Chemical Changes Flashcards
(22 cards)
Define oxidation and reduction in terms of oxygen.
Oxidation - metal gained oxygen.
Reduction - metal lost oxygen.
Define oxidation and reduction in terms of electrons.
OIL RIG
Oxidation Is Loss, Reduction is Gain
What does an acid + metal form?
salt + water
What does an acid + alkali form?
salt + water
What does an acid + base form?
salt + water
What does an acid + metal carbonate form?
salt + carbon dioxide + water
Name 3 acids and their formula?
Hydrochloric acid - HCL
Sulphuric acid - H2SO4
Nitric acid - HNO3
What ion is responsible for acidity and alkalinity?
Acidity: Hydrogen ion - H+
Alkalinity: OH-
What is the pH of acids, alkalis and neutral and colours on the pH scale?
Alkali - blue to purple, pH 1-6
Acids - red to orange to yellow, pH 8-14
Neutral - green, pH 7
What 2 methods can you do to test for pH?
Using universal indicator or a pH probe.
What metals can be extracted from their ores using carbon?
Metals such as zinc, iron and copper.
What metals have to be extracted from their ores by electrolysis?
Metals that are more reactive than carbon.
What is a strong acid?
Completely ionised in aqueous solution.
What is a weak acid?
Partially ionised in aqueous solution.
How does the strength of an acid relate to pH?
Stronger the acid, lower the pH.
What is the relationship between pH and hydrogen ion concentration?
As concentration of H+ ions increases by a factor of 10, the pH value decreases by 1.
What happens during electrolysis?
Passing an electric current through the electrolyte causes the ions to move to the electrodes.
+ cathodes go to the cathode.
- cathodes go to the anode.
Ions are discharged at the electrodes to form elements.
Does electrolysis require a lot of energy?
Large amounts of energy are used in the extraction process.
Why is a mixture used in the electrolysis of aluminium oxide?
Aluminium oxide has a very high melting point, when in a mixture, the melting point is reduced.
Why must the positive electrode be constantly replaced in the electrolysis of aluminium oxide?
Because oxygen forms there and reacts with the hot carbon, gradually the carbon anode burns away and needs to be replaced regularly.
How can you predict what forms at the anode for electrolysis of aqueous solutions?
Oxygen is produced unless solution contains halide ions when halogen is produced.
How can you predict what forms at the cathode for electrolysis of aqueous solutions?
Hydrogen is produced if the metal is more reactive than hydrogen.
