3.4 - Atmosphere & acids Flashcards
(100 cards)
1
Q
what four gases is air composed of
A
nitrogen
oxygen
argon
carbon dioxide
2
Q
how much nitrogen is in air
A
78%
3
Q
how much oxygen is in air
A
21%
4
Q
how much argon is in air
A
0.96%
5
Q
how much carbon dioxide is in air
A
0.04%
6
Q
how do you measure the percentage of oxygen in air
A
by reacting it with another element - often a metal
the air gradually decreases in volume until all of the oxygen has been added to the metal
7
Q
what element might you heat to measure the percentage of oxygen
A
copper to form copper oxide
8
Q
how do you calculate the percentage of O2 in air
A
decrease in volume / initial volume of air x 100 = (should be 21)
9
Q
why might the air in one of the percentage oxygen experiment not decrease by 21%
A
- the metal wasn’t heated for long enough for all the oxygen to be reacted
- there’s a leak in the apparatus
10
Q
what is element combustion
A
when an element reacts with oxygen to produce an oxide
11
Q
what is the word equation for element combustion
A
element + oxygen –> element oxide
12
Q
what is the oxide name of a metal
A
metal oxide
13
Q
what state is a metal oxide
A
solid
14
Q
what is the oxide name of a non-metal
A
non-metal dioxide
15
Q
what state is a non-metal dioxide
A
gas
16
Q
what does magnesium combust to form
A
magnesium oxide
17
Q
what is the word equation for the combustion of magnesium
A
magnesium + oxygen –> magnesium oxide
18
Q
what is the chemical equation for the combustion of magnesium
A
2Mg(s) + O2(g) –> 2MgO(s)
19
Q
what are the observations of the combustion of magnesium
A
bright white light
white powder formed
20
Q
what does sulphur combust to form
A
sulphur dioxide
21
Q
what is the word equation for the combustion of sulphur
A
sulphur + oxygen –> sulphur dioxide
22
Q
what is the chemical equation for the combustion of sulphur
A
S(s) + O2(g) –> SO2(g)
23
Q
what is an observation of the combustion of sulphur
A
blue flame
24
Q
what does hydrogen combust to form
A
water
25
what is the word equation for the combustion of hydrogen
hydrogen + oxygen --> water
26
what is the chemical equation for the combustion of hydrogen
2H2(g) + O2(g) --> 2H2O(l)
27
what is an observation of the combustion of hydrogen
squeaky pop
28
what is the ion formula of Iron(II)
Fe 2+
29
what is the ion formula of Iron(III)
Fe 3+
30
what is the ion formula of Copper
Cu 2+
31
what is the ion formula of Silver
Ag+
32
what is the ion formula of Zinc
Zn 2+
33
what is the ion formula of Lead
Pb 2+
34
what is the chemical test for oxygen
glowing splint - relights
because the oxygen allows the wood in the splint to combust more efficiently
35
what solutions do metal oxides form when dissolved in water
alkaline
36
what solutions do non-metal dioxides form when dissolved in water
acidic
37
how can you determine whether an unknown element is a metal or non-metal
1- combust it in oxygen
2- dissolve the oxide formed
3- check the pH of the solution with an indicator
38
what is an acid
H+ donor
39
what is a base
H+ acceptor
40
what is an alkali
OH- donor
41
what does an acid, alkali or base describe
a solution in terms of ions
42
what does acidic or alkaline describe
a solution in terms of pH
43
what happens with acids in water
acids dissolve and then donates H+ ions into the water
this causes the solution to have a pH < 7 and for it to be acidic
44
what happens with alkalis in water
alkalis dissolve and the donate OH- ions into the water
this causes the solution to have a pH > 7 and for it to be alkaline
45
what happens to bases in water
bases dissolve and then accept H+ ions from the H2O molecules
but when a H2O molecule loses a H+ ion what's leftover is an OH- ion
it's the OH- ions that cause the solution to have a pH > 7 and for it to be alkaline
46
what are important acids
hydrochloric acid
nitric acid
sulphuric acid
phosphoric acid
carbonic acid
47
what is the formula of hydrochloric acid
HCl
48
what is the formula of nitric acid
HNO3
49
what is the formula of sulphuric acid
H2SO4
50
what is the formula of phosphoric acid
H3PO4
51
what is the formula of carbonic acid
H2CO3
52
what are important alkalis
sodium hydroxide
potassium hydroxide
ammonium hydroxide
(all soluble metal ions)
53
what is the formula of sodium hydroxide
NaOH
54
what is the formula of potassium hydroxide
KOH
55
what is the formula of ammonium hydroxide
NH4OH
56
what are some important bases
ammonia
(all metal oxides)
(all metal hydroxides)
57
what is the formula of ammonia
NH4
58
what is a polyatomic ion
an ion that contains more than one atom
59
what is the ion name of nitric acid
nitrate
60
what is the ion formula of nitrate
NO3 -
61
what is the ion name of sulphuric acid
sulphate
62
what is the ion formula of sulphate
SO4 2-
63
what is the ion name of phosphoric acid
phosphate
64
what is the ion formula of phosphate
PO4 3-
65
what is the ion name of carbonic acid
carbonate
66
what is the ion formula of carbonate
CO3 2-
67
what is the ion name of all alkalis
hydroxide
68
what is the ion formula of all alkalis
OH -
69
what is the ion name of ammonium hydroxide (alkali)
