C5 - chemical changes Flashcards
how is the position of the metals in the reactivity series decided?
By how easily they lose electrons
Metal + acid -> …
salt + hydrogen
Metal + water -> …
metal hydroxide + oxygen
metal + oxygen -> …
metal oxide
elements above carbon in the reactivity series are Extracted using what method?
electrolysis
Elements below carbon in the reactivity series are extracted using what method
Displacement using carbon or thermal decomposition
What does it mean if an ore is high-grade
it contains a high percentage of the metal
what equipment is used during electrolysis?
-beaker
-electrodes (anode and cathode)
-battery
what do you call the positive and neagative electrode?
positive - anode
negative - cathode
how does electrolysis for lead bromide work?
-the negative bromide ions will be attracted to the positive anode and when they get there they’ll be discharged, which just means that they go from a charged ion to a neutral atom, then they’ll usually float off as a gas.
-Meanwhile the positive lead ions will be attracted to the negative cathode and again be discharged this time to form pure lead which will then fall to the bottom and from a layer of molten lead
what is phytoming?
phytomining is when plants are grown on land which contains a metal compound that we want. The plants take in the metal compounds, which are stored in their tissues. The plants then harvested and burned; the ash contains a high concentration of the metal compound.
name 3 common acids and their chemical formulas?
H 2 SO 4 - sulfuric acid
HCl - hydrochloric acid
CH 3 COOH - ethanoic acid
what is bioleaching?
by leaching is when bacteria is mixed with the metal or, chemical reactions take place which leads to the production of a solution called leachate. The leachate contains a metal compound that we want to extract
as temperatue increases, solubility (in water) …
increases
what makes a soltion an acid or an alkali?
if it has H+ ions then acid and if it has OH- then alkali
on a pH curve what do you call the point where the indicator changes colour?
the end point
what do you call it when ther is equal conc. of acid and alkali?
the equivilent point
what makes an acid a strong acid or a weak acid?
its a strong acid if all molecules ionise (dissociate to form ions) or a weak acid if not 100% of the molecules ionise.
explain why it is possible to have a very dilute solution of a strong acid, with a higher pH value than a concentrated solution of a weak acid.
- pH depends on concentration of H + ions
-so although weak acid does not ionise completely, it could have a
higher concentration of H + ions if amount of strong acid per
decimetres cubed is very ,very small
-strong acids ionise completely
-but in very dilutes solution may produce fewer H plus ions in a given
volume of solution than a concentrated solution of a weak acid
give 4 reasons why propanoic acid is descrobed as a weak acid and nitric acid is descriobed as a strogn on.
- Propanoic acid does not ionise completely when added to water
- only a small fraction form H + ions
-therefore, propanoic acid does not produce a high concentration of H plus ions as a strong acid and equal concentration - nitric acid is a strong acid, because it’s molecules ionise completely in water+
