chemistry unit 3,4

Question 1

reactant definition

Answer 1

starting material in the chemical reaction

Question 2

percentage yield formula

Answer 2

percentage yield = actual amount / theoretical amount x 100

Question 3

amount of nitrogen in the air %

Answer 3

78.1

Question 4

amount of oxygen in the air %

Answer 4

21

Question 5

amount of argon in the air

Answer 5

0.9

Question 6

amount of carbon dioxide in the air

Answer 6

0.04

Question 7

noble gas features

Answer 7

they have full outer shell
colorless, odorless

Question 8

sources of co2

Answer 8

respiration, decomposition, volcanic activity

Question 9

consequences of global warming

Answer 9

• polar ice caps could melt
• sea levels could rise
• there could be more extreme weather ( floods, droughts, heat waves)

Question 10

corrosion definition

Answer 10

gradual destruction of metals by chemical reactions with substances in the environment
over time, corrosion changes the appearance and properties of a material as it breaks down and become weaker

Question 11

metal that rusts

Answer 11

iron

Question 12

what’s redox reaction

Answer 12

oxidation is loss of electrons
reduction os gain of electrons

Question 13

alkaline metals properties

Answer 13

very soft
shiny
low melting and boiling point
low density
stored in oil to prevent it from reacting

Question 14

what does alkaline metals form when it reacts with water

Answer 14

alkaline compounds

Question 15

lithium flame test colour

Answer 15

red

Question 16

sodium flame test colour

Answer 16

yellow

Question 17

potassium flame test colour

Answer 17

lilac

Question 18

how does flame test work for alkali metals

Answer 18

when a alkali metal is heated, the electrons in its atom gain energy and more to vacant outer shells. as the electrons lose energy and move back to lower shells, they smit visible lights
the movement of electrons are different for each element, so it gives off a unique flame colour

Question 19

halogens properties

Answer 19

• 7 electrons in outer shells
• can easily obtain outer shell by gaining 1 electron
• can gain an electron in reaction to form negative ions
• can form single covalent bond with another atom
  -exists as diatomic molecules

Question 20

acid rain PH range

Answer 20

lower than 5.5

Question 21

empirical formula

Answer 21

percentage / atomic mass

Question 22

reactivity order

Answer 22

potassium
sodium
lithium
calcium
magnesium
aluminium
carbon
zinc
iron
lead
hydrogen
copper
silver
gold
platinum

Question 23

concentration formula

Answer 23

concentration = mol / vol

Question 24

solubility rules

Answer 24

• nitrates ade all soluble
• chlorides are all soluble except silver / lead
• all group 1 are soluble
• all carbonates are insoluble except group 1
• all hydroxides are insoluble unless other rule exists
• all sulfates are soluble except lead, barium, calcium, silver

Question 25

metal + acid ->

Answer 25

salt + hydrogen

Question 26

metal oxide + acid ->

Answer 26

salt + water

Question 27

metal hydroxide + acid ->

Answer 27

salt + water

Question 28

metal carbonate + acid ->

Answer 28

salt + carbon dioxide + water