AS energetics 1

For which equation is the enthalpy change correctly described as an enthalpy change of formation?

Which equation has an. enthalpy change of reaction which corresponds to the standard enthalpy change of atomization of chlorine?

The equation for a reaction is shown.

H₂(g) + 1/2 O₂(g) → H₂O (l) ; ΔH = x kJ mol ^-1

• It represents enthalpy change of formation only.

• It represents enthalpy change of formation and combustion.

• x is positive

• x is negative

Hydrogen peroxide slowly decomposes into water and oxygen. The enthalpy change of reaction can be calculated using standard enthalpies of formation.

ΔH^ϴf(hydrogen peroxide(I)) = - 187.8 kJ/mol

ΔH^ϴf(water(I)) = - 285.8 kJ/mol

Using a Hess cycle, what is the enthalpy change of reaction for this decomposition?

2H₂O₂(l) → 2H₂O(l) + O₂ (g)

• + 98 kJ/mol

• - 98 kJ/mol

• - 196 kJ/mol

• - 947.2 kJ/mol

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 - 940 kJ/mol and - 110 kJ/mol respectively.

What is the standard enthalpy change of this reaction.

• - 830 kJ/mol

• - 720 kJ/mol

• + 720 kJ/mol

• + 830 kJ/mol

Skiers trapped by snowstorms use heat packs to keep warm. The heat may be generated by the reaction below.

4Fe(s) + 3O₂(g) → 2Fe₂O₃(s); ΔH^Θ = -1648 kJ/mol

What is the standard enthalpy change of formation of iron(III) oxide?

• 0 kJ/mol

• -824 kJ/mol

• -1648 kJ/mol

• -3296 kJ/mol

What is the standard enthalpy change of combustion of propane-1-ol, in kJ/mol.

• - 394 -286 - 303

• 303 - (4 x 286) - (3 x 394)

• 394 + 286 - 303

• (3 x 394) + (4 x 286) +303

50 cm³ of 2.50 mol dm^-3 hydrochloric acid was placed in a polystyrene beaker of negligible heat capacity. Its temperature was recorded and then 50 cm³ of 2.50 mol dm^-3 NaOH at the same temperature was quickly added, with stirring. The temperature rose by 17 ºC.

The resulting solution may be considered to have specific heat capacity of 4.2 Jg^-1K^-1.

What is an approximately value for the molar enthalpy change of neutralization of hydrochloric acid and sodium hydroxide from this experiment?

What are P, Q and R?

• P: ethanoic acid

• P: sulfuric acid

• Q: ammonia

• Q: sodium hydroxide

• R: potassium hydroxide

In a calorimetric experiment 1.60 g of a fuel are burnt. 45.0% of the energy released is absorbed by 200 g of water. The temperature of the water rises from 18.0 °C to 66.0 °C.

What is the total energy released per gram of fuel burnt?

• 25100 J

• 55700 J

• 89200 J

• 143000 J