acids, alkalis and titrations

Question 1

acids are substances that turn litmus paper what colour

Answer 1

red, yellow or orange

Question 2

acids have a pH

Answer 2

below 7

Question 3

bases turn litmus paper what colour

Answer 3

sark green, blue or purple

Question 4

what are bases called if they dissolve in water

Answer 4

alkali’s

Question 5

bases react with _____ in acids

Answer 5

H+ ions

Question 6

use of universal indicator

Answer 6

measure pH of a solution

Question 7

colour of universal indicator with acid

Answer 7

red

Question 8

colour of universal indicator with alkali

Answer 8

blue

Question 9

use of phenolphalein indicator

Answer 9

determine the end point of a strong alkali or weak acid

TITRATIONS

Question 10

what is an alkali

Answer 10

a soluble base

Question 11

colour of phenolphthalein indicator in acid

Answer 11

colourless

Question 12

colour of phenolphthalein indicator in alkali

Answer 12

pink

Question 13

colour of methyl orange in acid

Answer 13

red

Question 14

colour of methyl orange in alkali

Answer 14

yellow

Question 15

how is universal indicator used

Answer 15

a drop of it is added to the solution and colour is matched to the colour chart which indicates the pH

Question 16

use of methyl orange indicator

Answer 16

determine the end point of a strong acid- strong alkali or strong acid- weak alkali

TITRATIONS

Question 17

When acids are added to water they form

Answer 17

positive hydrogen ions

Question 18

what makes a solution acidic

Answer 18

presence of hydrogen ions

Question 19

when alkalis are added to water, what is formed

Answer 19

negative hydroxide ions

Question 20

what makes a solution alkaline

Answer 20

hydroxide ions

Question 21

what happens when an acid and an alkali react

Answer 21

a neutralisation reaction

Question 22

Ionic equation of neutralisation ( H)

Answer 22

H⁺ + OH⁻ —-> H₂O

Question 23

4 common indicators

Answer 23

litmus
universal
phenolphthalein
methyl orange

Question 24

the point at which an indicator changes colour is known as the

Answer 24

end point

Question 25

neutralisation is

Answer 25

a reaction between a base/alkali and an acid which forms a salt and water

Question 26

what is a base

Answer 26

a proton acceptor ( they are metal oxides, hydroxides or carbonates)

Question 27

strong acids in do what water

Answer 27

completely ionize

Question 28

properties of strong acids (3)

Answer 28

produce high concentrations of H+ ions in solution - have a low pH 0-3 - react more vigorously with metals, carbonates and bases

Question 29

weak acids do what in water

Answer 29

partially ionize

Question 30

if weak acids only partially ionize in water, what does that mean about the H+ions

Answer 30

only some of their molecules release H+ions

Question 31

properties of weak acids (3)

Answer 31

- produce lower concentration of H+ions in solution - have a pH of 4-6 - react less vigorously compared to strong acids

Question 32

carboxylic acids are what type of acids

Answer 32

weak acids

Question 33

carboxylic acids contain a functional group of what atoms (3) and how are they arranged

Answer 33

carbon , hydrogen and oxygen atoms COOH

Question 34

Examples of carboxylic acids

Answer 34

methanoic ( HCOOH) ethanoic ( HC₃ COOH)

Question 35

How do bases neutralise acids

Answer 35

by combining with the hydrogen ions in them

Question 36

word reaction of a base neutralising an acid

Answer 36

acid + base ---> salt + water

Question 37

acids in aqueous solution are a source of what ions

Answer 37

positive hydrogen ions

Question 38

alkalis in aqueous solution are a source of what ions

Answer 38

negative hydroxide ions

Question 39

titrations are a method of

Answer 39

analysing the concentration of solutions

Question 40

acid-base titrations determine

Answer 40

exactly how much alkali is needed to neutralise a quantity of acid – and vice versa

Question 41

Titrations can also be used to prepare

Answer 41

salts

Question 42

PRACTICAL- HOW TO CARRY OUT AN ACID- BASE TITRATION

Answer 42

- Place exactly 25cm³ sodium hydroxide in conical flask - Place the conical flask on a white tile so the tip of the burette is inside the flask - Add a few drops of a suitable indicator to the solution in the conical flask Perform a rough titration by taking the burette reading and running in the solution in 1 – 3 cm3 portions, while swirling the flask vigorously Quickly close the tap when the end-point is reached (sharp colour change) and record the volume, placing your eye level with the meniscus Now repeat the titration with a fresh batch of sodium hydroxide As the rough end-point volume is approached, add the solution from the burette one drop at a time until the indicator just changes colour Record the volume to the nearest 0.05 cm3 Repeat until you achieve two concordant results (two results that are within 0.1 cm3 of each other) to increase accuracy