0%

DP IB Chemistry: SL

Topic Questions

Home / IB / Chemistry: SL / DP / Topic Questions / 5. Energetics / Thermochemistry / 5.2 Hess's Law / Multiple Choice: Paper 1


5.2 Hess's Law

Question 1

Marks: 1

The first stage in the industrial production of nitric acid from ammonia can be represented by the following equation. 

4NH3(g)  +  5O2(g)  ⇌  4NO(g)  +  6H2O(g) 

Using the following standard enthalpy change of formation data, what is the value of the standard enthalpy change begin mathsize 14px style italic increment H to the power of italic ⦵ end style for this reaction?

Compound

 begin mathsize 14px style increment H subscript f superscript ⦵ end style/kJ mol– 1

NH3 (g)

-46.1

NO (g)

+90.3

H2O (g)

-241.8

  • begin mathsize 14px style left parenthesis 4 space cross times space left parenthesis negative 46.1 right parenthesis right parenthesis space plus left parenthesis left parenthesis 4 space cross times space 90.3 right parenthesis plus left parenthesis 6 space cross times space left parenthesis negative 241.8 right parenthesis right parenthesis space end style

  • begin mathsize 14px style left parenthesis left parenthesis 4 space cross times space 90.3 right parenthesis plus left parenthesis 6 space cross times space left parenthesis negative 241.8 right parenthesis right parenthesis space minus left parenthesis 4 space cross times space left parenthesis negative 46.1 right parenthesis right parenthesis end style

  • begin mathsize 14px style left parenthesis 4 space cross times space left parenthesis negative 46.1 right parenthesis right parenthesis space minus left parenthesis left parenthesis 4 space cross times space 90.3 right parenthesis plus left parenthesis 6 space cross times space left parenthesis negative 241.8 right parenthesis right parenthesis right parenthesis end style

  • begin mathsize 14px style left parenthesis negative 46.1 right parenthesis space minus left parenthesis 90.3 right parenthesis plus left parenthesis negative 241.8 right parenthesis end style

Choose your answer
  

Question 2

Marks: 1

Titanium occurs naturally as the mineral rutile, TiO2. One possible method of extraction of titanium is to reduce the rutile by heating with carbon. 

TiO2(s) + 2C(s)  →  Ti(s) + 2CO(g) 

The standard enthalpy changes of formation of TiO2(s) and CO(g) are –890 kJ mol-1 and –110.5 kJ mol-1 respectively. 

What is the standard enthalpy change of the extraction of titanium?

  • + 669 kJ mol–1

  • + 779.5 kJ mol–1

  • – 779.5 kJ mol–1

  • – 669 kJ mol–1

Choose your answer
  

Question 3

Marks: 1

The combustion of ethanol (C2H5OH) is increasingly being used to fuel cars. The combustion reaction is shown below 

                         C2H5OH(l)  +   3O2 (g)   →  2CO2(g)    +  3H2O(l) 

The standard enthalpy change of formation of carbon dioxide is a kJ mol–1.

The standard enthalpy change of formation of water is b kJ mol–1.

The standard enthalpy change of formation of ethanol is c kJ mol–1

What is the standard enthalpy change of combustion for ethanol?

  • 2a + 3b + c

  • 2a + 3b − c

  • −2a − 3b + c

  • −2a − 3b −c

Choose your answer
  

Question 4

Marks: 1

Propanone has the molecular formula C3H6O. Use the following information to calculate the enthalpy change for the formation of propanone? 

The enthalpy change of combustion of carbon is x kJ mol -1

The enthalpy change of combustion of hydrogen is y kJ mol -1

The enthalpy change of combustion of propanone is z kJ mol -1

  • x + y - z

  • 3x + 3y - z

  • z - 3x + 3y 

  • 3x + 3y + z

Choose your answer
  

Question 5

Marks: 1

Combustion of ethene proceeds via the reaction shown in the Hess cycle diagram.q5_5-2_ib_sl_medium_mcq

 What are the correct elements missing from the Hess cycle?

  • 2C (g) + 2H2 (g) + 3O2 (g)

  • C (s) + H2 (g) + O2 (g)

  • 2C (s) + 2H2 (g) + 3O2 (g)

  • C2 (s) + 2H2 (g) + 3O2 (g)

Choose your answer
  

Question 6

Marks: 1

Combustion of propene proceeds via the reaction shown in the Hess cycle diagram.q6_5-2_ib_sl_medium_mcq

Which are the correct labels for the enthalpies shown in the Hess cycle?

 

P

Q

R

S

A

ΔHӨc

ΔHӨr

ΔHӨc

ΔHӨc

B

ΔHӨc

ΔHӨf

ΔHӨr

ΔHӨr

C

ΔHӨc

ΔHӨf

ΔHӨc

ΔHӨf

D

ΔHӨr

ΔHӨr

ΔHӨf

ΔHӨf

    Choose your answer
      

    Question 7

    Marks: 1

    Hess’s Law can be used to calculate the enthalpy change for reactions that are difficult to measure experimentally, such as the conversion of graphite to diamond. 

    Which enthalpy data could be used to calculate the enthalpy change for the conversion of graphite to diamond? 

    1. Enthalpy of reaction
    2. Enthalpy of combustion
    3. Enthalpy of formation
    • I and II only

    • I and III only 

    • II and III only 

    • I, II and III

    Choose your answer
      

    Question 8

    Marks: 1

    A basic definition of Hess’s Law states that the overall enthalpy change for a reaction is the same independent of the route taken. 

    The addition of which of the following statements makes the definition of Hess’s Law more complete? 

    1. Providing that the reactants are the same
    2. Providing that the products are the same
    3. Providing that the conditions at the start and the end of the reaction are the same
    • I and II only 

    • I and III only 

    • II and III only 

    • I, II and III

    Choose your answer
      

    Question 9

    Marks: 1

    The hydration enthalpy of anhydrous copper(II) sulfate cannot be measured directly. It can be found indirectly by determining the solution enthalpies of anhydrous and hydrated copper(II) sulfate. q9_5-2_mcq_medium_ib-chemistry-sl

    Which are the correct labels for the enthalpies shown in the Hess cycle? 

     

    1

    2

    3

    A

    ΔHӨsol

    ΔHӨhyd

    ΔHӨhyd

    B

    ΔHӨr

    ΔHӨhyd

    ΔHӨhyd

    C

    ΔHӨhyd

    ΔHӨsol

    ΔHӨhyd

    D

    ΔHӨr

    ΔHӨsol

    ΔHӨsol

      Choose your answer
        

      Question 10

      Marks: 1

      The hydration enthalpy of anhydrous copper(II) sulfate, labelled as ΔHexp, cannot be measured directly. It can be found indirectly by determining the solution enthalpies of anhydrous and hydrated copper(II) sulfate.

      q10_5-2_mcq_medium_ib-chemistry-sl

      Which of the following statements correctly explains why the value for ΔHexp for this reaction cannot be measured directly?

      • Measuring the temperature change in a solid is difficult

      • The reaction is very slow

      • The reaction has high energy requirements

      • The reaction is endothermic

      Choose your answer