C5 - Energy Changes PART 1
created 2/12/17
- Created by: amphibology
- Created on: 02-12-17 11:28
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- Exothermic
- Combustion
- Neutralisation
- More common
- Ways to reduce energy loss
- Into a polystyrene container
- Mix the reagents
- Measure temperature before + after
- Mix the reagents
- Neutralisation, metals + acid reactions, carbonate + acid reactions
- Mass + concentration of reactants
- Place 25cm(3) of HCl & NaOH (0.25 mol/dm(3)
- Place in 25C water bath until set to same temperature
- Put HCl into the cup (lid + cotton wool outside)
- Add NaOH
- Check temp every 30 seconds
- MAKE NOTE OF HIGHEST TEMP.
- Into a polystyrene container
- Bond breaking
- Combustion
- Endothermic
- Thermal decomposition
- Citric Acid + Sodium hydrogencarbonate
- Bond forming
- Repeat with different conc.
- 0.5 mol/dm(3)
- 1 mol/dm(3)
- Reaction Profiles
- Exothermic
- Initial rise - activation energy
- Fall BELOW reactant energy line - ENERGY RELEASED
- Initial rise - activation energy
- Endothermic
- Initial rise - activation energy
- Fall ABOVE reactant energy line - ENERGY ABSORBED
- Initial rise - activation energy
- Exothermic
- Bond energy
- Overall energy charge (kJ/mol) =
- Ratio is the same so can't compare!
- (strong + strong bonds) vs. (weak + weak bonds)
- CELLS AND BATTERIES
- Electrochemical cells
- Two electrodes, & an electrolyte
- Usually metal electrolyte;
- Has to conduct electricity
- Electrochemical cells
- Two electrodes, & an electrolyte
- Usually metal electrolyte;
- Has to conduct electricity
- Liquid
- Has to conduct electricity
- Usually metal electrolyte;
- Two electrodes, & an electrolyte
- Electrochemical cells
- Liquid
- Has to conduct electricity
- Usually metal electrolyte;
- Two electrodes, & an electrolyte
- Electrochemical cells
- Charge difference caused by chemical reactions
- If electrodes connected by wire
- Charge can flow
- Electricity is produced
- Charge can flow
- If electrodes connected by wire
- Reactivity difference between electrodes is **directly proportional** to voltage - potential difference
- Electrolyte also affects size of voltage
- Ions will react differently
- 2 or more cells
- In SERIES
- BATTERIES
- VOLTAGE is combined
- In SERIES
- Non-rechargeable batteries
- Chemical reactions: irreversible
- e.g. alkaline batteries
- RECHARGEABLE batteries
- External electric current
- Reaction is reversed
- Hydrogen-oxygen fuel cells
- Produces water & electricity
- REDOX reaction
- Electrolyte - usually potassium hydroxide
- Electrodes - porous carbon, w/ a catalyst
- Hydrogen - Anode compa.
- Oxygen - Cathode com.
- Electrodes - porous carbon, w/ a catalyst
- Oxidises
- Electric current flows through external circuit
- From anode to cathode
- Conventional fuels - petrol
- Batteries
- Fuel cells
- Hydrogen: fossil fuels :(
- Less pollutants
- Not made from highly toxic metal compounds - disposal
- Less energy, less expensive
- Fuel cells
- Batteries
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