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WorksheetsOCR A Chemistry – 5.2.2 Entropy and ∆G
Total questions: 19
Worksheet time: 11mins
TICK ALL THAT APPLY
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
(a)
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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 will have a ∆G < 0
it will have a ∆G ≤ 0
it still may not occur because of its activation energy
it will have ∆S ≥ 0
When a reaction becomes feasible, ΔG =
(a)
What is y?
Δy = Δc − TΔm
(a)
What is c?
Δy = Δc − TΔm
(a)
What is m?
Δy = Δc − TΔm
(a)
TICK ALL THAT APPLY
ΔG = ΔH − TΔS
(y = c + xm)
The units of T are in K
The units of y will be the same as the units of c
The units of S will always come out in kJ K–1 mol–1
a graph of y vs T will give –ΔS as the gradient
a graph of y vs T will give –Δc as the y-intercept
Are you ready to try some exam-ples?
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Which reaction involves an overall increase in entropy
C2H2(g) + 2H2(g) → C2H6(g)
NH4Cl(s) + aq → NH4Cl(aq)
4Na(s) + O2(g) → 2Na2O(s)
2CH3OH(l) + 3O2(g) → 2CO2(g) + 4H2O(l)
Which reaction represents the largest change in entropy?
Al2(CO3)3(s) → Al2O3(s) + 3CO2(g)
BaO(s) + C(s) → Ba(s) + CO(g)
CaCO3(s) → CaO(s) + CO2(g)
Li(s) + HCl(aq) → LiCl2(aq) + ½H2(g)
0.165 J K–1 mol–1
0.165 kJ K–1 mol–1
165 kJ K–1 mol–1
263 J K–1 mol–1
CaO(s) + C(s) → Ca(s) + CO(g)
∆S = 193.6 J K–1 mol–1
∆H = 525 kJ mol–1
The reaction does not occur easily. What temperature does the reaction become feasible?
2.7 K
2.7 °C
2439 °C
2712 °C
6CO2(g) + 6H2O(l) → C6H12O6(s) + 6O2(g)
∆rH = +2879 kJ mol–1, T = 25 °C
∆rS = –256 J K–1 mol–1
∆rG = ? kJ mol–1
+2890
+2955
+79200
+2814
