Topic 3 Chemical Changes(complete)

Question 1

Solutions with ph lower than 7 are

Answer 1

Acids

Question 2

Solutions with ph higher than 7 are

Answer 2

Alkaline

Question 3

Neutral solution has ph of

Answer 3

7

Question 4

Acids form what ions in water

Answer 4

H+

Question 5

Alkalis form what ions in water

Answer 5

OH-

Question 6

Stronger acids have higher/lower ph
Weaker acids have higher/lower ph

Answer 6

Stronger acids lower
Weaker acids higher

Question 7

Stronger alkalis have higher/lower ph
Weaker alkalis have higher/lower ph

Answer 7

Stronger alkalis higher
Weaker alkalis lower

Question 8

What colour is litmus in acidic ,alkaline and neutral solutions

Answer 8

Acidic red
Neutral purple
Alkaline blue

Question 9

What colour is methyl orange in acidic ,alkaline and neutral solutions

Answer 9

Acidic red
Neutral yellow
Alkaline yellow

Question 10

What colour is phenolphthalein in acidic ,alkaline and neutral solutions

Answer 10

Acidic colourless
Neutral colourless
Alkaline pink

Question 11

If the concentration of H+ ions increase what happens to the ph

Answer 11

Ph will decrease

Question 12

If the concentration of OH- ions increase what happens to the ph

Answer 12

Ph will increase

Question 13

As the concentration of h+ ions increases or decreases by factor of 10 how much will ph change

Answer 13

Ph will increase or decrease by 1

Question 14

If an acid is concentrated what does it mean

Answer 14

Means there is more acid per volume of water
Dilute acid meaning there is less acid per volume of water

Question 15

What does it mean for an acid to be strong or weak

Answer 15

Strong acids dissociate completely in water to release H+ ions
Weak acids don’t dissociate completely in water

Question 16

What is a base

Answer 16

Substance that reacts with an acid to produce salt and water

Question 17

Alkalis are soluble bases

Question 18

HCl + NaOH —> NaCl + H20
Acid + base —> Salt + Water

Answer 18

H+ + OH- —> H20

Question 19

What is a salt

Answer 19

An ionic compound
Metal and non metal
Eg NaCl

Question 20

Acid + Metal Oxide—->?

Answer 20

Salt +Water

Question 21

Acid +Metal Hydroxide—->?

Answer 21

Salt +Water

Question 22

Acid + Metal—->?

Answer 22

Salt +Hydrogen

Question 23

Acid + Metal Carbonate —-> ?

Answer 23

Salt + Water + Carbon dioxide

Question 24

What is the test for hydrogen

Answer 24

Use lighted splint and place near what your testing for hydrogen and if you hear squeaky pop hydrogen is present

Question 25

What is the test for carbon dioxide

Answer 25

Bubble gas testing for carbon dioxide through limewater and is present if limewater turns cloudy

Question 26

What is the reaction between an acid and a base known as

Answer 26

Neutralisation reaction

Question 27

How is water made in neutralisation reactions

Answer 27

H+ ions from acid react with OH- ions from alkali

Question 28

When making soluble salts why do you first need to add excess reactant to the solution

Answer 28

To make sure all the acid has reacted and none leftover

Question 29

What do you do after adding excess reactant(base) to an acid and base and all acid has been neutralised

Answer 29

Use filtration to remove excess solid to be left with only salt and water from neutralisation reaction

Question 30

What must you add to solution during titration to know when acid and alkali have been neutralised

Answer 30

Use an indicator

Question 31

Measure out set amount of acid and add few drops of 1_____ into 2_____ flask with acid Add alkali from the 3_____ into acid until colour change signalling the solution has been 4_____ Repeat until you get 5______ results

Answer 31

1 indicator 2 conical 3 burette 4 neutralised 5 concordant

Question 32

After you get concordant result from titration and repeat reaction using that result what do you do

Answer 32

Slowly evaporate water off Filter out the solid and left with pure dry salt

Question 33

What is added under conical flash during titration to see colour change easier

Answer 33

White tile

Question 34

What should you do with flask to ensure the acid is distributed evenly in alkali in titration

Answer 34

Swirl the flask regularly

Question 35

Common salts of sodium potassium and ammonium (solubility?)

Answer 35

Soluble

Question 36

Nitrates(solubility?)

Answer 36

Soluble

Question 37

Chlorides (solubility?)

Answer 37

Soluble Except silver and lead chloride

Question 38

Sulfates (solubility?)

Answer 38

Soluble Except lead, barium and calcium sulfate

Question 39

Carbonates and hydroxides (solubility?)

Answer 39

Insoluble Except sodium,potassium and ammonium ones

Question 40

What is a precipitation reaction

Answer 40

Reaction between 2 right soluble salts to make an insoluble one

Question 41

What insoluble salt could be made from this precipitation reaction Lead nitrate + sodium chloride —->

Answer 41

Lead nitrate + sodium chloride —-> lead chloride + sodium nitrate Lead chloride is the insoluble salt

Question 42

Describe the method use to make pure dry sample of insoluble salt lead chloride

Answer 42

Add lead nitrate to one test tube of water and shake thoroughly and same with sodium chloride Mix the 2 substances and the lead chloride should precipitate out With the new mixture do filtration and should be left with lead chloride in filter paper as it not soluble Rinse the filter paper with water and leave to dry or scrape off

Question 43

What is an electrolyte

Answer 43

Ionic compounds in molten state or dissolved in water

Question 44

Define electrolysis

Answer 44

Process in which electricity decomposes an electrolyte

Question 45

Describe movement to both ions to each electrode

Answer 45

Cations move to the cathode Anions move to the anode

Question 46

What will the electrolyte potassium chloride form at each electrode and why

Answer 46

Cathode :potassium (potassium ions have positive charge and are attracted to the negatively charged cathode ) Anode: chlorine (chlorine ions have negative charge and are attracted to positively charged anode )

Question 47

What reactions happen at the the anode and the cathode

Answer 47

Anode - negative ions are oxidised(lose electrons Cathode -positive ions are reduced(gain electrons)

Question 48

Explain oxidation

Answer 48

Gain of oxygen Loss of electrons

Question 49

Explain reduction

Answer 49

Loss of oxygen Gain of electrons

Question 50

Write Hal equation for electrolysis of aluminium oxide at cathode and anode

Answer 50

Anode O2- -2e—-> O (Oxygen made) Cathode Al3+ + 3e ——> Al (Aluminium made)

Question 51

Explain what happens during electrolysis to obtain pure copper using electrolyte copper sulfate

Answer 51

Cathode is made of pure copper and anode made of impure copper At anode the impure copper turns into its cation and moves to the pure copper cathode All over cations move to the pure copper cathode and become reduced(gain electrons)