ammonium
70
what is the ion formula for ammonium (alkali)
NH4 +
71
what is it impotant to use when writing polyatomic ions in chemical formulae
brackets
72
what would magnesium nitrate formula look like
Mg (NO3)2
73
what do bases react with metals to form
salt and water
74
what is the equation for acid and base reaction
acid + base --> salt + water
75
what is the important observation in and acid + base reaction
the base disappears because it is used up in the reaction
if the salt is soluble, it dissolves into the water to form a salt solution
76
what reaction is used to make salt crystals
acid + base reaction
77
explain how to make salt crystals
1- add excess base into a hot acid (this makes the salt solution quickly and ensures all the acid is used up)
2- filter out excess base ( the salt solution is the filtrate and is collected in the evaporating basin)
3- heat the salt solution until crystals start to form around the edges (this saturates the solution so that crystals form more efficiently)
4- leave the salt solution to crystalise (evaporation of water allows crystals to form)
78
soluble salt equation
acid(aq) + base(s)/ alkali(aq) --> salt (aq) + water(l)
79
how do you make pure dry crystals of soluble salt
1- make the salt solution
a) insoluble base method
b) titration method
2- crystalise the salt
80
when do you use the insoluble bases method
when making salts that do not contain Na+, K+ or NH4 + ions
81
what is the acid usually in the insoluble base method
one of hydrochloric acid (HCl), sulfuric acid(H2SO4) or nitric acid (HNO3)
82
what is a base usually in the insoluble base method
a solid metal oxide
83
explain the insoluble base method
1- heat the acid (hot acid has more energy so it reacts faster with the base)
2- while stirring, add base until no more will dissolve (this guarantees the base is in excess so that we know all the acid has been used up)
3- filter out the excess base
84
when do you use the titration method
Na+, K+ or NH4+ ions because their bases are all soluble so you wouldn't be able to filter out the excess if you used the insoluble base method
85
what is the acid usually in the titration method
one of hydrochloric acid (HCl), sulfuric acid (H2SO4) or nitric acid (HNO3)
86
what is the alkali usually in the titration method
one of sodium hydroxide (NaOH), potassium hydroxide (KOH) or ammonium hydroxide (NH4OH)
87
explain the titration method
1- perform a titration to measure the volumes of acid and alkali that neutralise each other
2- repeat the titration but
a) don't put the indicator in
b) use the burette to add exactly the right volume for neutralisation
88
what is crystalisation
once you've made a salt solution, you perform crystalisation to get pure, dry salt crystals
(done in the same way, regardless of which method you used to make the salt solution)
89
explain crystalisation
1- heat the salt solution until crystals just start forming
(you can tell by looking at the edges, or by occasionally dipping in a glass rod - this causes the solution to become saturated)
2- allow the solution to cool in an evaporating basin for a few days - this lowers the solubility of the salt so that lots of salt crystals form
3- filter out the crystals - this removes them from excess salt solutions in the basin
4- dry the crystals by dabbing them with filter paper - this removes the last traces of the water from the crystals
90
what do carbonates react with metals to form
a salt,water and carbon dioxide
91
what is the acid and carbonate equation
acid + carbonate --> salt + water + carbon dioxide
92
what are the two observations in an acid + carbonate reaction
the carbonate disappears - because it is used up in a reaction
there is fizzing - because a gas(carbon dioxide) is produced
93
what is the chemical test for carbon dioxide
limewater turns cloudy
94
what is a precipitate
an insoluble solid that forms inside a solution
95
how does a precipitate form
the ions in the solution collide with each other, a precipitate forms and slowly sinks to the bottom
96
how can you tell if a precipitate will form
by mixing the ions up and seeing if either of the resulting compounds is insoluble
if an insoluble compound is formed it will appear as a precipitate
97
how do you make insoluble salts
by mixing solutions to make a precipitate
each solution should contain one of the ions needed to make it
98
what are the ions called that aren't involved in making the precipitate
spectator ions and they remain in the solution as leftovers
99
what is an ionic equation
a simpler equation for the reaction just involving the precipitate
100
explain how you separate the salt from the solution after it has been made by precipitation
1- filter out the salt precipitate - the residue is the salt we want to keep + the filtrate is the leftover solution
2- rinse the salt was water - this washed off traces of the leftover solution, it doesn't dissolve the salt because it is insoluble
3- dry the salt by dabbing it with filter paper - this removes the last few traces of water, leaving us with a pure dry salt
