C-4 Chemical changes Flashcards
- 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
How can electrolysis be used to extract ores
- Expensive
- Molten
- Sperated
