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DP IB Chemistry: SL

Topic Questions

Home / IB / Chemistry: SL / DP / Topic Questions / 5. Energetics / Thermochemistry / 5.3 Bond Enthalpy / Multiple Choice: Paper 1


5.3 Bond Enthalpy

Question 1

Marks: 1

In the gas phase, phosphorus pentachloride can be thermally decomposed into gaseous phosphorus trichloride and chlorine.

PCl→ PCl3 + Cl2

The table below gives the relevant bond energies found in these compounds.

bond

bond energy / kJ mol–1

P–Cl (in both chlorides)

Cl–Cl

x

y

What is the enthalpy change in the decomposition of the reaction?

  • y minus 2 x

  • 2 x minus y

  • 8 x plus y

  • x plus y

Choose your answer
  

Question 2

Marks: 1

Which equation correctly shows how the bond energy for the covalent bond Y–Z can be calculated by dividing ΔH by n?

  • nYZ(g) → nY(g) +begin mathsize 16px style n over 2 end style Z2(g)

  • Z(g) + YZn-1(g) → YZn(g)

  • 2YZn (g) → 2YZn-1(g) + Y2(g)

  • YZn(g) → Y(g) + nZ(g)

Choose your answer
  

Question 3

Marks: 1

The diagram shows the skeletal formula of cyclobutane.
 q3_5-3_mcq_hard_ib-chemistry-sl

The enthalpy change of formation of cyclobutane is +75.1 kJ mol–1, and the enthalpy change of atomisation of graphite is +712 kJ mol–1.

The bond enthalpy of C–H is 414 kJ mol–1 and of H–H is 436 kJ mol–1.

What is the average bond enthalpy of the C–C bond in cyclobutane?

  • 712 blank minus 436 plus 2 left parenthesis 414 right parenthesis plus fraction numerator 75.1 over denominator 4 end fraction

  • 712 blank plus 436 minus 414 minus fraction numerator 75.1 over denominator 4 end fraction

  • 712 blank plus 436 minus 2 left parenthesis 414 right parenthesis minus fraction numerator 75.1 over denominator 4 end fraction

  • 712 blank plus 436 minus 2 left parenthesis 414 right parenthesis minus 75.1

Choose your answer
  

Question 4

Marks: 1

Butane can be produced by the hydrogenation of buta-1,3-diene.

C4H6 (g) + 2H2 (g) → C4H10 (g)                 ΔH = -248 kJ mol-1

Bond

C-C

C-H

H-H

Mean bond enthalpy / kJ mol-1

346

414

436

Using the information, which calculation shows the bond enthalpy for the C=C bond in buta-1,3-diene?

  • -248 - ( 2 x 436) + (2 x 346) + (4 x 414)

  • -124 - 436 + 346 + (2 x 414)

  • (2 x 346) + (4 x 414) + 248 - (2 x 436)

  • 346 + (2 x 414) + 124 - 436

Choose your answer
  

Question 5

Marks: 1

The equations to form methane and propane from their gaseous atoms are:

C (g) + 4H (g) → CH4 (g)              ΔHr = -1656 kJ mol-1

3C (g) + 8H (g) → C3H8 (g)           ΔHr = -4004 kJ mol-1

What is the bond enthalpy of a C-C bond?

  • begin mathsize 16px style fraction numerator negative 4004 blank plus blank 2 blank cross times blank left parenthesis 1656 right parenthesis over denominator 3 end fraction end style

  • 2002 - 1656

  • 1656 - 2002

  • begin mathsize 16px style fraction numerator negative 4004 blank minus blank 2 blank cross times blank left parenthesis 1656 right parenthesis over denominator 3 end fraction end style

Choose your answer
  

Question 6

Marks: 1

Ultraviolet radiation is split into three regions:

  • UV A (wavelength 400 - 320 nm)
  • UV B (wavelength 320 - 280 nm)
  • UV C (wavelength < 280 nm)

High energy photons are present in the solar spectrum at high altitude. The maximum wavelength of a photon that has enough energy to break the O=O bond in oxygen is 240 nm, which is in the UV C region of ultraviolet radiation..

The energy per mole required to break an O=O bond can be calculated using the following equation:

 begin mathsize 16px style fraction numerator B o n d blank e n e r g y blank p e r blank m o l e over denominator A v o g a d r o apostrophe s blank c o n s t a n t end fraction end style= Energy per bond

Using the supplementary equations c = νλ and E = hν, which is the correct calculation to determine the bond energy of an O=O in kJ mol-1?

Avogadro’s constant = 6.02 x 1023

Planck’s constant = 6.63 x 10-34 J s

Speed of light = 3.00 x 108 m s-1

  • begin mathsize 16px style fraction numerator 6.63 blank cross times blank 3.00 blank cross times blank 6.02 blank cross times blank 10 over denominator 2.4 end fraction end style

  • fraction numerator 6.63 blank cross times blank 3.00 blank cross times blank 6.02 blank cross times blank 10 to the power of 4 over denominator 2.4 end fraction

  • begin mathsize 16px style fraction numerator 6.63 blank cross times blank 3.00 blank cross times blank 6.02 blank cross times blank 10 to the power of negative 3 end exponent over denominator 2.4 end fraction end style

  • begin mathsize 16px style fraction numerator 6.02 blank cross times blank 2.4 blank cross times blank 10 to the power of 42 over denominator 6.63 blank cross times blank 3.00 blank end fraction end style

Choose your answer
  

Question 7

Marks: 1

Which of the following statements about the average bond enthalpy of the halogens are correct?

  1. Fluorine has the highest average bond enthalpy
  2. Average bond enthalpy generally decreases as the size of the atoms increases
  3. In general, increased shielding results in a lower bond enthalpy
  • I and II only  

  • I and III only  

  • II and III only 

  • I, II and III

Choose your answer
  

Question 8

Marks: 1

What is the correct order to show the decreasing strength of the F-H, N-H and O-H bonds?

  • N-H > O-H > F-H 

  • O-H > N-H > F-H

  • F-H > N-H > O-H 

  • F-H > O-H > N-H 

Choose your answer
  

Question 9

Marks: 1

Water has two different bond enthalpies for the two O-H bonds that it contains:

H2O (g) → H (g) + OH (g)             ΔH = +502 kJ mol-1

OH (g) → H (g) + O (g)                 ΔH = +427 kJ mol-1

The average O-H bond enthalpy from an accepted data table is 463 kJ mol-1.

Which calculation correctly shows the percentage difference between the average O-H bond enthalpy of water and the data table average bond enthalpy value?

  • 100 divided by open parentheses fraction numerator 502 blank plus blank 427 over denominator 2 blank cross times blank 463 end fraction minus 1 close parentheses

  • 100 cross times open parentheses fraction numerator 502 blank plus blank 427 over denominator 2 blank cross times blank 463 end fraction minus 1 close parentheses

  • 100 cross times open parentheses fraction numerator 2 blank cross times blank 463 over denominator 502 blank plus blank 427 end fraction minus 1 close parentheses

  • 100 cross times open parentheses fraction numerator 502 blank plus blank 427 over denominator 2 blank cross times blank 436 end fraction minus 1 close parentheses

Choose your answer
  

Question 10

Marks: 1

Some of the reactions involved in the formation and depletion of ozone are:

  1. O2 → 2O
  2. O2 + O → O3
  3. O3 + O → 2O2

Which reactions are exothermic?

  • I and II only  

  • I and III only  

  • II and III only 

  • I, II and III

Choose your answer