Enthalpy change Part 1

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

• 2NO(g) → N₂(g) + O₂(g)

• 2CO(g) + O₂(g) → 2CO₂(g)

• H₂O(l) + NaCl(s) → NaCl(aq)

• K(s) + Mn(s) + 2O₂(g) → KMnO₄(s)

Which reaction has an enthalpy change equal to the standard enthalpy change of formation of propane?

• 3C(g) + 4H₂(g) → C₃H₈(g)

• 3C(g) + 8H(g) → C₃H₈(g)

• 3C(s) + 4H₂(g) → C₃H₈(g)

• 3C(s) + 4H₂(g) → C₃H₈(l)

The equation for a reaction is shown.

H₂(g) + ½ O₂(g) → H₂O(l) ;

ΔH = x kJ mol^–1

Which pair of descriptions is fully correct for this reaction?

• A

• B

• C

• D

For which reactions does the value of ΔH^o represent both a standard enthalpy change of combustion and a standard enthalpy change of formation?

• C(s) + O₂(g) → CO₂(g)

• 2C(s) + O₂(g) → 2CO(g)

• CO(g) + ½ O₂(g) → CO₂(g)

The reaction pathway for a reversible reaction is shown

Which statements are correct?

• The enthalpy change for the backward reaction is +90 kJ mol^–1.

• The forward reaction is exothermic.

• The enthalpy change for the forward reaction is –30 kJ mol^–1

The reaction pathway for a reversible reaction is shown.

Which statements are correct?

• The enthalpy change for the backward reaction is –20 kJ mol^–1.

• The forward reaction is endothermic.

• The activation energy for the forward reaction is +70 kJ mol^–1.

Enthalpy changes, ΔH, can be positive or negative.

Which row is correct?

• A

• B

• C

• D

A reaction pathway diagram is shown.

Which enthalpy change could the diagram not apply to?

• enthalpy of atomisation

• enthalpy of combustion

• enthalpy of formation

• enthalpy of neutralisation

Which equation represents the standard enthalpy change of formation of ethanol, C₂H₅OH?

• 2C(g) + 3H₂(g) + ½ O₂(g) → C₂H₅OH(l)

• 2C(s) + 3H₂(g) + ½ O₂(g) → C₂H₅OH(l)

• 2C(s) + 3H₂(g) + ½ O₂(g) → C₂H₅OH(g)

• 2C(g) + 6H(g) + O(g) → C₂H₅OH(l)

The diagram represents the reaction pathway for the following reaction.

W(g) + X(g) → Y(g) + Z(g)

What statement can be made about the reverse reaction,

Y(g) + Z(g) → W(g) + X(g)?

• It will have a larger activation energy and a positive ΔH.

• It will have a larger activation energy and a negative ΔH.

• It will have a smaller activation energy and a positive ΔH.

• It will have a smaller activation energy and a negative ΔH.