IB Chemistry Energetics SL Topic 5

ΔH value in an endothermic reaction is a positive number.

• True
• False

Match the definition below to the correct term.

The enthalpy change that takes place when one mole of a compound is formed from its elements in their standard states under standard conditions.

• The enthalpy of neutralisation

• The enthalpy of combustion

• The enthalpy of formation

• The enthalpy of reaction

Define standard enthalpy of combustion.

• Heat released when one mole of substance is burnt completely in excess oxygen.

• Heat absorbed when one mole of substance is burnt completely in excess oxygen under standard state.

• Heat released when one mole of substance is burnt completely in excess oxygen under standard state.

• Heat change when one mole of substance is burnt partially in excess oxygen under standard state.

Which of the following has a ΔH_f^o value of 0?

• Br₂(g)

• N(g)

• CO(g)

• N₂(g)

Which of the equation below refers to the standard enthalpy of formation, ΔH_f^o?

• Na(g) ---> Na⁺(g) + e^- ΔH = -364 kJmol^-1

• C₂H₅OH(l) + 3O₂(g) ---> 2CO₂(g) + 3H₂O (l) ΔH = - 1286 kJmol^-1

• 2C(s) + 2H₂(g) ---> C₂H₄ (g) ΔH = - 52.3 kJmol^-1

• Na⁺(g) ---> Na⁺(aq) ΔH = - 364 kJmol^-1

What letter represents the activation energy?

• A
• B
• C
• D

Using the equations below:

C_(s) + O_2(g) → CO_2(g) ∆H = –390 kJ

Mn_(s) + O_2(g) → MnO_2(s) ∆H = –520 kJ

what is ∆H (in kJ) for the following reaction?

MnO_2(s) + C_(s) → Mn_(s) + CO_2(g)

• 910

• 130

• -130

• -910

Using the equations below

Cu_(s) + ¹/₂O_2(g) → CuO_(s) ∆H = –156 kJ

2Cu_(s) + O_2(g) → Cu₂O_(s) ∆H = –170 kJ

what is the value of ∆H (in kJ) for the following reaction?

2CuO_(s) → Cu₂O_(s) + ¹/₂O_2(g)

• 142

• 15

• -15

• -142

The following equations show the oxidation of carbon and carbon monoxide to carbon dioxide.

C_(s) +O_2(g) → CO_2(g) ΔH = –x kJ mol^–1

CO_(g) + O_2(g) → CO_2(g) ΔH = –y kJ mol^–1

What is the enthalpy change, in kJ mol^–1, for the oxidation of carbon to carbon monoxide?

C_(s) + O_2(g) → CO_(g)

• x + y

• -x - y

• y - x

• x - y

How much heat is needed to raise the temperature of 50 g of iron by 15°C? (specific heat of iron = 0.444 J/g°C)

• 333 J

• 33.3 J

• 33300 J

• 3330 J