IB Chemistry Energetics SL

When 100 cm³ of 1.0 mol dm^–3 HCl is mixed with 100 cm3 of 1.0 mol dm^–3 NaOH, the temperature of the resulting solution increases by 5.0 °C. What will be the temperature change, in °C, when 50 cm³ of these two solutions are mixed?

• 2.5

• 5.0

• 10

• 20

Which statement about bonding is correct?

• Bond breaking is endothermic and requires energy.

• Bond breaking is endothermic and releases energy.

• Bond making is exothermic and requires energy

• Bond making is endothermic and releases energy.

Consider the following reactions.

Cu₂O(s) + O₂(g) → 2CuO(s) ∆H^O = –144 kJ

Cu₂O(s) → Cu(s) + CuO(s) ∆H^O = +11 kJ

What is the value of ∆H^O, in kJ, for this reaction?

Cu(s) + O₂(g) → CuO(s)

• –144 + 11

• +144 – 11

• –144 – 11

• +144 + 11

Consider the two reactions involving iron and oxygen.

2Fe(s) + O₂(g) → 2FeO(s) ∆H^O = –544 kJ

4Fe(s) + 3O₂(g) → 2Fe₂O₃(s) ∆H^O = –1648 kJ

What is the enthalpy change, in kJ, for the reaction below?

4FeO(s) + O2(g) → 2Fe₂O3(s)

• –1648 – 2(–544)

• –544 – (–1648)

• –1648 – 544

• –1648 – 2(544)

Which processes have a negative enthalpy change?

I. 2CH₃OH(l) + 3O₂(g) → 2CO₂(g) + 4H₂O(l)

II. HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

III. H₂O(g) → H₂O(l)

• I and II only

• I and III only

• II and III only

• I, II and III

Which equation represents the bond enthalpy for the H–Br bond in hydrogen bromide?

• HBr(g) → H(g) + Br(g)

• HBr(g) → H(g) + Br(l)

• HBr(g) → H(g) + Br₂(1)

• HBr(g) → H(g) + 1/2Br₂(g)

Which types of reaction are always exothermic?

I. Neutralization

II. Decomposition

III. Combustion

• I and II only

• I and III only

• II and III only

• I, II and III

A pure aluminium block with a mass of 10 g is heated so that its temperature increases from 20 °C to 50 °C . The specific heat capacity of aluminium is 8.99 × 10^–1 J g^–1 K^–1. Which expression gives the heat energy change in kJ?

• 10 × 8.99 × 10^–1 × 303

• 10 × 8.99 × 10^–1 × 30

• (10 × 8.99 × 10^–1 × 303)/1000

• (10 × 8.99 × 10^–1 × 30)/1000

Which statement is correct given the enthalpy level diagram below?

• The reaction is endothermic and the products are more thermodynamically stable than the reactants.

• The reaction is exothermic and the products are more thermodynamically stable than the reactants.

• The reaction is endothermic and the reactants are more thermodynamically stable than the products.

• The reaction is exothermic and the reactants are more thermodynamically stable than the products.

Identical pieces of magnesium are added to two beakers, A and B, containing hydrochloric acid.

Both acids have the same initial temperature but their volumes and concentrations differ.

Which statement is correct?

• he maximum temperature in A will be higher than in B.

• The maximum temperature in A and B will be equal.

• It is not possible to predict whether A or B will have the higher maximum temperature.

• The temperature in A and B will increase at the same rate.