C-4 Chemical changes
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• What are acids
• Produce hydrogen ions in aqueous solutions - Ph less than 7
What are alkalis
• Aqueous solutions of alkalis contain hydrogen oxides - Ph more than 7
How can PH be measured
• Is the measure of acidity or alkalinity • Measured using universal indicator or PH probe • PH probe- electronic • Indicator- dyes
What happens in neutralisation in acids and bases
• Hydrogen ions react with hydroxide ions to produce water • Neutralisation0 acid + base – salt + water H+ + OH- – H2O (I)
• What is a strong acid
• Completely ionised in aqueous solution • All acid particles dissociate • Hydrochloric, nitric and sulphuric • faster reactions
What is a weak acid
• Do not fully ionise, in aqueous solutions - Ethanoic, citric and carbonic
What effect does concentration have on strength of acid
• The higher the concentration, the stronger the Ph - As Ph decreases by 1, hydrogen ion concentration increases by factor of 10
• What do acids do with metals
• Acids react with some metals to produce salts an hydrogen
What is a redox reaction
• Redox reactions are displacement reactions • A more reactive metal will displace a less reactive • Always metal own that gains electrons
What are alkalis
• Bases that dissolve water
• What do metal oxides and metal hydroxides and react with water to make
• Form a salt and water
What do acids and metal carbonates produce
• Metal carbonates are bases - react with acids to product salts
How are soluble salts made
• Using insoluble base • Pick right acid and base • Warm flute acid on burner then turn off • Add insoluble base bit at a time, tunnel none reacts. • Filter out excess solid • Warm using water bath or heater ti evaporate water, cool. Crystals form
What is the reactivity series
• Metals in order of reactivity • how easily they lose electrons • Higher up, faster and easier it reacts with water
What is the order in reactivity series
• Potassium • Sodium • Lithium • Calcium • Magnesium • Carbon • Zinc • Iron • Hydrogen • Carbon
What does how metals react tell you about reactivity
More reactive means faster the rate.
What is metal extraction
• Lots of metals react with oxygen to make oxides • Oxidiation • Form ores
How does metal extraction take place from ores
• Reduction reaction
What is a formation of ore reaction
• Oxidation • 2MG + O2 - 2MGO • Magnesium
What is the formulation for extraction of metal from ore
• Reduction • Copper 2CuO + C – 2Cu + CO2
How can metals be extracted buy carbon use
• Chemical • Some metals • Carbon gains the oxygen that is lost from reduction e.g - iron 2Fe2O3 + 3C – 4Fe + 3CO2
What determines wether or not a metal can be extracted by carbon
If its less reactive than carbon so it can displace it - If not electrolysis is used
What does electrolysis mean
• Splitting up with electrolysis
• What happens within electrolysis
• Electrical current is passed through molten for dissolved ionic compound • Positive ions move towards cathode - gain electrons - reduced • Negative ions, move towards anode - lose electrons oxides