Question 1

Marks: 1

The standard enthalpy change, ΔH^Ө, for the following reaction is -246 kJ.

N₂(g) + 3F₂(g) → 2NF₃(g)

The bond energy of N≡N is 945 kJ mol^-1 and F–F is 159 kJ mol^-1

What is the bond energy of the N–F bond?

$\frac{246 - (945 + (3 \times 159))}{6}$
$\frac{- 246 + (945 + (3 \times 159))}{6}$
$\frac{246 + (945 + (3 \times 159))}{6}$
$246 + (945 + (3 \times 159))$

Question 2

Marks: 1

The complete combustion of ethyne, C₂H₂, is shown in the equation below.

H−C≡C−H + 2½ O═O → H−O−H + 2O═C═O

Using the average bond enthalpies given in the table, what is the enthalpy change of combustion of ethyne?

bond	average bond enthalpy / kJ mol^-1
C−H	a
C≡C	b
O═O	c
C═O	d
O−H	e

$(2 e + 4 d) - (2 a + b + 2 ½ c)$
$(2 a + b + 2 ½ c) - (- 2 e - 4 d)$
$(2 a + b + 2 ½ c) - (2 e + 4 d)$
$- e - d + (2 a + b + 2 ½ c)$

Question 3

Marks: 1

Compound R into compound T, it was found that the reaction proceeded by way of compound S, which could be isolated. The following steps were involved.

R → S; ΔH is positive

S → T; ΔH is negative

Which reaction profile fits these data? q3_5-3_ib_sl_easy_mcq

Question 4

Marks: 1

The reaction pathway for an endothermic reaction is shown. q4_5-3-ib_sl_medium_mcq

Which arrow represents the activation energy for the reverse reaction?

Question 5

Marks: 1

The reaction pathway shows the energies of the reactants, the products and the transition state of a reaction. q5_5-3_ib_sl_medium_mcq

Which expression correctly represents how to calculate the activation energy of the forward reaction?

E₃ – E₂
E₂ – E₁
E₂ – E₃
E₁ – E₂

Question 6

Marks: 1

The incomplete combustion of methanol can produce carbon monoxide and water:

q6_5-3_ib-sl_medium_mcq

Some enthalpy data is given in the table.

	C-H	C-O	O-H	O=O	C=O
Mean bond dissociation enthalpy / kJ mol⁻¹	414	358	463	498	804

What is the enthalpy change for this incomplete combustion of methanol?

(414 + 358 + 463 + 498) - (463 + 804)
(4 x 463 + 804) - (3 x 414 + 358 + 463 + 498)
(4 x 414 + 358 + 498) - (4 x 463 + 804)
(3 x 414 + 358 + 463 + 498) - (4 x 463 + 804)

Question 7

Marks: 1

Which of the following statements about bond enthalpy are true?

A bond enthalpy may be inaccurate when compared to data tables because it is not an average value
Average bond enthalpies are valid for all states of matter
Bond enthalpies may be inaccurate as they do not account for intermolecular forces

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

Question 8

Marks: 1

Four possible reactions (A, B, C and D) of the following equation are measured at the same temperature.

X (g) + Y (g) → Z (g)

Which reaction pathway diagram shows the reaction occurring rapidly with an overall negative enthalpy value? q8_5-3_ib_sl_medium_mcq

Question 9

Marks: 1

Which combination about bond breaking and bond formation energy changes is correct?

	Bond breaking	Bond formation
A	endothermic	endothermic
B	endothermic	exothermic
C	exothermic	endothermic
D	exothermic	exothermic

Question 10

Marks: 1

Which reactions are involved in maintaining the concentration of ozone in the upper atmosphere?

O₃ → O₂ + O^●
O₂ → 2O^●
O₂ + O^● → O₃

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

DP IB Chemistry: SL

Topic Questions

5.3 Bond Enthalpy

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

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