Question 1

Marks: 1

Which row correctly describes a reaction that only occurs spontaneously at a low temperature?

	Reaction	ΔH_reaction
A.	X (g) + Y (g) → Z (g)	exothermic
B.	R (s) →T (g) + U (g)	endothermic
C.	E (g) → 3F (g)	endothermic
D.	M (g) + 2N (g) → P (g) + Q (g)	endothermic

Key Concepts

Spontaneous Reactions

Question 2

Marks: 1

Urea reacts with water to produce carbon dioxide and ammonia via the following reaction

CO(NH₂)₂ (aq) + H₂O (l) → CO₂ (g) + 2NH₃ (g) ΔH = 133 kJ mol^-1

Thermodynamic data for the components of this reaction are

Substance	CO(NH₂)₂ (aq)	H₂O (l)	CO₂ (g)	NH₃ (g)
S^ꝋ (J K^-1 mol^-1)	105	70	214	192

At which of the following temperatures will this reaction become feasible?

$\frac{133}{[214 + (2 \times 192)] - (105 + 70)}$
$\frac{[214 + (2 \times 192)] - (105 + 70)}{133}$
$133 - \frac{[214 + (2 \times 192)] - (105 + 70)}{1000}$
$\frac{133 \times 1000}{[214 + (2 \times 192)] - (105 + 70)}$

Key Concepts

Spontaneous Reactions

Question 3

Marks: 1

Which reaction occurs with the largest increase in entropy?

Pb(NO₃)₂ (s) + 2KI (s) → PbI₂(s) + 2KNO₃ (s)
CaCO₃ (s) → CaO (s) + CO₂ (g)
3H₂ (g) + N₂ (g) → 2NH₃ (g)
H₂ (g) + I₂(g) → 2HI(g)

Key Concepts

Predicting Entropy Changes

Question 4

Marks: 1

Which is correct for the reaction H₂O (g) → H₂O (l)?

Enthalpy increases and entropy increases.
Enthalpy decreases and entropy increases.
Enthalpy increases and entropy decreases.
Enthalpy decreases and entropy decreases.

Key Concepts

Entropy
Exothermic & Endothermic

Question 5

Marks: 1

Which factors will increase the entropy of this system?

CaCO₃ (s) $⇌$ CaO (s) + CO₂ (g)

I. Increasing the temperature without changing the volume of the container.

II. Decreasing the concentration of the gas without changing the volume of the container.

III. Increasing the pressure without changing the volume of the container.

I and II only
I and III only
II and III only
I, II and III

Key Concepts

Entropy
Le Chatelier's Principle

DP IB Chemistry: HL

Topic Questions

15.2 Entropy & Spontaneity

Question 1

Key Concepts

Question 2

Key Concepts

Question 3

Key Concepts

Question 4

Key Concepts

Question 5

Key Concepts

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