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Chemistry
Energetics
Question | Answer |
---|---|
Define endothermic process | Energy is absorbed into the system which results in bond breaking |
Define exothermic process | Energy is released from the system which results in bond making |
Why is enthalpy +ve in endothermic reactions | The heat change in product is greater than heat change in reactant Hp>Hr |
Why is enthalpy -ve in exothermic reactions | The heat change in reactant is greater than heat change in product Hr>Hp |
Does temp of surroundings increase/decrease in endothermic reactions | Decrease due to heat being absorbed |
Does temp of surroundings increase/decrease in exothermic reactions | Increase due to heat being released |
Why is Ea higher in endothermic reactions | Great amount of energy needs to be absorbed to allow for bond breaking hence there are fewer endothermic reactions |
Definition of bond energy and its unit | The amount of energy needed to break 1 mole of a particular bond in 1 mole of a gaseous molecule KJ/mol |
What effect does the type of bond have on bond energy | As the bonds between atoms increase, bond energy increases single bond<double bond<triple bond |
What effect does the bond length have on bond energy | If bond length increase, bond energy decreases |
T/F. Bond length increases because atomic radius increases | T |
Formula for enthalpy change | delta h = sum of reactants - sum of formed |
How does ionic charge affect magnitude of lattice energy | The higher the ionic charge of the ions the more attraction between the ions in the compound therefore latt energy is greater |
State Hess' Law | The total enthalpy change of a reaction is independent of the route the reaction proceeds. |