Acids and Alkalis

Question 1

PH

Answer 1

a measure of how alkaline or acidic a substance is
0-14
low numbers = acid, high numbers = alkaline

Question 2

ways of measuring pH

Answer 2

Universal indicator
ph probe with meter
phenolphalien
methyl orange

Question 3

base

Answer 3

any substance with a PH greater than 7

Question 4

alkali

Answer 4

subgroup of bases that are soluble in water
forms OH- ions in water

Question 5

acid

Answer 5

any substance that forms an aqueous solution with a PH less than 7
forms H+ ions in water

Question 6

common acids

Answer 6

Hcl (hydrochloric acid)
H2SO4 (sulfuric acid)
HNO3 (nitric acid)

Question 7

titration

Answer 7

a technique where a solution of known concentration is used to determine the concentration of an unknown solution

Question 8

general equations for a neutralision reaction

Answer 8

metal oxide + acid –> salt + water (this is for an acid)
metal hydroxide + acid –> salt + water

Question 9

ionic equation for neutralisation reaction

Answer 9

e.g. H+ + OH- –> H2O
e.g. HCl + NaOH –> NaCl + H2O
if a substance is neutral, it will have a PH of 7

Question 10

ionic equation definition

Answer 10

reaction involving ions in a solution
anything that is made up of ions and is aqueous will break up into its ions in a solution

Question 11

spectator ions

Answer 11

ions that do not contribute in the equation

Question 12

how titration works

Answer 12

use a pipette and add some acid to a flask.

add a small amount of phenolphthalein indicator.

fill the burette with base and carefully drop some into the acid

when the colour changes, stop and record the volume

repeat several times and get an average.

Question 13

how can you make the titration test easier

Answer 13

we can add acid to the base slowly and take readings on a PH probe (gives exact PH values)
we can plot a graph against volume of acid added

Question 14

how can you make the titration test easier

Answer 14

we can add acid to the base slowly and take readings on a PH probe (gives exact PH values)
we can plot a graph against the volume of acid added

Question 15

equivalence point

Answer 15

point in titration at which the volume of acid added is just enough to neutralize the solution

Question 16

strong acids

Answer 16

dissociate completely
PH of 0-2
can have low concentrations

Question 17

weak acid

Answer 17

dissociate partially
PH of 3-6
can have high concentrations

Question 18

examples of weak acids

Answer 18

ethnoic acid, citric acid

Question 19

acid concentration

Answer 19

the mass of acid dissolved in a given volume of water
changing the concentration of an acid affects its PH

Question 20

equation for concentration

Answer 20

concentration = mass/volume

Question 21

dont confuse strength of an acid with concentration

Answer 21

just dont

Question 22

if an acid with a PH of 6 changes to a PH of 3, how much did the concentration change?

Answer 22

the H+ concentration has increased by a factor of 1000

Question 23

if an acid with a PH of 6 changes to a PH of 9, how much did the concentration change?

Answer 23

the H+ concentration has decreased by a factor of 1000

Question 24

other general equations that you have to know for the test

Answer 24

acid + metal –> salt + hydrogen
acid + metal carbonate –> salt + water + carbon dioxide

Question 25

all polyatomic ions to know

Answer 25

CO3^2- Cl- NO3- SO4^2-

Question 26

precipitation reaction

Answer 26

adding two soluble salts together to make insoluble salts

Question 27

soluble or insoluble: salts of Na, K and NH4 nitrates common chlorides common sulphates common carbonates and hydroxides

Answer 27

soluble or insoluble: soluble soluble soluble except silver and lead soluble except lead, barium and calcium insoluble except sodium, potassium and ammonium

Question 28

Acid strength

Answer 28

The amount of acid that dissociated (what portion of acid molecules ionised in water)

Question 29

colour of methyl orange in acid

Answer 29

red

Question 30

colour of methyl orange in alkali

Answer 30

yellow

Question 31

colour of phenolphelien in acid

Answer 31

colourless

Question 32

colour of phenolphthalein in alkali

Answer 32

pink

Question 33

explain the steps in a soluble salt from insoluble base experiment

Answer 33

pour a dilute acid into a flask heat flask add base, e.g. copper oxide into the flask heat speeds up the rate of reaction repeat last step until base stops reacting with acid this is done to ensure the mixture has reacted completely leave to cool filter mixture into a beaker and pour into an evaporating basin place evap basin on top of a beaker with water, the beaker with water will evaporate which will in turn heat the evap basin heat until small amount of mixture in the evap basin is left this is done as too much evaporation would leave behind a powder. we want salt crystals leave to cool, soon after, crystals will form