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CHE 105/110 Introduction to Chemistry - Exercises and Answers

Formation Reactions

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QUESTION ANSWER

1.

Define formation reaction and give an example.

1.

A formation reaction is a reaction that produces one mole of a substance from its elements. Example: C(s) + O2(g) → CO2(g)

3.

Which of the following reactions is a formation reaction? If it is not a formation reaction, explain why.

  1. H2(g) + S(s) → H2S(g)

  2. 2HBr(g) + Cl2(g) → 2HCl(g) + Br2(ℓ)

3.

  1. formation reaction
  2. It is not the formation of a single substance, so it is not a formation reaction.

5.

Which of the following reactions is a formation reaction? If it is not a formation reaction, explain why.

  1. H2(g) + S(s) + 2O2(g) → H2SO4(ℓ)

  2. C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(ℓ)

5.

  1. formation reaction

  2. It is not the formation of a single substance, so it is not a formation reaction.

7.

Write a proper formation reaction for each substance.

  1. H3PO4(s)

  2. Na2O(s)

  3. C3H7OH(ℓ)

7.

  1. 3/2H2(g) + P(s) + 2O2(g) → H3PO4(s)

  2. 2Na(s) + 1/2O2(g) → Na2O(s)

  3. 3C(s) + 1/2O2(g) + 4H2(g) → C3H7OH(ℓ)

9.

Write a proper formation reaction for each substance.

  1. C12H22O11(s)

  2. Zn(NO3)2(s)

  3. Al(OH)3(s)

 

9.

  1. 12C(s) + 11H2(g) + 11/2O2(g) → C12H22O11(s)

  2. Zn(s) + N2(g) + 3O2(g) → Zn(NO3)2

  3. Al(s) + 3/2O2(g) + 3/2H2(g) → Al(OH)3(s)

11.

Write this reaction in terms of formation reactions.

MgCO3(s) → MgO(s) + CO2(g)

11.

MgCO3(s) → Mg(s) + C(s) + 3/2O2(g)

Mg(s) + 1/2O2(g) → MgO(s)

C(s) + O2(g) → CO2(g)

13.

Write this reaction in terms of formation reactions.

2CuCl(s) → Cu(s) + CuCl2(s)

13.

2 × [CuCl(s) → Cu(s) + 1/2Cl2(g)]

Cu(s) → Cu(s)

Cu(s) + Cl2(g) → CuCl2(s)

15.

Determine the enthalpy change of this reaction. Data can be found in Table 2.2 "Enthalpies of Formation for Various Substances".

CH2O(g) + O2 → CO2(g) + H2O(ℓ)

15.

ΔH = −563.44 kJ

17.

Determine the enthalpy change of this reaction. Data can be found in Table 2.2 "Enthalpies of Formation for Various Substances".

Mg(s) + N2O5(g) → MgO(s) + 2NO2(g)

17.

ΔH = −546.7 kJ

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