C4 chemical changes Flashcards
what happens when a metal and an oxygen react
they form a metal oxide
reactivity of metals is related to what
there tendency to create positive ions
what is the rule of displacement in metals
A more reactive metal can displace a less reactive metals from a compound
where are the most reactive metals on the reactivity scale
the top
what metals can be extracted from their compound by reduction
metals that are less reactive than carbon
give the equation of an oxidised sodium (Na)
Na -> Na+ + e-
if sodium +1 ion is reduced give the equation
Na+ + e- -> Na
what is produced when an acid reacts with a metal
salt + hydrogen
what is a redox reaction
a reaction between acid and metal where one substance is reduced and one is oxidised
what is produced in a neutralisation reaction
salt and water
what is made when acid reacts with metal carbonate
salt and water and carbon dioxide
what does soluble mean
can dissolve
what is titration
an experiment used to determine the amount of an acid or alkali to become neutral
describe how to do a titration experiment
- Fill burette with 100cm acid with the meniscus’ base on the 100cm3 line
- Use 25cm3 pipette to add 25cm3 of alkali into a conical flask, drawing alkali into the pipette using a pipette filler
- Add a few drops of a suitable indicator to the conical flask (eg: phenolphthalein which is pink when alkaline and colourless when acidic)
- Add acid from burette to alkali until end-point is reached (as shown by indicator)
- The titre (volume of acid needed to exactly neutralise the acid) is the difference between the first (100cm3) and second readings on the burette
- Repeat the experiment to gain more precise results
how do you work out the concentration of an acid
- Convert volumes into dm3
- Work out the moles of acid
moles = volume x concentration - Work out mole ratio from equation
- Work out concentration
how many cm3 are there in 1 dm3
1dm3= 1000cm3
what happens to strong acids in aqueous solution
they are completely ionised forming H+ ions
what happens to weak acids in aqueous solutions
partially ionised forming H+ ions
what happens as the PH decreases by 1
hydrogen concentration increases by 10
what is electrolysis
passing current through a molten substance so the solution can be broken down into elements
what is an electrolyte
the substance being broken down by electrolysis
what metals are extracted using electrolysis (molten)
those that are more reactive than carbon
what do aqueous solutions create at the cathode (negative electrode)
hydrogen unless the metal is
less reactive than hydrogen this is because more reactive ions want to stay within the solution
what is produced at the anode (positive electrode)
At the positive electrode, if OH- and halide ions (Cl-, Br-, I-) are present, then one of the halide ions will be produced. If no halide is present, oxygen is formed.
