Topic 4 - Chemical changes Flashcards
What is reduction and oxidation?
Reduction:
— Loss of oxygen
Oxidation:
— Gain of oxygen
What is the order of the reactivity series from most to least reactive? And the mnemonic.
- Potassium (Please)
- Sodium (Stop)
- Calcium (Calling)
- Magnesium (Me)
- Aluminium (A)
- Carbon (Careless)
- Zinc (Zebra)
- Iron (Instead)
- Tin (Try)
- Lead (Learning)
- Hydrogen (How)
- Copper (Copper)
- Silver (Saves)
- Gold (Gold)
What is the equation if you react a metal with an acid or a metal with water?
Metal + acid —> salt + hydrogen
Metal + water —> metal hydroxide + hydrogen
How would you extract metal more and less reactive than carbon in the reactivity series?
Metals more reactive than carbon are extracted using electrolysis and metals less reactive than carbon are extracted by reduction using carbon.
Define oxidation and reduction in terms of electrons.
Oxidation Is Loss of electrons Reduction Is Gain of electrons
(REVISE HALF EQUATIONS AND IONIC EQUATIONS)
What is the equation when a metal oxide, metal hydroxide or metal carbonate reacts with an acid?
Metal oxide / Metal hydroxide + acid —> salt + water
Metal carbonate + acid —> salt + water + carbon dioxide
What is the use of universal indicator?
To measure an estimate for the pH of a solution
What ions do acids and alkalis produce? Where are acids and alkalis on the pH scale?
Acids produce H+ ions and alkalis produce OH- ions.
An acid is found anywhere before the number 7 of the pH scale. An alkali is found after the number 7 and a neutral solution has a pH value of 7.
What is the equation for a neutralisation reaction?
Acid + base —> salt + water
What are titrations used for?
Titrations are used to find out how much acid is needed to neutralise a volume of alkali.
(TITRATION PRACTICAL)
What is the difference between a strong and weak acid? How does the hydrogen ion concentration change in relation to the pH scale?
A strong acid completely ionises in water whereas a weak acid partially ionises in water. Examples of strong acids are hydrochloric, sulfuric and nitric acids. Exampless of weak acids are ethanoic, citric and carbonic acids.
As the pH decreases, the hydrogen ion concentration increases.
What is the formula for hydrochloric acid, sulfuric acid and nitric acid?
- – Hydrochloric acid: HCl
- – Sulfuric acid: H2SO4
- – Nitric acid: HNO3
Define electrolysis and electrolyte
Electrolysis:
— The process of breaking down molten or dissolved ionic substances using electricity
Electrolyte:
— A liquid or solution that contains free ions therefore it can conduct electricity.
During electrolysis of a molten substance, where do the positive and negatively charged ions go?
The positively charged ions move towards the cathode and negatively charged move towards the anode.
E.g. lead bromide: lead moves towards the cathode as it is a metal and has positively charged ions, bromine moves towards the anode as it is a non-metal and contains negatively charged ions
How is aluminium extracted from its ore bauxite by electrolysis and why is cryolite used?
— Aluminium oxide has a high melting point so cryolite is used to lower its melting point to reduce the amount of energy required to extract aluminium.
— The molten mixture contains free ions so it can conduct electricity. The positively charged aluminium ions move towards the cathode and gain three electrons to form an aluminium atom. Then the oxygen ions move towards the anode and lose two electrons to form an oxygen atom.
