + metal ion and an O2- ion, cancles out the charge of the H+ions by making water(2H++O2 > H2O) and the metal ion reacts with the nonmetal ion in the acid to form a salt


what are the steps in preparing a soluble salt from an acid and an insoluble salt

hav the acid in a beaker and keep adding and sturing in the insoluble reactant untill there is exess on the top which wont react, filter the solution to remove the exess reactant, evapourate off the water from the solution, you have salt


why do you use an exess of insoluble reactant when preparing a soluble salt?

when all of the acid has reacted, you will have a solution of salt dissolved in water. the insoluble salt cannot reaqct with the solution and wont dissolve, so can be easily filtered out to leave just the solution of water and salt


what is the difference between an alkali and a base?

an alkali is a soluble base

/a base is an insoluble alkali


acid + alkali >?

water + salt


acid + metal > ?

salt + hydrogen


acid + carbonate > ?

salt + water + carbon dioxide


acid + base > ?

salt + water


why is titration used to prepare a soluble salt from an acid and an alkali?

because it is very accurate and you end up with alot less exess acid or alkali left over in the final solution


how do you carry out an acid-alkali titration

using a pipette filler and a graduated glasspipette, measure out a known amount(say 100ml) of the acid and put it into a conical flask. Then fill the buret with the alkali, slowly add the alkali to the conical flask untill the solution is nutral. you can redo this many times to get a more accurate measurment.



what is the test for hydrogen gas?

lit splint, goes po


the test for carbon dioxide?

bubble it through lime water, it should go cloudy and white


what are the rules of solubility?

all common sodium, potassium and ammonium salts are soluble

all nitrates are soluble

most chlorides are soluble, except silver and lead

most sulphates are soluble, except lead, barium and calcium

most carbonated and hydroxides are insoluble, except sodium, potassium and ammonium



What is a precipitation reaction?

When 2 solution( in this case a salt dissolved in water) react to form an insoluble salt


What is the precipitate?

The precipitate is the insoluble salt formed from a precipitation reaction