Atmosphere and acids - TN

Question 1

at what pH would a substance be considered a strong/weak acid/alkali

Answer 1

0-3 strong acid
4-6 weak acid
8-10 weak alkali
11-14 strong alkali

Question 2

how does methyl orange change colour with pH

Answer 2

red yellow yellow

Question 3

what colours is universal indicator in varying pHs

Answer 3

Question 4

four most abundant gases and their percentages

Answer 4

nitrogen - 78
oxygen - 21
argon - 0.96
carbon dioxide - 0.04

Question 5

how do we measure the percentage of oxygen experimentally

Answer 5

react with another element, often a metal.
- the air gradually decreases in volume until all of the oxygen has been reacted
- using a measuring cylinder, measure the change in volume
- %O = (decrease in volume)/(initial volume) x 100

if in the experiment the volume does not decrease by 21%,:
–the metal wasn’t heated for long enough for all the oxygen to be reacted
–there was a leak in the apparatus

Question 6

what is element combustion

Answer 6

when an element reacts with oxygen to produce an oxide

Question 7

what is he word equation of element combustion

Answer 7

element + oxygen -> element oxide

Question 8

what substance forms after the element combustion of a metal and what state of matter is it in

Answer 8

metal oxide
solid

Question 9

what substance forms after the element combustion of a non-metal and what state of matter is it in

Answer 9

non-metal dioxide
gas

Question 10

describe the combustion of magnesium in oxygen

Answer 10

creates magnesium oxide

observations:
- bright white light
- white powder formed

Question 11

describe the combustion of sulfur in oxygen

Answer 11

creates sulfur dioxide

observe a blue flame

Question 12

describe the combustion of hydrogen in oxygen

Answer 12

creates hydrogen oxide (water)

observe a squeaky pop

Question 13

two charges of iron

Answer 13

2+ and 3+

Question 14

charge of zinc

Answer 14

Zn2+

Question 15

charge of silver

Answer 15

Ag+

Question 16

charge of copper

Answer 16

Cu2+

Question 17

charge of lead

Answer 17

Pb2+

Question 18

why is the chemical test for oxygen when a glowing splint relights

Answer 18

because the oxygen allows the wood in the splint to combust more efficiently

Question 19

how would you test to see if an unknown element was a metal or a non-metal

Answer 19

1. combust in oxygen (to create the element oxide)
2. dissolve the oxide formed
3. check the pH of the solution with an indicator

Question 20

what pH solutions do metal oxides form

Answer 20

alkaline

Question 21

what pH solutions do non-metal dioxides form

Answer 21

acidic

Question 22

define an acid

Answer 22

H+ donor

Question 23

difference between alkali and base

Answer 23

it is always a base. if it is soluble it can also be called an alkali

an alkali is a soluble base (it can dissolve in water)

Question 24

Define a base

Answer 24

H+ acceptor

Question 25

define an alkali in terms of the transfer of ions

Answer 25

OH- donor

Question 26

why are acids acidic

Answer 26

because H+ ions cause a low pH, and these are what acids donate when dissolved

Question 27

why are alkali alkaline

Answer 27

because OH- ions cause a high pH, and these are what alkali donate when dissolved

Question 28

why do bases cause a high pH when dissolved

Answer 28

Question 29

name the five most important acids

Answer 29

hydrochloric acid nitric sulfuric phosphoric carbonic

Question 30

name the three most important and the main trend of alkalis

Answer 30

- sodium hydroxide - potassium hydroxide - ammonium hydroxide all soluble metal hydroxides

Question 31

name the most important and the main trend of bases

Answer 31

ammonia - all metal oxides - all metal hydroxides

Question 32

what is a polyatomic ion

Answer 32

an ion that contains more than one atom eg NO3 - and SO4 2-

Question 33

word equation for the reaction between acids an bases

Answer 33

acid + base -> salt + water

Question 34

observations seen in an acid+base reaction

Answer 34

- the base disappears (because it has been used up in the reaction

Question 35

what reaction can be used to make salt crystals

Answer 35

acid + base

Question 36

what are the four steps for making soluble salt crystals using the insoluble base method

Answer 36

Question 37

word equation for the reaction between acids and carbonates

Answer 37

acid + carbonate -> salt + water + carbon dioxide

Question 38

observations of the reaction between acids and carbonates

Answer 38

- carbonate disappears (it is used up in the reaction) - effervescence (CO2 gas produced)

Question 39

during an acid/base reaction or an acid/carbonate reaction, what would the result be if the salt produced was soluble

Answer 39

it would dissolve into the water to form a salt solution eg: