5.2 Hess’s Law

What is the enthalpy change of the reaction, in kJ?

2C (graphite) + O₂(g) → 2CO (g)

A.  −394 − 283

B.  2(−394) + 2(−283)

C.  −394 + 283

D.  2(−394) + 2(283)

What is the enthalpy change of the reaction, in kJ?

2C (graphite) + O₂(g) → 2CO (g)

A.  −394 − 283

B.  2(−394) + 2(−283)

C.  −394 + 283

D.  2(−394) + 2(283)

Thermodynamic data for the decomposition of calcium carbonate is given.

Calculate the enthalpy change of reaction, ΔH, in kJ, for the decomposition of calcium carbonate.

Thermodynamic data for the decomposition of calcium carbonate is given.

Calculate the enthalpy change of reaction, ΔH, in kJ, for the decomposition of calcium carbonate.

Thermodynamic data for the decomposition of calcium carbonate is given.

Calculate the enthalpy change of reaction, ΔH, in kJ, for the decomposition of calcium carbonate.

What is the enthalpy of combustion of butane in kJ mol⁻¹?

2C₄H₁₀(g) + 13O₂(g) → 8CO₂(g) + 10H₂O(l)

A.     4x + 5y − z 

B.     4x + 5y + z 

C.     8x + 10y − 2z 

D.     8x + 5y + 2z

What is the enthalpy of combustion of butane in kJ mol⁻¹?

2C₄H₁₀(g) + 13O₂(g) → 8CO₂(g) + 10H₂O(l)

A.     4x + 5y − z 

B.     4x + 5y + z 

C.     8x + 10y − 2z 

D.     8x + 5y + 2z

Determine the standard enthalpy change, ΔH^Θ, for the following similar reaction, using ΔH_f values in section 12 of the data booklet.

3C₂H₂(g) → C₆H₆(l)

Determine the standard enthalpy change, ΔH^Θ, for the following similar reaction, using ΔH_f values in section 12 of the data booklet.

3C₂H₂(g) → C₆H₆(l)

Determine the standard enthalpy change, ΔH^Θ, for the following similar reaction, using ΔH_f values in section 12 of the data booklet.

3C₂H₂(g) → C₆H₆(l)

Outline why no value is listed for H₂(g).

Outline why no value is listed for H₂(g).

Outline why no value is listed for H₂(g).

Determine the value of ΔH^Θ, in kJ, for the reaction using the values in the table.

Determine the value of ΔH^Θ, in kJ, for the reaction using the values in the table.

Determine the value of ΔH^Θ, in kJ, for the reaction using the values in the table.

Determine the value of ΔH^Θ, in kJ, for the reaction using the values in the table.

Determine the value of ΔH^Θ, in kJ, for the reaction using the values in the table.

Determine the value of ΔH^Θ, in kJ, for the reaction using the values in the table.

Which equation represents the standard enthalpy of formation of lithium oxide?

A.  4Li (s) + O₂(g) → 2Li₂O (s)

B.  2Li (s) + $\frac{1}{2}$O₂(g) → Li₂O (s)

C.  Li (s) + $\frac{1}{4}$O₂(g) → $\frac{1}{2}$Li₂O (s)

D.  Li (g) + $\frac{1}{4}$O₂(g) → $\frac{1}{2}$Li₂O (g)

Which equation represents the standard enthalpy of formation of lithium oxide?

A.  4Li (s) + O₂(g) → 2Li₂O (s)

B.  2Li (s) + $\frac{1}{2}$O₂(g) → Li₂O (s)

C.  Li (s) + $\frac{1}{4}$O₂(g) → $\frac{1}{2}$Li₂O (s)

D.  Li (g) + $\frac{1}{4}$O₂(g) → $\frac{1}{2}$Li₂O (g)

Calculate the standard enthalpy change (ΔH^⦵) for the forward reaction in kJ mol⁻¹.

ΔH^⦵_f PCl₃(g) = −306.4 kJ mol⁻¹

ΔH^⦵_f PCl₅(g) = −398.9 kJ mol⁻¹

Calculate the standard enthalpy change (ΔH^⦵) for the forward reaction in kJ mol⁻¹.

ΔH^⦵_f PCl₃(g) = −306.4 kJ mol⁻¹

ΔH^⦵_f PCl₅(g) = −398.9 kJ mol⁻¹

Calculate the standard enthalpy change (ΔH^⦵) for the forward reaction in kJ mol⁻¹.

ΔH^⦵_f PCl₃(g) = −306.4 kJ mol⁻¹

ΔH^⦵_f PCl₅(g) = −398.9 kJ mol⁻¹

Calculate the standard enthalpy change (ΔH^⦵) for the forward reaction in kJ mol⁻¹.

ΔH^⦵_f PCl₃(g) = −306.4 kJ mol⁻¹

ΔH^⦵_f PCl₅(g) = −398.9 kJ mol⁻¹

Calculate the standard enthalpy change (ΔH^⦵) for the forward reaction in kJ mol⁻¹.

ΔH^⦵_f PCl₃(g) = −306.4 kJ mol⁻¹

ΔH^⦵_f PCl₅(g) = −398.9 kJ mol⁻¹

Calculate the standard enthalpy change (ΔH^⦵) for the forward reaction in kJ mol⁻¹.

ΔH^⦵_f PCl₃(g) = −306.4 kJ mol⁻¹

ΔH^⦵_f PCl₅(g) = −398.9 kJ mol⁻¹

Determine the standard enthalpy change, ΔH^Θ, of step 1.

Determine the standard enthalpy change, ΔH^Θ, of step 1.

Determine the standard enthalpy change, ΔH^Θ, of step 1.

Copper(II) chloride is used as a catalyst in the production of chlorine from hydrogen chloride.

4HCl (g) + O₂ (g) → 2Cl₂ (g) + 2H₂O (g)

Calculate the standard enthalpy change, ΔH^θ, in kJ, for this reaction, using section 12 of the data booklet.

Copper(II) chloride is used as a catalyst in the production of chlorine from hydrogen chloride.

4HCl (g) + O₂ (g) → 2Cl₂ (g) + 2H₂O (g)

Calculate the standard enthalpy change, ΔH^θ, in kJ, for this reaction, using section 12 of the data booklet.

Copper(II) chloride is used as a catalyst in the production of chlorine from hydrogen chloride.

4HCl (g) + O₂ (g) → 2Cl₂ (g) + 2H₂O (g)

Calculate the standard enthalpy change, ΔH^θ, in kJ, for this reaction, using section 12 of the data booklet.

What is the value for enthalpy of formation of methane from the given enthalpies of combustion?

C (s) + O₂ (g) → CO₂ (g)                               ΔH = −394 kJ mol⁻¹

H₂ (g) + $\frac{1}{2}$O₂ (g) → H₂O (l)                            ΔH = −286 kJ mol⁻¹

CH₄ (g) + 2O₂ (g) → CO₂ (g) + 2H₂O (l)         ΔH = −891 kJ mol⁻¹

A.   (−394 − 286 − 891) kJ mol⁻¹

B.   (−394 − (2 × 286) − 891) kJ mol⁻¹

C.   (−394 − 286 + 891) kJ mol⁻¹

D.   (−394 − (2 × 286) + 891) kJ mol⁻¹

What is the value for enthalpy of formation of methane from the given enthalpies of combustion?

C (s) + O₂ (g) → CO₂ (g)                               ΔH = −394 kJ mol⁻¹

H₂ (g) + $\frac{1}{2}$O₂ (g) → H₂O (l)                            ΔH = −286 kJ mol⁻¹

CH₄ (g) + 2O₂ (g) → CO₂ (g) + 2H₂O (l)         ΔH = −891 kJ mol⁻¹

A.   (−394 − 286 − 891) kJ mol⁻¹

B.   (−394 − (2 × 286) − 891) kJ mol⁻¹

C.   (−394 − 286 + 891) kJ mol⁻¹

D.   (−394 − (2 × 286) + 891) kJ mol⁻¹

Calculate the standard enthalpy change, $\text{Δ}{H}^{⦵}$, of the reaction. Use section 12 of the data booklet.

$\text{Δ}{H}_f^{⦵}$ ammonium nitrate = −366 kJ mol⁻¹

$\text{Δ}{H}_f^{⦵}$ dinitrogen monoxide = 82 kJ mol⁻¹

Calculate the standard enthalpy change, $\text{Δ}{H}^{⦵}$, of the reaction. Use section 12 of the data booklet.

$\text{Δ}{H}_f^{⦵}$ ammonium nitrate = −366 kJ mol⁻¹

$\text{Δ}{H}_f^{⦵}$ dinitrogen monoxide = 82 kJ mol⁻¹

Calculate the standard enthalpy change, $\text{Δ}{H}^{⦵}$, of the reaction. Use section 12 of the data booklet.

$\text{Δ}{H}_f^{⦵}$ ammonium nitrate = −366 kJ mol⁻¹

$\text{Δ}{H}_f^{⦵}$ dinitrogen monoxide = 82 kJ mol⁻¹

The enthalpy changes for two reactions are given.

Br₂ (l) + F₂ (g) → 2BrF (g)         ΔH = x kJ
Br₂ (l) + 3F₂ (g) → 2BrF₃ (g)      ΔH = y kJ

What is the enthalpy change for the following reaction?

BrF (g) + F₂ (g) → BrF₃ (g)

A.  x – y

B.  –x + y

C.  $\frac{1}{2}$(–x + y)

D.  $\frac{1}{2}$(x – y)

The enthalpy changes for two reactions are given.

Br₂ (l) + F₂ (g) → 2BrF (g)         ΔH = x kJ
Br₂ (l) + 3F₂ (g) → 2BrF₃ (g)      ΔH = y kJ

What is the enthalpy change for the following reaction?

BrF (g) + F₂ (g) → BrF₃ (g)

A.  x – y

B.  –x + y

C.  $\frac{1}{2}$(–x + y)

D.  $\frac{1}{2}$(x – y)

Calculate the standard enthalpy change for this reaction using the following data.

Calculate the standard enthalpy change for this reaction using the following data.

Calculate the standard enthalpy change for this reaction using the following data.

Determine the standard enthalpy change, ΔH^Θ, for the following similar reaction, using ΔH_f values in section 12 of the data booklet.

3C₂H₂(g) → C₆H₆(l)

Determine the standard enthalpy change, ΔH^Θ, for the following similar reaction, using ΔH_f values in section 12 of the data booklet.

3C₂H₂(g) → C₆H₆(l)

Determine the standard enthalpy change, ΔH^Θ, for the following similar reaction, using ΔH_f values in section 12 of the data booklet.

3C₂H₂(g) → C₆H₆(l)

Outline why no value is listed for H₂(g).

Outline why no value is listed for H₂(g).

Outline why no value is listed for H₂(g).

What is the enthalpy change of combustion of urea, (NH₂)₂CO, in kJ mol⁻¹?

2(NH₂)₂CO(s) + 3O₂(g) → 2CO₂(g) + 2N₂(g) + 4H₂O(l)

A.     2 × (−333) −2 × (−394) −4 × (−286)

B.     $\frac{1}{2}$[2 × (−394) + 4 × (−286) −2 × (−333)]

C.     2 × (−394) + 4 × (−286) −2 × (−333)

D.     $\frac{1}{2}$[2 × (−333) −2 × (−394) −4 × (−286)]

What is the enthalpy change of combustion of urea, (NH₂)₂CO, in kJ mol⁻¹?

2(NH₂)₂CO(s) + 3O₂(g) → 2CO₂(g) + 2N₂(g) + 4H₂O(l)

A.     2 × (−333) −2 × (−394) −4 × (−286)

B.     $\frac{1}{2}$[2 × (−394) + 4 × (−286) −2 × (−333)]

C.     2 × (−394) + 4 × (−286) −2 × (−333)

D.     $\frac{1}{2}$[2 × (−333) −2 × (−394) −4 × (−286)]

Consider the following reactions:

Fe₂O₃ (s) + CO (g) → 2FeO (s) + CO₂ (g)       ΔH^Θ = −3 kJ

Fe (s) + CO₂ (g) → FeO (s) + CO (g)               ΔH^Θ = +11 kJ

What is the ΔH^Θ value, in kJ, for the following reaction?

Fe₂O₃ (s) + 3CO (g) → 2Fe (s) + 3CO₂ (g)

A.   −25

B.   −14

C.   +8

D.   +19

Consider the following reactions:

Fe₂O₃ (s) + CO (g) → 2FeO (s) + CO₂ (g)       ΔH^Θ = −3 kJ

Fe (s) + CO₂ (g) → FeO (s) + CO (g)               ΔH^Θ = +11 kJ

What is the ΔH^Θ value, in kJ, for the following reaction?

Fe₂O₃ (s) + 3CO (g) → 2Fe (s) + 3CO₂ (g)

A.   −25

B.   −14

C.   +8

D.   +19

Determine the enthalpy change, ΔH, in kJ, for this reaction using data from the table and section 12 of the data booklet.

Determine the enthalpy change, ΔH, in kJ, for this reaction using data from the table and section 12 of the data booklet.

Determine the enthalpy change, ΔH, in kJ, for this reaction using data from the table and section 12 of the data booklet.

What is the enthalpy change of reaction for the following equation?

C₂H₄ (g) + H₂ (g) → C₂H₆ (g)

C₂H₄ (g) + 3O₂ (g) → 2CO₂ (g) + 2H₂O (l)        ΔH = x

C₂H₆ (g) + $\frac{7}{2}$O₂ (g) → 2CO₂ (g) + 3H₂O (l)    ΔH = y

H₂ (g) + $\frac{1}{2}$O₂ (g) → H₂O (l)                           ΔH = z

A. x + y + z

B. −x − y + z

C. x − y − z

D. x − y + z

What is the enthalpy change of reaction for the following equation?

C₂H₄ (g) + H₂ (g) → C₂H₆ (g)

C₂H₄ (g) + 3O₂ (g) → 2CO₂ (g) + 2H₂O (l)        ΔH = x

C₂H₆ (g) + $\frac{7}{2}$O₂ (g) → 2CO₂ (g) + 3H₂O (l)    ΔH = y

H₂ (g) + $\frac{1}{2}$O₂ (g) → H₂O (l)                           ΔH = z

A. x + y + z

B. −x − y + z

C. x − y − z

D. x − y + z

Determine the enthalpy change, ΔH, in kJ, for this reaction using data from the table and section 12 of the data booklet.

Determine the enthalpy change, ΔH, in kJ, for this reaction using data from the table and section 12 of the data booklet.

Determine the enthalpy change, ΔH, in kJ, for this reaction using data from the table and section 12 of the data booklet.

Consider the following equations.

2Al (s) + $\frac{3}{2}$O₂ (g) → Al₂O₃ (s)    ΔH^Ɵ = −1670 kJ
Mn (s) + O₂ (g) → MnO₂ (s)    ΔH^Ɵ = −520 kJ

What is the standard enthalpy change, in kJ, of the reaction below?

4Al (s) + 3MnO₂ (s) → 2Al₂O₃ (s) + 3Mn (s)

A. −1670 + 520

B. $\frac{3}{2}$(−1670) + 3(520)

C. 2(−1670) + 3(−520)

D. 2(−1670) + 3(520)

Consider the following equations.

2Al (s) + $\frac{3}{2}$O₂ (g) → Al₂O₃ (s)    ΔH^Ɵ = −1670 kJ
Mn (s) + O₂ (g) → MnO₂ (s)    ΔH^Ɵ = −520 kJ

What is the standard enthalpy change, in kJ, of the reaction below?

4Al (s) + 3MnO₂ (s) → 2Al₂O₃ (s) + 3Mn (s)

A. −1670 + 520

B. $\frac{3}{2}$(−1670) + 3(520)

C. 2(−1670) + 3(−520)

D. 2(−1670) + 3(520)

Copper(II) chloride is used as a catalyst in the production of chlorine from hydrogen chloride.

4HCl (g) + O₂ (g) → 2Cl₂ (g) + 2H₂O (g)

Calculate the standard enthalpy change, ΔH^θ, in kJ, for this reaction, using section 12 of the data booklet.

Copper(II) chloride is used as a catalyst in the production of chlorine from hydrogen chloride.

4HCl (g) + O₂ (g) → 2Cl₂ (g) + 2H₂O (g)

Calculate the standard enthalpy change, ΔH^θ, in kJ, for this reaction, using section 12 of the data booklet.

Copper(II) chloride is used as a catalyst in the production of chlorine from hydrogen chloride.

4HCl (g) + O₂ (g) → 2Cl₂ (g) + 2H₂O (g)

Calculate the standard enthalpy change, ΔH^θ, in kJ, for this reaction, using section 12 of the data booklet.

What is the enthalpy change of the reaction?

C₆H₁₄ (l) → C₂H₄ (g) + C₄H₁₀ (g)

A.  + 1411 + 2878 + 4163

B.  + 1411 − 2878 − 4163

C.  + 1411 + 2878 − 4163

D.  − 1411 − 2878 + 4163

What is the enthalpy change of the reaction?

C₆H₁₄ (l) → C₂H₄ (g) + C₄H₁₀ (g)

A.  + 1411 + 2878 + 4163

B.  + 1411 − 2878 − 4163

C.  + 1411 + 2878 − 4163

D.  − 1411 − 2878 + 4163

Which equation shows the enthalpy of formation, $∆H_{\mathrm{f}}$, of ethanol?

A.  $2\mathrm{C} \left(\mathrm{s}\right)+3{\mathrm{H}}_2 \left(\mathrm{g}\right)+\frac{1}{2}{\mathrm{O}}_2 \left(\mathrm{g}\right)\to {\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH} \left(\mathrm{g}\right)$

B.  $4\mathrm{C} \left(\mathrm{s}\right)+6{\mathrm{H}}_2 \left(\mathrm{g}\right)+{\mathrm{O}}_2 \left(\mathrm{g}\right)\to 2{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH} \left(\mathrm{g}\right)$

C.  $2\mathrm{C} \left(\mathrm{s}\right)+3{\mathrm{H}}_2 \left(\mathrm{g}\right)+\frac{1}{2}{\mathrm{O}}_2 \left(\mathrm{g}\right)\to {\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH} \left(\mathrm{l}\right)$

D.  $4\mathrm{C} \left(\mathrm{s}\right)+6{\mathrm{H}}_2 \left(\mathrm{g}\right)+{\mathrm{O}}_2 \left(\mathrm{g}\right)\to 2{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH} \left(\mathrm{l}\right)$

Which equation shows the enthalpy of formation, $∆H_{\mathrm{f}}$, of ethanol?

A.  $2\mathrm{C} \left(\mathrm{s}\right)+3{\mathrm{H}}_2 \left(\mathrm{g}\right)+\frac{1}{2}{\mathrm{O}}_2 \left(\mathrm{g}\right)\to {\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH} \left(\mathrm{g}\right)$

B.  $4\mathrm{C} \left(\mathrm{s}\right)+6{\mathrm{H}}_2 \left(\mathrm{g}\right)+{\mathrm{O}}_2 \left(\mathrm{g}\right)\to 2{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH} \left(\mathrm{g}\right)$

C.  $2\mathrm{C} \left(\mathrm{s}\right)+3{\mathrm{H}}_2 \left(\mathrm{g}\right)+\frac{1}{2}{\mathrm{O}}_2 \left(\mathrm{g}\right)\to {\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH} \left(\mathrm{l}\right)$

D.  $4\mathrm{C} \left(\mathrm{s}\right)+6{\mathrm{H}}_2 \left(\mathrm{g}\right)+{\mathrm{O}}_2 \left(\mathrm{g}\right)\to 2{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH} \left(\mathrm{l}\right)$

Which combination will give you the enthalpy change for the hydrogenation of ethene to ethane, $∆H_3$?

A.  $-∆H_2+∆H_1-∆H_4$

B.  $∆H_2\mathit{-}∆H_1+∆H_4$

C.  $∆H_2+∆H_1-∆H_4$

D.  $-∆H_2\mathit{-}∆H_1+∆H_4$

Which combination will give you the enthalpy change for the hydrogenation of ethene to ethane, $∆H_3$?

A.  $-∆H_2+∆H_1-∆H_4$

B.  $∆H_2\mathit{-}∆H_1+∆H_4$

C.  $∆H_2+∆H_1-∆H_4$

D.  $-∆H_2\mathit{-}∆H_1+∆H_4$

Calculate the enthalpy change of reaction, ΔH, in kJ, for the decomposition of calcium carbonate.

Calculate the enthalpy change of reaction, ΔH, in kJ, for the decomposition of calcium carbonate.

Calculate the enthalpy change of reaction, ΔH, in kJ, for the decomposition of calcium carbonate.

Calculate the enthalpy change, ΔH^⦵, for the Haber–Bosch process, in kJ, using the following data.

$∆H_{ \mathrm{f}}^{⦵}\left({\mathrm{NH}}_3\right)=-46.2 \mathrm{kJ} {\mathrm{mol}}^{-1}$.

Calculate the enthalpy change, ΔH^⦵, for the Haber–Bosch process, in kJ, using the following data.

$∆H_{ \mathrm{f}}^{⦵}\left({\mathrm{NH}}_3\right)=-46.2 \mathrm{kJ} {\mathrm{mol}}^{-1}$.

Calculate the enthalpy change, ΔH^⦵, for the Haber–Bosch process, in kJ, using the following data.

$∆H_{ \mathrm{f}}^{⦵}\left({\mathrm{NH}}_3\right)=-46.2 \mathrm{kJ} {\mathrm{mol}}^{-1}$.

Calculate the standard enthalpy change, $\text{Δ}{H}^{⦵}$, of the reaction. Use section 12 of the data booklet.

$\text{Δ}{H}_f^{⦵}$ ammonium nitrate = −366 kJ mol⁻¹

$\text{Δ}{H}_f^{⦵}$ dinitrogen monoxide = 82 kJ mol⁻¹

Calculate the standard enthalpy change, $\text{Δ}{H}^{⦵}$, of the reaction. Use section 12 of the data booklet.

$\text{Δ}{H}_f^{⦵}$ ammonium nitrate = −366 kJ mol⁻¹

$\text{Δ}{H}_f^{⦵}$ dinitrogen monoxide = 82 kJ mol⁻¹

Calculate the standard enthalpy change, $\text{Δ}{H}^{⦵}$, of the reaction. Use section 12 of the data booklet.

$\text{Δ}{H}_f^{⦵}$ ammonium nitrate = −366 kJ mol⁻¹

$\text{Δ}{H}_f^{⦵}$ dinitrogen monoxide = 82 kJ mol⁻¹