bonding and structure (topic 2)

Question 1

Answer 1

Question 2

Answer 2

carbon

Question 3

(2)

Answer 3

• the atoms are different sizes
• so there are no layers to slide

Question 4

what percentage of the atoms in the alloys are atoms of X

Answer 4

2/27 x 100
7.4%

Question 5

what type of substance is an alloy

Answer 5

mixture

Question 6

Answer 6

Question 7

(5)

Answer 7

• electrons transferred from potassium to sulfur
• two potassium atoms each lose one electron
• forming K+ ions
• sulfur atoms gain 2 electrons
• forming S^2− ions

Question 8

Answer 8

there are no gaps / sticks between the potassium ions and sulfide ions

Question 9

Answer 9

Question 10

Answer 10

the forces between iodine molecules are stronger

Question 11

Answer 11

brown

Question 12

Answer 12

it contains ions which can move

Question 13

Answer 13

hydrogen iodine

Question 14

(4)

Answer 14

• giant structure / lattice
• made up of atoms / positive ions
• with delocalized / free electrons
• so electrons can move / flow through the metal

Question 15

describe how the structure of an alloy is different from the structure of a pure metal (2)

Answer 15

• an alloy is a metal which has different types of atoms
• alloy has distorted layers

Question 16

why is nitinol used in dental braces

Answer 16

can return to its original shape

Question 17

suggest one reason why coins are not made of pure copper, do not give cost as a reason

Answer 17

(pure copper is too) soft

Question 18

aluminium is manufactured by the electrolysis of a molten mixture of cryolite and

Answer 18

aluminium oxide

Question 19

how can the same reaction produce two different products

Answer 19

• different conditions
• different catalyst
• different pressure
• different temperature

Question 20

Answer 20

• place a lighted splint at the mouth of the tube
• there is a squeaky pop

Question 21

why is hydrogen, and not magnesium, produced at the cathode

Answer 21

• hydrogen is less reactive than magnesium
• (whichever element is lower down the reactivity series or is less reactive will go to the cathode)

Question 22

give one reason why metal spoons are sometimes silver plated

Answer 22

• to improve appearance
• to prevent corrosion

Question 23

(4)

Answer 23

• solution must be silver nitrate or contain silver ions
• otherwise copper will be deposited or silver will not be deposited
• spoon must be the cathode
• because silver ions have a positive charge

Question 24

why is it difficult to electroplate plastic spoons

Answer 24

because plastic is an insulator or does not conduct electricity

Question 25

the three metals in stainless steel have different sized atoms, stainless steel is harder than pure iron, explain why (2)

Answer 25

• structure is distorted
• so it is difficult for layers to slide

Question 26

the bonds between the atoms in graphene are

Answer 26

covalent

Question 27

explain why graphite is used in pencils (2)

Answer 27

• layers can slide
• because there are no bonds between layers
• (so pieces of graphite rub off and are left on paper)

Question 28

explain why metals can be shaped (2)

Answer 28

• made of layers
• which can slide

Question 29

name the acid used to make magnesium sulfate

Answer 29

sulfuric acid

Question 30

use the equation to help you to describe what you would observe when magnesium reacts with the acid (2)

Answer 30

• hydrogen gas produced
• magnesium disappears into solution
• gets hot

Question 31

how could you obtain solid magnesium sulfate from this solution

Answer 31

• crystallisation
• evaporation