AP 6.8 Enthalpy of Formation

3 C₂H₂(g) → C₆H₆(g)

What is the standard enthalphy change ΔH^o, for the reaction represented above?

(ΔH^o_f of C₂H₂(g) is 230 kJ mol^-1;

(ΔH^o_f of C₆H₆(g) is 83 kJ mol^-1;)

• -607 kJ

• -147 kJ

• -19 kJ

• +19 kJ

• +773 kJ

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NGSS.HS-PS1-4

2 NH₃(g) → 3 H₂(g) + N₂(g) ΔH°₂₉₈ = 92 kJ/mol_rxn

According to the information above, what is the standard enthalpy of formation, ΔH°_f , for NH₃(g) at 298 K ?

• -92 kJ/mol

• -46 kJ/mol

• 46 kJ/mol

• 92 kJ/mol

• 184 kJ/mol

Tags

NGSS.HS-PS1-4

Based on the information in the table above, which of the following expressions gives the approximate ΔH° for the reaction represented by the following balanced chemical equation?

Fe2O3(s)+3 CO(g)→2 Fe(s)+3 CO2(g)

• ΔH°rxn=[(0kJ/mol)+(−394kJ/mol)]−[(−826kJ/mol)+(−111kJ/mol)]

• ΔH°rxn=[2(0kJ/mol)+ 3(−394kJ/mol)]−[(−826kJ/mol)+ 3(−111kJ/mol)]

• ΔH°rxn=[(−826kJ/mol)+ 3(−111kJ/mol)]−[2(0kJ/mol)+ 3(−394kJ/mol)]

• ΔH°rxn=[(−826kJ/mol)+(−111kJ/mol)]−[(0kJ/mol)+(−394kJ/mol)]

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

The enthalpy change for the reaction 2Al(s)+Fe2O3(s)→2Fe(s)+Al2O3(s) is −860kJ/mol. Based on the standard enthalpies of formation ΔH°f provided in the table, what is the approximate ΔH°f for Fe2O3(s) ?

• +2540kJ/mol

• −2540kJ/mol

• +820kJ/mol

• −820kJ/mol

Tags

NGSS.HS-PS1-4

C(s)+H2O(g)→CO(g)+H2(g)

ΔH°=+131kJ/molrxn

The reaction between C(s) and H2O(g) is represented by the balanced chemical equation above. Based on the enthalpy change of the reaction (ΔH°) and the standard heats of formation (ΔH°f) given in the table below, what is the approximate ΔH°f for CO(g) ?

• −373kJ/mol

• −111kJ/mol

• +111kJ/mol

• +373kJ/mol

Tags

NGSS.HS-PS1-4

NGSS.HS-PS1-2

4 NH₃(g) + 3 O₂(g) → 2 N₂(g) + 6 H₂O(g)

If the standard molar heats of formation of ammonia, NH₃(g), and gaseous water, H₂O(g), are -46 kJ/mol and -242 kJ/mol, respectively, what is the value of ΔH°₂₉₈ for the reaction represented above?

• -190 kJ/mol_rxn

• -290 kJ/mol_rxn

• -580 kJ/mol_rxn

• -1,270 kJ/mol_rxn

• -1,640 kJ/mol_rxn

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

Calculate the enthalpy of reaction (ΔH).

4CO_{2 (g)} + 6H₂O _(g) → 2C₂H_{6 (g)} + 7O_{2 (g)}

ΔH_f^o [CO_2(g)] = -393.5 kJ

ΔH_f^o [H₂O_(g)] = -241.8 kJ

ΔH_f^o [C₂H_6(g)] = -84.7 kJ

• 550.647 KJ/mol

• 2855.584 KJ/mol

• -550.647 KJ/mol

• -2855.584 KJ/mol

Tags

NGSS.HS-PS1-4

The standard enthalpy changes of formation of carbon dioxide and of methanoic acid are −394 kJ/mol and −409 kJ/mol respectively. Calculate the enthalpy change for the reaction

H_{2 (g)} + CO_{2 (g)} → HCOOH _(l)

• −803 kJ/mol

• −15 kJ/mol

• +803 kJ/mol

• +15 kJ/mol

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

The standard enthalpy of formation of NH₃ (g) at 298K is -46 kJmol^-1. What is the enthalpy change of the following reaction?

2NH₃(g) ---> N₂(g) + 3H₂(g)

• -46 kJmol^-1

• +92 kJmol^-1

• -92 kJmol^-1

• +46 kJmol^-1

Tags

NGSS.HS-PS1-4

The standard enthalpies of formation for ethene (C₂H₄), water (H₂O) and ethanol (C₂H₅OH) are +52, -286 and -277 kJ/mol respectively. Calculate ∆H^o for the reaction Ethene + Water → Ethanol

• +61 kJ

• -43 kJ

• -61 kJ

• -511 kJ

• -615 kJ

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1