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

common acids

Answer 6

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

Question 7

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 1) i increas 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 ans so the pH increases

Question 18

during neutralisation reactions explain how is a salt produced

Answer 18

salts are produced by replacing the hydrogen ions with metal ions

Question 19

method to prepare a solute

Answer 19

1) add excess of base
2) gently warm the mixture to speed up reaction
3) filter to remove the untracked solid from the solution
4) heat to evaporate water and concentrate the salt solution
5) leave to evaporate water slowly for crystallisation to occur

Question 20

what’s the difference between base and an alkali

Answer 20

base is insoluble, alkali is soluble

Question 21

what happens in a titration

Answer 21

• acid is added from à 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

Question 22

end-point

Answer 22

when the indicator changes colour

Question 23

how to make a pure dry salt

Answer 23

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

Question 24

general equation for reaction of metal and an acid

Answer 24

metal + acid -> salt + H2 (MASH2)

Question 25

general equation for reaction of metal carbonate and an acid

Answer 25

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

Question 26

precipitation reaction

Answer 26

in a precipitation reaction is one in which a soluble substance in a solutions* i cause an insoluble precipitate to form

Question 27

precipitate

Answer 27

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

Question 28

what is the test for carbon dioxide

Answer 28

limewater