principles of chemistry Flashcards
isotopes
-isotopes are different atomic forms of the same element, which have the same number of protons but different numbers of neutrons
how to separate rock salt
-grind up the rock salt with a pestle and mortar
-dissolve it in a breaker and stir
-filter through filter paper in a funnel
-evaporate in an evaporating dish
what is chromatography used for
-method used by chemists to separate out mixtures
how to carry out paper chromatography
-draw a line near the bottom of a sheet of filter paper)pencil as they are insoluble
-add spots of different inks to the line at regular intervals
-loosely roll the sheet up and put it in a beaker of solvent(water)
-make sure the level of solvent is below the baseline(so ink doesn’t dissolve into the solvent
-place a lid on top of the container to stop solvent evaporating
-the solvent will seep up the paper, carrying the inks with it
-each different dye in the inks will move up the paper at a different rate and form a spot in a different place
-when the solvent has nearly reached the top of the paper take the paper out of the beaker and leave it to dry
-end results is a pattern of spots called a chromatogram
how to calculate the Rf value for each chemical
Rf = distance travelled by solute/distance travelled by solvent
distillation
-solution is heated
-the part of the solution that has the lowest boiling point evaporates
-the vapour is then cooled, condenses(turns back into a liquid and is collected)
-rest of the solution is left behind in the flask
neutralisation
-add excess solid to the acid
-stir the mixture to make sure reaction is complete
-filter the mixtures to remove excess
-transfer the solution into an evaporating dish
-heat up the filtrate until saturated
-check saturation point using a glass rod
-if crystals form then saturation point has been reached
-allow to cool and crystalise
-filter to remove crystals
-dry crystals in a warm oven
titration
-using a pipette, add alkali(usually 25 cm3) to a conical flask, along with two or three drops of indicator
-fill a burette with the acid
-using burette add the acid to the alkali a bit at a time, giving the conical flask a regular swirl
-the indicator changes colour when all the alkali has been neutralised
-record the volume of acid used to neutralise the alkali
precipitation
-mix the solutions
-stir the mixture
-filter off the precipitate
-wash with distilled water
-dry the solid in warm oven
metal + acid
salt +hydrogen
carbonate + acid
salt + carbon dioxide + water
alkali + acid
salt +water
base + acid
salt + water
are common salts of sodium potassium and ammonium soluble
-soluble
nitrates solube?
yes
common chlorides soluble
yes except silver and lead
common sulfates soluble
yes except lead, barium and calcium
common carbonates soluble
no except sodium potassium and ammonium
common hydroxides soluble
no except sodium potassium and calcium
test for chlorine
-chlorine bleaches damp blue litmus paper, turning it white
-might turn red first as chlorine solution is acidic
test for oxygen
oxygen relights a glowing splint
test for carbon dioxide
CO2 turns limewater cloudy-bubble the gas through a test tube of limewater
test for hydrogen
-hydrogen makes a squeaky pop with a lighted splint
test for ammonia
-ammonia turns damp red litmus paper blue
reactivity series
potassium
sodium
lithium
calcium
magnesium
aluminium
zinc
iron
copper
silver
gold
how to prevent rusting
Barrier methods
-painting/coating with plastic to keep -out the water and oxygen
Sacrificial methods
-zinc is often used as a sacrificial metal
-zinc is more reactive than iron, further up in the reactivity series
-zinc will be oxidised instead of iron
-a coating of zinc can be sprayed onto the object-known as galvanising
-big blocks of zinc can be bolted to the iron, used on ships’ hulls or on underground iron pipes
equation for rust
iron + oxygen + water ->hydrated iron III oxide (rust)
how can you measure how catalysts affect rate
-decomposition of hydrogen peroxide
-add hydrogen peroxide to a beaker attached to a gas syringe with a bung
-add manganese oxide powder to the hydrogen peroxide
-measure the volume of gas produced at regular time intervals and record the results
-repeat the experiment using copper oxide(same amount of catalyst)
-plot a graph
catalyst
Catalyst: A substance that speeds up a chemical reaction while remaining chemically unchanged at the end of
the reaction.
A catalyst is not used up in a reaction.
A catalyst speeds up a reaction by providing an alternative pathway with lower activation energy.
