Energetics Flashcards
(27 cards)
What’s the enthalpy change of a reaction? (2)
- The heat change in a reaction (1)
- At constant pressure (1)
What are the standard conditions? (2)
- 100kPa pressure (1)
- 298K (1)
What’s an endothermic reaction + Example ? (3)
- Reaction that absorbs energy from it’s
surroundings (1) - Positive enthalpy change (1)
- Thermal decomposition (1)
What’s an exothermic reaction + Example? (3)
- Reaction that releases energy to it’s
surroundings (1) - Negative enthalpy change (1)
- Combustion of ethene (1)
What are the 4 types of enthalpy change? (4)
- Standard enthalpy change of reaction (1)
- Standard enthalpy change of formation (1)
- Standard enthalpy change of
neutralisation (1) - Standard enthalpy change of combustion
(1)
What is the standard enthalpy change of combustion? (3)
- The enthalpy change when one mole of a
substance is completely burned in oxygen
(1) - To make CO2 and H2O (1)
- Under standard conditions (1)
What is the standard enthalpy change of neutralisation? (3)
- The enthalpy change when an acid and
alkali react (1) - To form one mole of water (1)
- Under standard conditions (1)
What is the standard enthalpy change of formation? (3)
- The enthalpy change when one mole of a
compound is formed (1) - From its elements in standard condition (1)
- Under standard conditions (1)
What is the standard enthalpy change of reaction? (3)
- The enthalpy change of a reaction (1)
- According to the molar quantities in the
equation (1) - Under standard conditions (1)
What happens to bonds in endothermic reactions? (2)
- More energy is needed to break the bonds
(1) - Than energy given out when bonds are
formed (1)
What happens to bonds in exothermic reactions? (2)
- More energy is released when bonds are
formed (1) - Than what is needed to break initial bonds
(1)
How is the enthalpy change of combustion worked out? (3)
- Calorimetry (1)
- Temperature of water is raised to a
specific amount (1) - With the mass of fuel measured before
and after (1)
How is energy transferred calculated? (4)
- Q = mcΔT (1)
- In J, g and K (1)
- Enthalpy = q/moles (1)
- In kJMol-1 (1)
How is heat loss reduced in calorimetry? (3)
- Polystyrene cup (1)
- Lid (1)
- Wind shield prevents flame draught (1)
How is calorimetry used for neutralisation? (2)
- Add acid and measure temperature (1)
- Add alkali, stir and measure temperature
change (1)
How do you draw the hess’s cycle of formation? (2)
- Reaction at the top (1)
- Enthalpy of formation arrows pointing up (1)
What do the arrows indicate on the born Haber cycle? (2)
- Arrow down = Exothermic
- Arrow up = Endothermic
Explain all enthalpy in the born Haber cycle (5)
Left side:
- ΔfH pointing down (1)
- 2 ΔatH pointing up (1)
- Δie1H pointing up (1)
Right Side:
- Δea1H pointing down (1)
- ΔlatticeH pointing down (1)
Explain born Haber of LiCl(s)
(6)
Left side:
- Li(s) + 1/2 Cl2 (g)
- Li(s) + Cl(g)
- Li(g) + Cl(g)
- Li+(g) + Cl(g) + e-
Right side:
- Li+(g) + Cl-(g)
- LiCl(s)
How do you work out enthalpy change of solution? (3)
Hess’s cycle:
- ΔdissH is left arrow pointing down (1)
- ΔhydH is right arrow pointing up (1)
- ΔsolutionH pointing across (1)
What affects enthalpy change of hydration? (3)
- Higher charge or smaller size ion (1)
- Stronger electrostatic attraction (1)
- More exothermic enthalpy of hydration (1)
What is entropy? (2)
- Measure of disorder (1)
- E.G. Gas has higher entropy than solid (1)
What makes a reaction entropically favourable (2)
- More moles on the product side (1)
- Going from solids to liquid/gas (1)
How do you work out entropy feasibility in a system? (2)
ΔS = Sproducts - Ssurroundings (1)
Positive = Feasible (1)
