atmosphere and acids 3.4 Flashcards
what’s the composition of the air?
nitrogen - 78 %
oxygen - 21 %
argon - 0.96 %
carbon dioxide - 0.04 %
how can we measure the percentage of oxygen?
by reacting it with another element, and the air gradually decreases until all of the oxygen has been added to the element
to work out the percentage:
decrease in volume / initial volume of air x 100 = %
why do some experiments fail?
leak in apparatus
wasn’t heated long enough for all the oxygen to be reacted
what affect mass?
heating on yellow flame as the door adds to mass
not heating for long enough
something has escaped
what is the equation for element combustion?
element + oxygen > element oxide
what affects the name and state of the oxide?
whether it is a metal or non-metal
metal - oxide, solid
non-metal - dioxide, gas
what’s important about the element combustion of magnesium?
produces a bright white light and white power
what’s important about the element combustion of sulphur?
blue flame
what’s important about the element combustion of hydrogen ?
squeaky pop
what’s the charge of iron (||)?
Fe 2+
what’s the charge of iron (|||)?
Fe 3+
what’s the charge of copper?
Cu 2+
what’s the charge of silver?
Ag +
what’s the charge of zinc?
Zn 2+
what’s the charge of lead?
Pb 2+
what’s the chemical test for oxygen?
glowing splint > relights
as the oxygen allows the wood in splint to combust more efficiently
what type of solution does a metal oxide form?
alkaline solution
what type of solution does a non-metal dioxide form?
acidic solution
what’s the acid name, acid formula and ion formula for nitrate?
nitric acid
HNO3
NO3 -
what’s the acid name, acid formula and ion formula for sulphate?
sulphuric acid
H2SO4
SO4 2-
what’s the acid name, acid formula and ion formula for phosphate?
phosphoric acid
H3PO4
PO4 3-
what’s the acid name, acid formula and ion formula for carbonate?
carbonic acid
H2CO3
CO3 2-
what’s the alkali name, alkali formula and ion formula for ammonium?
ammonium hydroxide
NH4OH
NH4 +
what’s the ion formula for hydroxide?
OH -
what’s the chemical test for carbon dioxide?
limewater > turns cloudy
CO2 reacts with the limewater to insoluble white solid
a pH greater than 7 is …
alkaline
a pH of 7 is …
neutral
a pH less than 7 is …
acidic
in an acidic solution methyl orange indicator would turn:
red
in an neutral solution methyl orange indicator would turn:
yellow
in an alkaline solution methyl orange indicator would turn:
yellow
in an acidic solution phenolphthalein indicator would turn:
colourless
in an neutral solution phenolphthalein indicator would turn:
colourless
in an alkaline solution phenolphthalein indicator would turn:
pink
in an acidic solution red litmus paper would turn:
stay red
in an neutral solution red litmus paper would turn:
stay red
in an alkaline solution red litmus paper would turn:
blue
in an acidic solution blue litmus paper would turn:
red
in an neutral solution blue litmus paper would turn:
stay blue
in an alkaline solution blue litmus paper would turn:
stay blue
universal indictor range of colours depending on pH:
0,1,2 : red
3,4 : orange
5,6 : yellow
7 : green
8,9,10 : light blue
11,12,13: dark blue
14 : purple
how do you determine whether an unknown element is a metal or non-metal?
- combust in it oxygen
- dissolve the oxide formed
- check the pH of the solution with an indicator
metal oxide - alkaline solution
non- metal dioxide - acidic solution
what is the acid and base reaction?
acid + base > salt + water
for example
sulphuric acid + zinc oxide > zinc sulphate + water
what is an important observation in an acid + base reaction?
base disappears
this is because it is used up in reaction
what do you need to remember about the salt formed from a base and acid reaction?
if salt is soluble, it dissolves to form a salt solution
we can use an acid + base reaction to make …
salt crystals
how do you make zinc sulphate crystals?
- add excess base (ZnO) to hot acid (H2SO4)
this makes sure that the salt solution is made quickly and ensures all the acid is used up - filter out the excess base (ZnO)
salt solution (ZnSO4) is the filtrate and is collected in an evaporating basin - heat salt solution (ZnSO4) until crystals start to from around the edges
this saturates the solution so that crystals form most efficiently - leave salt solution to crystallise
evaporation of water allows crystals to form
what is the acid and carbonate reaction?
acid + carbonate > salt + water + carbon dioxide
for example
lead carbonate + sulphuric acid > lead sulphate + water + carbon dioxide
what are the two important observations in an acid + carbonate reaction?
carbonate disappears
- as it is used up in reaction
fizzing
- as gas of carbon dioxide is produced
what do you need to remember about the salt formed from a carbonate and acid reaction?
if salt is soluble, it dissolves to form a salt solution
