OCR A Chemistry – 5.2.2 Entropy and ∆G

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• the more disordered a system is, the greater its entropy value is.

• liquid generally has a greater entropy than gas

• entropy is the measure of dispersal of energy in a system

If a reaction produces more gaseous moles than was in the starting materials, there will be [?] in entropy

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There is usually an increase in entropy when...

• a solid is dissolved in solution

• a solid salt is formed

• the products contain more gaseous moles than the reactants

• an alkene is hydrogenated

• a liquid boils

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an increase in entropy is ...

• always involved for decomposition of a solid

• always involved two solids reacting

• always bigger when CO₂(g) is formed instead of H₂(g)

• bigger when the balanced equation shows more gaseous moles are formed

What is the correct sign for ∆S and the best explanation for this sign?

H₂O(l) → H₂O(g)

• +ve, gas from a liquid

• –ve, more moles of gas in the products side

• +ve, more disorder

• –ve, less disorder

TICK ALL CORRECT STATEMENTS

at 1 atm pressure, ice melts into water

• ∆H is positive

• ∆S is positive

• ∆G is positive

• there are hydrogen bonds present in liquid water

TICK ALL USEFUL STATEMENTS: to calculate ∆_rS^⊖...

• ΣS^⊖(products) – ΣS^⊖(reactants)

• ΣS^⊖(reactants) – ΣS^⊖(products)

• ignore stoichiometries in the reaction equation

• convert final answer to kJ mol^–1 for use in further calculations

TICK ALL THAT APPLY : if a reaction is feasible...

• it still may not occur because of its activation energy

When a reaction becomes feasible, ΔG =

What is y?

Δy = Δc − TΔm