chemical changes Flashcards
what is a titration
used to find unknown concentration of an acid or alkali
equipment needed for titration
pipette
conical flask
burette
white tile
titration practical
-use a …… to add ….. cm^3 of ……. to a clean ……. …… .
-add few drops of …. and put …… ….. on a ….. …..
-fill …… with ……. ….. and note starting volume
-slowly add the …. from the ….. to the …. in the …… ….., swirling to mix
-stop adding the ….. when the ….. changes color (when neutralised)
-note final reading, and calculate total volume of …. added.
-repeat until you get results that are 0.1 cm^3 of each other, then calculate mean
-pipette, 25, alkali, conical flask
-indicator, conical flask, white tile
-burette, sulfuric acid
-acid, burette, alkali, conical flask
-acid, indicator
-acid
name an indicator to use in titrations
-methyl orange
-litmus
-phenolphthalein
what is meniscus
the curve of a liquid when it touches a material
convert cm to dm
/ by 1000
how to calculate no. of moles
concentration x volume
how to calc concentration
no. of moles/volume
what is a redox reaction
a reaction where reduction and oxidation happen at the same time
why use a pipette and why use a burette
pipette measures a fixed volume
(accurately)
(but) burette measures variable
volume
what is an electrolyte
liquid or solution containing an ionic compound (ions are free to move)
the right electrode is
the left electrode is
the left electrode is cathode -
the right electrode is anode +
what does it mean when an ion gets discharged at an electrode
the atom goes from a charged ion to a neutral atom
electrolysis is a process where
you can separate ionic compounds into their pure elements by passing an electric current through an electrolyte
how to turn an aluminum oxide ore into molten aluminum oxide
- purify the ore
- mix with mineral cryolite (this lowers melting point)
- melt
ionic equation for water
H^+ + OH^-
which ion in an aqueous solution of electrolysis will get discharged on a cathode
the least reactive element
which ion in an aqueous solution of electrolysis will get discharged on an anode
- if a halide is present (group 7) then that will be the one to get discharged
- else the hydroxide ion gets discharged
Why do electrodes need to be constantly replaced
because o2 is formed which reacts with the C of the electrode forming co2 and gradually burns away
an acid is a substance that forms
aqueous solutions of pH less than 7
because they ionise, to release H+ ions
what is a strong acid
-an acid that ionises completely
-the reactants turn completely into products
what is a weak acid
don’t fully ionise to release hydrogen ions
-ionisation of a weak acid is reversible
what do metal hydroxides and oxide form when reacting w/ an acid
salt + water
what do metal carbonates form when reacting with an acid
salt + water + carbon dioxide
what do metal carbonates form when reacting with an acid
salt + water + carbon dioxide
how to form a soluble salt using an acid and insoluble base
- put dilute acid in a beaker and gently heat w/ bunsen burner
- add to the insoluble base until it doesn’t dissolve
- the base is an excess and acid is now neutralized
- filter out the excess base
- heat solution to the evaporate some water
- when crystal start forming leave it to cool
- filter and dry the crystals
To work out the formula of the salt,
take +ve ion from base, such as sodium from sodium oxide (Na2O), and -ve ion from acid, such as chloride from hydrochloric acid (HCl), and combine together
