C5 Chemical Changes Flashcards
What is an oxidation reaction?
An reaction where something gains oxygen
What does “it has been oxidised mean”?
When it has gained oxygen
What does it mean if something has been reduced?
It has lost oxygen
What the PH scale?
Whta is a neutral (number
What is a low or high called
It measires how acidic somethig is
Goes from 0-14
The lower it is the more acidic it is
The higher it is the more alkaline it is
A neutral substance is a 7
What is the universla indicator?
Something (based on colors) that when added to a solution will react to form a colour which can be checked to see what acidity it is
How else could you calucate the acidity of something?
Using a PH probe
What is an acid?
A substance that formes an aq solution with a ph less that 7
What is an alkali??
A base that disloves in water tp form a solition with a PH value of more than 7 and which forms OH- ions in water
Give the reaction between acids and base:
Acid+Base = Salt+Water
Or it could be said like this
H+(aq) + OH-(aq) = H*2O(l)
What do acids produce in water?
Protons
Hydrogen ions (which is the same as a proton)
What dp acids do in a aq solution?
They ionise
Of an alkali as solution reacts with a acid then what is alwayes formed
OH-ions
What is the equation for neutralisation?
H+(aq)+ OH-(aq)=H2O(l)
Acid+Alkali
Acid+Alkali=Salt + Water
Acid+Metal carbonate
Acid+Metal carbonate = Salt+ Water+Carbon Dioxide
What is a PH probe?
Attacked to a PH meter it can also measure the PH of a substance electronicly and really acuratly. It will give you a number.
What do acids produce in water?
They ionise in an aq solution and produce H+ ions
What happens when a strong acid meets water?
It ionise completely. All the acid particles dissociate to release H+ ions
Give 3 examples of a strong acid?
Sulfuric, hydrochloric and nitric acids
What happens when a week acid meets water?
It doesn’t fully ionise. Only a small portion of the acid particles dissociate to release H+ ions
Give 3 examples of a week acid?
Ethanoic, citric and carbonic acids
When a week acid is ionised can it be reverced?
When a strong acid is ionised can it be reverced?
Yes as only a few of the acid particles ionised
No as all of the acids ionised
Why are strong acids more reactive than week acids?
The reaction is with H+ ions and other substances. So if the concentration of H+ ions is bigger (eg in strong acids) then there will be a quicker and more reactive
What exactly is the PH of a substance measuring?
The amout of H+ ions in a solition
If PH decrease by 1 what happenes to the amount of H+ ions?
They have increased by a factor of 10
If PH decrease by 2 what happenes to the amount of H+ ions?
They have increased by a factor of 100
If they have the same concentration what do we know about the PH’s of week and strong acids?
The PH of a strong acid is always less than a weeker acid
What does the strength of an acid tell you?
What proportion of the acid molecules ionised into the water
What does the concentration of an acid tell you?
How much acid there is in a certian volume of water
How watered down the acid is
When will the concentration of the acid be at the highest?
When there is a high amount of acid in a small amount of water
When will the concentration of the acid we at it’s weekest?
When there is little acid molecules in a large volume of water
When will PH decrease? (concentration)
PH will decrease when the acid concentration increases westher it is a strong or weak acid
What is a base?
Something that ends in oxide or hydroxide
What is a alkli
A base that is disolved in water
Give the equasion between an acid and a carbonate?
Acid + (Metal) Carbonate = Salt + Water + Carbon dioxide
Is it possible to make an soluable salt using an insoluable base?
Yes
What is a reactivity series?
A table listing metals in order of their reactivity with other substances
How are metals placed in the reactivity series
It depends on how easily they loose an electron
The higher they are in the series the more easy it is for them to lose an electron
Where will the metal be which reacts the most easily with water or acids?
At the top as that involves loosing an electron
How could you make your own reactive series?
By reacting metals with an acid or water. And putting the metals in order top to bottom of the most-least reactive
What is the equasion when a metal reacts with an acid?
Acid + Metal = Salt + Hydrogen (gas)
How could you estimate the speed of the reaction between Acids and Metal?
What will change is the Metal is more reactive?
The speed of the reaction is indicated by the rate of which the bubbles (of hydrogen) are given off
The bubbles will be given off faster
The temprature change
Give the equasion between a acid and a metal?
Acid + Metal = Salt + Hydrogen
Give the equasion between Metal and Water?
Metal + Water = Metal Hydroxide + Hydrogen
How are oxides formed?
What is this an example of?
Common metals such as iron or aluminium react with oxygen
This is an example of oxidation
What is oxidation (not in terms of electrons)?
When something gains oxygen
What is oxidation (in terms of electrons)?
When something looses electorns
OILRIG
What is a reduction reaction?
A reaction that seperates metals from oxygen so that you can use the metal
What is a reaction that seperates metals from oxygen called?
A reduction reaction
What is reduction (not in terms of electrons)?
The loss of oxygen
Give the reduction reaction of copper?
2CuO + C = 2Cu + CO^2
Give the reaction where magnesium oxidises?
2Mg + O^2 = 2MgO
How may some ores be reduced?
By using Carbon as it will bond with the Oxygen
Give an example of reduction with Carbon?
Fe^2O^3 + 3C = 4Fe + 3CO^2
Iron(III) oxide + Carbon = Iron + Carbon dioxide
What are the 2 ways to extract a metal from it’s ore?
Electrolysis
Reduction with Carbon
What determines if electrolysos will be used of reduction with carbon?
If the metal is higher than carbon in the reactivity series then elecrolysis will need to be used as Carbon won’t displace the metal
Where else. If carbon is below the metal in the reactivity series then it can be reduced by carbon
Why is Gold found in it’s element form?
It is so unreactive that it is found by itself
Magnesium, Zinc And iron reactions
.
How does magnesisum react in a dilute acid?
It reacts vigerously with cold dilute acids and produces a lot of bubbles
How does zink react with a dilute acid?
It reacts slowly with dilute acids but more strongly if you heat them up
How does iron react with a dilute acid?
It reacts slowly with dilute acids but more strongly if you heat them up
