Topic 3 - Chemical Changes

Question 1

Acids in solution are a source of

Answer 1

Hydrogen ions(H+ ions). The higher the concentration of H+ ions, the lower the pH.

Question 2

Alkalis in solution are a source of

Answer 2

Hydroxide ions(OH- ions). The higher the conc of OH- ions, the higher the pH.

Question 3

Neutral, acidic and alkali solution pH

Answer 3

Neutral - 7
Acidic - <7
Alkali - >7

Question 4

A base is

Answer 4

A substance that reacts with an acid to make a salt and water

Question 5

Alkalis are

Answer 5

Bases that are soluble in water

Question 6

Acids and alkali effect on litmus paper

Answer 6

In an acid, blue litmus turns red
In an alkali, red litmus turns blue

Question 7

Acids and alkali effect on methyl orange

Answer 7

Turns red in an acid and yellow in an alkali

Question 8

Acid and alkali effect on phenolphthalein

Answer 8

Colourless in acid, pink in alkalis

Question 9

The higher the concnetration of H+ ions in an acid,

Answer 9

The stronger the acid and lower the pH

Question 10

The higher the concentration of OH- ions in an alkali,

Answer 10

The stronger the alkali and higher the pH

Question 11

An increase by a factor of 10 to H+ concentration leads to

Answer 11

A decrease in pH by 1

Question 12

The steps of the neutralisation practical between calcium oxide and dilute hydrochloric acid

Answer 12

Measure out a certain amount of hydrochloric acid using a pipette.
Measure a fixed mass of calcium oxide
Mix them
Wait for the calcium oxide to all react, then measure the pH and add more.
Repeat until there is an excess

Question 13

Dilute means

Answer 13

There is a low concentration of a substance in the solution

Question 14

Concentrated means

Answer 14

There is a high concentration of a substance in a solution

Question 15

What makes an acid strong

Answer 15

They ionise almost completely in water. A large proprotion of the acid molecules dissociate to release H+ ions. Low pH

Question 16

What makes an acid weak

Answer 16

The dont fully ionise in solution. A small amount of molecules dissociate into H+ ions. Higher pH.

Question 17

The difference between strong and concentrated acids

Answer 17

Concentration shows how much acid is in the water but strength shows how many acid molecules ionise in water.

Question 18

A reaction between an acid and a base is called

Answer 18

A neutralisation reaction

Question 19

A salt is

Answer 19

An ionic compond

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

Steps of hydrogen test

Answer 24

Put a lighted splint into the test tube.
If hydrogen is present there will be a squeaky pop

Question 25

Steps of Carbon dioxide test using limewater

Answer 25

Bubble the CO2 gas through limewater. If it turns cloudy, CO2 is present

Question 26

In an acid-alkali neutralisation reaction what reacts

Answer 26

H+ ions and OH- ions react to make water

Question 27

You can make a soluble salt by

Answer 27

Reacting an acid with an insoluble base Reacting an acid with a soluble base(alkali)

Question 28

Steps of making a soluble salt with an acid and insoluble base

Answer 28

Add excess reactant to remove all acid Filter off excess to get a solution of the salt and water

Question 29

Steps of making a soluble salt with an acid and alkali

Answer 29

A titration must be used because you cant tell if there is an excess They need to be mixed in the correct proportions because it is soluble so will contaminate it in excess Once they neutralise using an indicator, there iso nly the salt and water remaining

Question 30

Steps of turning a solution of copper sulfate to crystals

Answer 30

Add to evaporating dish and evaporate some of the water with a water bath. Then leave to evaporate until pure dry crystals of copper sulfate are produced

Question 31

Steps of titration practical for an acid-alkali neutralisation to make crystals

Answer 31

Measure out a set amount of alkali into a flask using a pipette Add a bit of indicator to flask Fill a burette with an acid of known concentration Add a little at a time to the flask, until the indicator shows it has been neutralised Then use the method of making crystals in an evaporating dish

Question 32

All common salts of sodium, potassium and ammonium are

Answer 32

Soluble

Question 33

Nitrates are

Answer 33

Soluble

Question 34

Common chlorides are... except

Answer 34

Soluble(except silver and lead chloride)

Question 35

Common sulfates are...except

Answer 35

Soluble(except lead, barium and calcium sulfate)

Question 36

Common carbonates and hydroxides are...except

Answer 36

Insoluble(except sodium, potassium and ammonium)

Question 37

A precipitate forms if

Answer 37

An insoluble salt and water is formed.

Question 38

An insoluble salt is formed

Answer 38

By two certain soluble salts react

Question 39

Steps of preparing a pure dry sample of an insoluble salt

Answer 39

Mix two soluble salts in solution together. A precipitate should form in water. Filter through filter paper so the water goes int othe beaker and insoluble salt gets stuck. Leave the salt to dry on a piece of filter paper in the oven

Question 40

Electrolytes are

Answer 40

Ionic compounds either molten or aqueous

Question 41

Electrolysis is

Answer 41

The breaking down of a substance using electricity

Question 42

Cathode

Answer 42

negatively charged electrode

Question 43

Anode

Answer 43

positively charged electrode

Question 44

During electrolysis ions move to where

Answer 44

Positve ions move to the cathode Negative move to the anode

Question 45

When a molten substance is electrolysed, the products are

Answer 45

The same as the substance originally

Question 46

When an aqueous solution is electrolysed, the products are

Answer 46

Can be metal ions or hydrogen ions at the cathode, so the product is either a metal or hydrogen gas Can be halide ions or OH- at the anode, so either halide molecules or oxygen is formed

Question 47

In aqueous solutions, the product at the cathode depends on

Answer 47

If the metal is more reactive than hydrogen. If it is more reactive, hydrogen is formed. if its not, then a solid layer of the pure metal will form.

Question 48

In aqueous solutions, th product at the anode depends on

Answer 48

If halide ions are present, a haldie molecule is formed. If there is no halide ions, then oxygen is formed

Question 49

Copper chloride solution products

Answer 49

Cathode - copper Anode - Chlorine

Question 50

Sodium sulfate solution products

Answer 50

Cathode - hydrogen Anode - Oxygen

Question 51

Water acidified with sulfuric acid electrolysis products

Answer 51

Cathod - Hydrogen Anode - Oxygen

Question 52

During electrolysis the processes are

Answer 52

Reduction - A gain in electrons Oxygen - A loss of electrons

Question 53

Reduction occurs at the

Answer 53

Cathode

Question 54

Oxidation occurs at the

Answer 54

Anode

Question 55

Hlaf equations show

Answer 55

The elctrons lost or gained by ions resulting in the product during electrolysis

Question 56

Copper sulfate solution products elctrolysis when inert electrodes are used

Answer 56

Cathode - Copper Anode - Oxygen

Question 57

Core practical of copper sulfate solution electrolysis uses electrodes made of

Answer 57

Copper

Question 58

When copper electrodes are used in a solution of copper sulfate, th result is

Answer 58

Copper getting transferred form the anode to the cathode. This makes the mass of the cathode increase and the mass of the anode decrease.

Question 59

Electrolysis of copper sulfate solution using copper elctrodes steps

Answer 59

Set up like normal, and leave for 30 misn for copper to move through the solution Measure original mass and final mass of elctrodes