chemistry paper 1 acids/alkalis

Question 1

what do international symbols on chemicals show?

Answer 1

the hazards associated with handling those particular solutions and they indicate the precautions needed when handling them.

Question 2

what is an indicator?
how can the pH of a solution be found?
universal indicator?

Answer 2

substance that changes colour depending on the pH
using an indicator
is made from a mixture of different indicators and produces a range of colours depending on the pH

Question 3

polyatomic ions are formed…

Answer 3

when small groups of atoms held together by covalent bonds loose or gain electrons.

Question 4

what do acids and alkalis produce an excess of when dissolved in water?

Answer 4

acids - hydrogen ions (H+)
alkali - hydroxide ions (OH-)

Question 5

The higher the number of hydrogen ions in a certain volume….

the higher the concentration of hydroxide ions ..

Answer 5

the higher their concentration. The more acidic the solution and lower the pH.

the more alkaline the solution and the higher the pH

Question 6

concentrated solution
dilute solution

Answer 6

contain alot of dissolved solute per unit volume
contain a small amount of solute per unit volume

Question 7

more concentrated acids…

Answer 7

contain more hydrogen ions so they will react faster with eg. magnesium metal

Question 8

what does the pH of a solution measure? (acids)

Answer 8

the concentration of hydrogen (H+) ions

Question 9

what happnes with strong acids?

weak acids

Answer 9

their molecules dissociate completely into ions when dissolved in water, producing higher concs of H+ ions

don’t dissociate completely

Question 10

what is a base?

Answer 10

substances that neutralise acids to form a salt and water. All metal oxides are bases.

Question 11

what happens during neutralisation?

Answer 11

hydrogen ions in the acid combine with oxide ions to form WATER. This removes hydorgen ions so the pH will increase and become more neutral.

the SALT is produced by replacing hydrogen ions with metal ions.

Question 12

(1) The reaction between an acid and insoluble metal oxide ion…

Answer 12

can be used to prepare samples of different soluble salts

Question 13

(2) if if soluble salts are prepared from an acid and an
insoluble reactant why..

is excess of the reactant is added
the excess reactant removed
the solution remaining is only salt and wate

Answer 13

-to make sure all the acid is used up
-to mkae sure the prepared salt is pure
-so water can cyrstalise leaving just salt

Question 14

if a base can dissolve in water it makes it..

Answer 14

alkali

Question 15

in a neutralisation reaction H+ and OH- ions form water and the other ions..

Answer 15

stay in solution as ions of the dissolved salt

Question 16

how can you obtain dry soluble salts from its solution? (alkali)
why should it be neutral?

Answer 16

by crystallisation
otherwise youll contaminate the salt with an excess of one reactant

Question 17

what is used to obtain a neutral solution?
(mixing an acid and alkali in correct amounts)

Answer 17

titration

Question 18

how do you make pure dry saluble salt from alkali using titration

Answer 18

-carry out a titration
-note the volume of acid needed to neutralise the alkali
-use burette to add correct volume of acid without indicator
-evap water from solution formed

Question 19

what happens when acids react with SOME metals?

Answer 19

the metal atoms react with hydrogen ions to form metal ions and hydrogen molecules

metal + acid ——–salt + hydrogen

Question 20

what happens when acids react with metal carbonates?

Answer 20

they form a salt, water and carbon dioxide.

Question 21

test for carbon dioxide.

Answer 21

bubble the gas through limewater, the limewater turns milky if co2 is present

Question 22

test for hydrogen

Answer 22

Place a lighted splint in the tube of gas. (1)
If there is a squeaky pop, this proves that hydrogen
is present.

Question 23

what is a precipotation reaction?

Answer 23

soluble substances in solutions cause and insoluble precipitate to form.

Question 24

what substances are soluble in water?

Answer 24

-sodium potassium and ammonium salts, hydroxides and carobnates
-nitrates, most chlorides and sulphates

Question 25

what substances are insoluble?

Answer 25

silver, lead chlorides,
lead barium and calcium sulfates

Question 26

if both products are soluble in solution…
insoluble..

Answer 26

an insoluble precipitate will form.
precipate will form

Question 27

how do u prepare insoluble salts?

Answer 27

-mix solutions in beaker then filture mixture
-rinse beaker w lil distilled water, pour this through funnel
-remove filter paper containing precip and dry in warm oven