Atmosphere and acids - TN Flashcards
at what pH would a substance be considered a strong/weak acid/alkali
0-3 strong acid
4-6 weak acid
8-10 weak alkali
11-14 strong alkali
how does methyl orange change colour with pH
red yellow yellow
what colours is universal indicator in varying pHs
four most abundant gases and their percentages
nitrogen - 78
oxygen - 21
argon - 0.96
carbon dioxide - 0.04
how do we measure the percentage of oxygen experimentally
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
what is element combustion
when an element reacts with oxygen to produce an oxide
what is he word equation of element combustion
element + oxygen -> element oxide
what substance forms after the element combustion of a metal and what state of matter is it in
metal oxide
solid
what substance forms after the element combustion of a non-metal and what state of matter is it in
non-metal dioxide
gas
describe the combustion of magnesium in oxygen
creates magnesium oxide
observations:
- bright white light
- white powder formed
describe the combustion of sulfur in oxygen
creates sulfur dioxide
observe a blue flame
describe the combustion of hydrogen in oxygen
creates hydrogen oxide (water)
observe a squeaky pop
two charges of iron
2+ and 3+
charge of zinc
Zn2+
charge of silver
Ag+
charge of copper
Cu2+
charge of lead
Pb2+
why is the chemical test for oxygen when a glowing splint relights
because the oxygen allows the wood in the splint to combust more efficiently
how would you test to see if an unknown element was a metal or a non-metal
- combust in oxygen (to create the element oxide)
- dissolve the oxide formed
- check the pH of the solution with an indicator
what pH solutions do metal oxides form
alkaline
what pH solutions do non-metal dioxides form
acidic
define an acid
H+ donor
difference between alkali and base
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)
Define a base
H+ acceptor
define an alkali in terms of the transfer of ions
OH- donor
why are acids acidic
because H+ ions cause a low pH, and these are what acids donate when dissolved
why are alkali alkaline
because OH- ions cause a high pH, and these are what alkali donate when dissolved
why do bases cause a high pH when dissolved
name the five most important acids
hydrochloric acid
nitric
sulfuric
phosphoric
carbonic
name the three most important and the main trend of alkalis
- sodium hydroxide
- potassium hydroxide
- ammonium hydroxide
all soluble metal hydroxides
name the most important and the main trend of bases
ammonia
- all metal oxides
- all metal hydroxides
what is a polyatomic ion
an ion that contains more than one atom
eg NO3 - and SO4 2-
word equation for the reaction between acids an bases
acid + base -> salt + water
observations seen in an acid+base reaction
- the base disappears (because it has been used up in the reaction
what reaction can be used to make salt crystals
acid + base
what are the four steps for making soluble salt crystals using the insoluble base method
word equation for the reaction between acids and carbonates
acid + carbonate -> salt + water + carbon dioxide
observations of the reaction between acids and carbonates
- carbonate disappears (it is used up in the reaction)
- effervescence (CO2 gas produced)
during an acid/base reaction or an acid/carbonate reaction, what would the result be if the salt produced was soluble
it would dissolve into the water to form a salt solution
eg:
