C5 Chemical Changes

Question 1

What is an ore?

Answer 1

A rock which contains enough metal to make it economically worthwhile to extract

Question 2

What is the reactivity series?

Answer 2

A list of metals in order of their reactivity, with the most reactive at the top and the least reactive ones at the bottom

Question 3

How are metals put in order of reactivity?

Answer 3

Looking at their reactions with:
Water
Dilute acid

Question 4

What gas is given off when metals react with water or dilute acid? What is the test for it?

Answer 4

Hydrogen
It pops with a lighted splint

Question 5

what is formed when metals react with oxygen?

Answer 5

metal oxides

Question 6

what is gaining oxygen called?

Answer 6

oxidation

Question 7

what is losing oxygen called?

Answer 7

reduction

Question 8

what does reacting a metal with water produce?

Answer 8

metal hydroxide and hydrogen

Question 9

what affects how reactive a metal is?

Answer 9

it depends on the metal’s ability to lose electrons and form a positive ion

Question 10

how are unreactive metals found?

Answer 10

by themselves as they are so unreactive

Question 11

what does displacement mean?

Answer 11

a more reactive element will push out (displace) a less reactive element from its compound

Question 12

why is carbon used in extracting metals?

Answer 12

it is very cheap

Question 13

what is OILRIG?

Answer 13

oxidation is loss (of electrons)
reduction is gain (of electrons)

Question 14

what does (aq) mean?

Answer 14

aqueous solution - dissolved in water

Question 15

what do acids produce in aqueous solutions?

Answer 15

hydrogen ions (H+)

Question 16

what is a base?

Answer 16

a chemical which can neutralise and acid producing a salt and water

Question 17

what are bases usually?

Answer 17

metal oxides or metal hydroxides

Question 18

what is an alkali?

Answer 18

a base which is soluble in water

Question 19

what ions do alkalis form in aqueous solutions?

Answer 19

hydroxide ions (OH-)

Question 20

what is the range of pHs for acids?

Answer 20

0 - <7

Question 21

what is neutral on the pH scale?

Answer 21

7

Question 22

what is the range of pH values for alkalis?

Answer 22

> 7 - 14

Question 23

what happens to the H+ and OH- ions in a neutralisation reaction?

Answer 23

they react to produce water

Question 24

what do all acids contain?

Answer 24

hydrogen

Question 25

what can metals before hydrogen on the reactivity series do?

Answer 25

displace hydrogen

Question 26

what is the general equation for an acid reacting with a metal?

Answer 26

metal + acid –> salt + hydrogen

Question 27

what salts does hydrochloric acid produce?

Answer 27

ones ending in -chloride

Question 28

what salts does sulfuric acid produce?

Answer 28

ones ending in -sulfate

Question 29

how does magnesium react with acids?

Answer 29

rapidly as it is high up on the reactivity series
magnesium also easily forms ions so the reaction is rapid

Question 30

how does zinc react with acids?

Answer 30

quite rapidly as it is more reactive than hydrogen
zinc also forms ions quite easily so reacts quite rapidly

Question 31

how does iron react with acids?

Answer 31

fairly slowly as it is only more reactive than hydrogen by a small amount
iron does not easily form ions so the reaction is slow

Question 32

which molecules are reduced and which are oxidised when a metal reacts with an acid?

Answer 32

hydrogen ions are reduced (they gain electrons) and become hydrogen gas
metal atoms are oxidised (lose electrons) to become metal ions

Question 33

what is produced when a base or alkali reacts with and acid?

Answer 33

salt and water

Question 34

what does nitric acid produce?

Answer 34

salts ending with -nitrate

Question 35

what ions do salts contain?

Answer 35

a positive ion from the base or alkali
a negative ion from the acid

Question 36

what are the products of a metal carbonate reacting with an acid?

Answer 36

salt
water
carbon dioxide

Question 37

what does ionised mean?

Answer 37

when a molecule splits into ions in water
e.g. when an acid molecule splits into hydrogen ions and negative ions

Question 38

what is a strong acid?

Answer 38

an acid where the acid molecules fully ionise in aqueous solutions

Question 39

what is a weak acid?

Answer 39

an acid where the molecules partially ionise in aqueous solutions.
the reaction is reverseable

Question 40

what does the pH scale say about hydrogen ions?

Answer 40

it gives an idea of the concentration of hydrogen ions

Question 41

how do pHs differ with strong and weak acids?

Answer 41

strong acids have a lower pH than weak acids for a given concentration.
this is because a strong acid has more hydrogen ions as they fully ionise

Question 42

what happens when the pH scale decreases by 1 unit?

Answer 42

the concentration of hydrogen ions increases by 10 times

Question 43

what does the concentration of an acid tell you?

Answer 43

the amount of acid molecules in a given volume of solution