SC4 - ACIDS AND ALKALIS

Question 1

acids contain ___ ions

Answer 1

hydrogen ions H+

Question 2

alkalis contain ___ ions

Answer 2

hydroxide ions OH-

Question 3

hydrochloric acid formula

Answer 3

HCl

Question 4

sulphuric acid formula

Answer 4

H2SO4

Question 5

nitric acid formula

Answer 5

HNO3

Question 6

ways of measuring pH (2)

Answer 6

• using an indicator and comparing the colour with the pH scale (less accurate)
• using a digital pH meter (more accurate, to the decimal point)

Question 7

pH of acids

Answer 7

pH 1-7

Question 8

pH of a neutral substance eg. water

Answer 8

pH 8

Question 9

pH of alkalis

Answer 9

9-14

Question 10

UNIVERSAL INDICATOR: colour in acid

Answer 10

red / orange / yellow

Question 11

UNIVERSAL INDICATOR: colour in neutral

Answer 11

green

Question 12

UNIVERSAL INDICATOR: colour in alkali

Answer 12

purple / blue

Question 13

PHENOLPHTHALEIN: colour in acid

Answer 13

colourless

Question 14

PHENOLPHTHALEIN: colour in alkali

Answer 14

pink

Question 15

METHYL ORANGE: colour in acid

Answer 15

red

Question 16

METHYL ORANGE: colour in alkali

Answer 16

yellow

Question 17

give the names of 3 indicators

Answer 17

• universal indicator
• phenolphthalein
• methyl orange

Question 18

concentrated acid definition

Answer 18

containing a large amount of acid than water in the solution

Question 19

dilute acid definition

Answer 19

containing a small amount of acid than water in the solution

Question 20

strong acid definition

Answer 20

• all of the acid splits up into H+ ions (dissociates) when dissolved in water
• high concentration of H+
  -low pH

Question 21

weak acid definition

Answer 21

• only some of the acid splits up into H+ ions when dissolved in water
• lower concentration of H+
• higher pH (still acidic)

Question 22

the concentration of hydrogen ions decreases by a factor of __ every time the pH is increased by _

Answer 22

decreases by a factor of 10 every time the pH is increased by 1

Question 23

base definition

Answer 23

• a metal oxide or hydroxide eg. CuO or Ca(OH)2
• bases can neutralisé acids to give salt and water only

Question 24

general equation for base + acid

Answer 24

BASHO
base + acid -> salt + water

Question 25

salts formed by hydrochloric acid (HCl)

Answer 25

chlorides

Question 26

salts formed by sulphuric acid (HSO4)

Answer 26

sulphates

Question 27

salts formed by nitric acid (HNO3)

Answer 27

nitrates

Question 28

describe how to make a salt by reacting a base with an acid eg. copper sulphate from copper oxide + sulphuric acid

Answer 28

- add EXCESS BASE to acid to neutralise all the acid - FILTER off the excess base - EVAPORATE the water from the solution to get crystals of the salt - dry the crystals in an oven

Question 29

alkali definition

Answer 29

a base that is soluble in water

Question 30

describe how to do a titration experiment

Answer 30

- using a PIPETTE transfer a known volume of alkali into a CONICAL FLASK - add a few drops of INDICATOR (methyl orange or phenolphthalein) - add acid from a BURETTE slowly until you are near the indicator changing colour - add the acid drop-wise until the indicator changes colour - record the volume of acid used

Question 31

general equation for metal + acid

Answer 31

MASH metal + acid -> salt + hydrogen

Question 32

test for hydrogen gas

Answer 32

when a lit splint is added to the test tube, it makes a squeaky pop

Question 33

general equation for metal carbonate + acid

Answer 33

CASHOCO metal carbonate + acid -> salt + water + carbon dioxide

Question 34

test for carbon dioxide gas

Answer 34

lime water turns milky when carbon dioxide is bubbled through it

Question 35

describe precipitation reactions

Answer 35

- salts that are insoluble can be made using precipitation reactions - the metal and non-metal part of two compounds swap round to give two new compounds - if one of these is insoluble it forms a precipitate

Question 36

SOLUBLE SALTS

Answer 36

- sodium carbonate, potassium carbonate, ammonium carbonate - all nitrates - all chlorides except lead chloride, silver chloride - all sulphates except calcium sulphate, lead sulphate, barium sulphate - all ammonium salts - all group 1 metal salts

Question 37

INSOLUBLE SALTS

Answer 37

- all carbonates except sodium carbonate, potassium carbonate, ammonium carbonate - lead chloride, silver chloride - calcium sulphate, lead sulphate, barium sulphate