Chemical reactions Flashcards
What does metal + oxygen make
A metal oxide
Oxidation in terms of oxygen?
Element/ compound that has been oxidised = gained oxygen
Reduction in terms of oxygen?
Element/ compound that has been reduced = lost oxygen?
How to test a metal’s reactivity?
React with water at room temperature:
Potassium + sodium + lithium = react very rapid
Calcium = fairly rapid reaction
Lower metals don’t react
How to test a less reactive metal’s reactivity?
React with dilute acid at room temp
Potassium + sodium + lithium = dangerously explosive
Calcium = extremely rapid
Magnesium = rapid
Zinc = fairly rapid
Iron = slow
Copper = doesn’t react
What determines a metal’s reactivity?
Their ability to lose electrons and form positive ions
How does the reactivity change in group 1 metals?
As you go down the group = more reactive
Further down = more shells
More shells means less electrostatic attraction between nucleus and the reacting electron
Therefore it’s easier for the electron to react
How to extract metal from metal oxides?
Using displacement reactions
Why do we use carbon to extract metals?
It’s cheap
If the metal is less reactive than carbon eg zinc, iron and copper
Example of extracting metal
Carbon + iron oxide —> carbon dioxide + iron
What elements are reduced and oxidised in terms of oxygen when extracting metals?
More reactive element eg carbon displaces the less reactive metal from its oxide compound
It is therefore oxidised
Metal removed from its metal oxide compound so it’s reduced
Oxidation in terms of electrons
Losing electrons
Reduction in terms of electrons
Gaining electrons
How to find what elements have been reduced or oxidised (electrons) in an equation?
Write the symbol equation
Write the ions part of each compound
Compare them to before and after the reaction happens
Acids
pH below 7
Produce H+ ions when dissolved in water
Examples of acids
Hydrochloric acid
Sulfuric acid
Nitric acid
Formula for hydrochloric acid
HCl
Formula for sulfuric acid
H₂SO₄
Formula for nitric acid
HNO₃
Reacting acids and metals
Acid + metal —> salt + hydrogen
Displacement in terms of metals and acids reaction
More reactive metals than hydrogen displace the hydrogen in an acid
So copper doesn’t react
What determines the rate of an acid metal reaction?
How more reactive a metal is compared to hydrogen
Therefore iron with an acid would be a slow reaction
Acid metal redox reactions in terms of electrons
Metal is oxidised because it loses electrons to join with the salt
Hydrogen is reduced because it gains the electrons from the metal to become hydrogen atoms
Is acid and metal a neutralisation reaction?
NO it is a redox and displacement reaction
Redox reaction
= both oxidation and reduction happening at the same time
Base
Chemicals that neutralise acids
Produce OH- ions in dissolved water
pH above 7
Examples of bases
Metal oxides, metal hydroxides
Alkalis
Special type of base that can dissolve in water
Acid + base/alkali neutralisation
Acid + base —> salt + water
Making a copper salt
Copper itself doesn’t react with dilute acids so we use copper oxides or carbonates
Making a sodium/lithium/ potassium salt
Too dangerous to react with the metal on its own
We react it with a metal oxide or carbonate
What shows a neutralisation has happened?
H⁺ + OH⁻ —> H₂O
How does a neutralisation happen?
H+ from the acid and OH- from the base form H2O
Identifying salts
Contains a negative ion from the acid eg Cl-
Contains positive ion from base eg Na+
Makes:
NaCl
Acid and metal carbonate reaction
Acid + metal carbonate —> salt + water + carbon dioxide
What determines a strong or weak acid?
Whether it fully ionises in water = strong acid
Whether it partially ionises in water = weak acid
How can we tell if an acid only partially ionises?
Some hydrogen molecules in the compound don’t become H+
Or it’s a reversible reaction
Concentrated acid
More acid molecules than water in a given volume
Dilute acid
Less acid molecules than water in a given volume
Strong acid in a dilute concentration
Fully ionising
But less H+ ions as a result of the water than if it was a concentrated solution
Therefore high pH
Strong acid in a concentrated solution
Fully ionising
More H+ ions as there’s more acid molecules than water
Therefore lower pH
Weak acid in a dilute solution
Partially ionising
Therefore not many H+ ions and there’s even less because there’s more water
Therefore higher pH
Weak acid in a concentrated solution
Partially ionising
Not many H+ ions but slightly more because there’s more acid molecules than water
Therefore slightly lower pH than in a dilute solution
What determines the pH of an acid?
How many H+ ions there are when dissolved in water in a given volume
More H+ ions = lower pH
Less H+ ions = higher pH
If you decrease the pH by 1 how does that effect the number of H+ ions
X10 ions
One order of magnitude
