Topic 4 - Acid and Alkali

Question 1

acidic pH

Answer 1

less than 7

Question 2

alkali pH

Answer 2

more than 7

Question 3

neutral pH

Answer 3

7

Question 4

how can you find the pH of a solution

Answer 4

using indicators

Question 5

indicator

Answer 5

a substance that changes colour depending on the pH

Question 6

name common acids

Answer 6

• hydrochloric acid (HCl)
• sulfric acid (H2SO4)
• nitric acid (HNO3)

Question 7

name a common alkali

Answer 7

• sodium hydroxide (NaOH)

Question 8

what ion does acids contain

Answer 8

H+

Question 9

what ion does alkalis contain

Answer 9

OH-

Question 10

what ion does neutral solutions contain

Answer 10

even concentration of H+ and OH- ions

Question 11

concentrated solution

Answer 11

contains a lot of dissolved solute per unit volume

Question 12

dilute solution

Answer 12

contains only a small amount of solute

Question 13

difference in concentration of H+ ions in acid pH

Answer 13

each time (each number) you go down in pH the concentration of H+ ions i increases by 10x

Question 14

concentration equation

Answer 14

amount dissolved / volume of solution

Question 15

bases

Answer 15

substances that neutralise acids to form a salt and water only

Question 16

base + acid reaction

Answer 16

base + acid -> salt + H20 (BASH20)

Question 17

during neutralisation reactions explain why the pH becomes neutral

Answer 17

the hydrogen ions combine with oxide ions to form water; this removes the hydrogen ions and so the pH increases

Question 18

what’s the difference between base and an alkali

Answer 18

base is insoluble, alkali is soluble

Question 19

what happens in a titration

Answer 19

• a pipette measures a fixed volume of alkali and then it goes in a conical flask
• acid is added from a burette to a fixed volume of alkali in a conical flask
• a few drops of indicator are added to the alkali so you can follow the reaction
• eventually the solution will reach end-point -> inductor will change colour
• phenolphthalein: colourless = acidic, pink = alkali

Question 20

end-point

Answer 20

when the indicator changes colour

Question 21

how to make a pure dry soluble salt using an acid and a soluble reactant

Answer 21

• carry out a titration
• note the exact volume of acid needed to neutralise the alkali using an indicator
• use the burette to add the correct volume of acid without the indicator
• evaporate the water from the solution formed and leave to crystallise
• filter off solid and dry it

Question 22

general equation for reaction of metal and an acid

Answer 22

metal + acid -> salt + H2 (MASH2)

Question 23

general equation for reaction of metal carbonate and an acid

Answer 23

metal carbonate + acid -> salt + H20 + CO2 (CASH2OCO2)

Question 24

what is precipitation reaction

Answer 24

in a precipitation reaction two soluble solutions are mixed which causes an insoluble precipitate to form (need to pick right solutions)

Question 25

precipitate

Answer 25

cause (a substance) to be deposited in solid form from a solution

Question 26

what is the test for carbon dioxide

Answer 26

limewater

Question 27

Difference between single indicator and universal indicator

Answer 27

Single indicator only tells if substance is acidic or alkali (one colour change) however universal indicator provides a more detailed indication of how acidic or alkali substances by displaying a variety of colours of the pH scale

Question 28

spectator ion

Answer 28

An ion from the acid that does not change during a reaction

Question 29

Oxidation

Answer 29

Loss of electrons in a reaction

Question 30

reduction

Answer 30

gain of electrons in a reaction

Question 31

how do you work out the ionic equation?

Answer 31

Crossover method

Question 32

what happens when two solutions containing soluble cells react together?

Answer 32

The endings swap e.g. Copper sulphate + potassium carbonate -> copper carbonate + potassium sulphate

Question 33

solubility of common chlorides

Answer 33

all soluble (except silver & lead chlorides)

Question 34

solubility of common sulphates

Answer 34

all soluble (except lead, barium & calcium sulphate)

Question 35

solubility of common nitrates

Answer 35

all soluble

Question 36

name a piece of equipment that could be used to measure the pH of a substance more accurately than universal indicator paper

Answer 36

pH meter

Question 37

precipitation reaction method (insoluble salt from two soluble solutes)

Answer 37

- add 1 spatula of the soluble solute to a test tube and add deionised water to dissolve it -> shake throughly - do the same with the other soluble solute - tip the solutions into a small beaker and stir well -> the insoluble salt should precipitate out - filter the contents of the beaker - swill out beaker with more deionised water to make sure all the soluble solutions been washed away and filter again - rinse contents of filter paper with deionised water to make sure all the soluble solutions been washed away - scrape out the insoluble precipitate and leave to dry in an oven to evaporate any remaining water to ensure a pure, dry sample

Question 38

solubility of common carbonates and hydroxides

Answer 38

all insoluble (except sodium, potassium & ammonium)