Endothermic and exothermic reactions

Chemia IBPaper 1A, maj 2026, TZ3wzorowane1 pktzamknięteśrednie (szac.)

Zadanie 15

The diagram shows the energy profile of a reaction. Which expression could give the enthalpy change, ΔH, of this reaction in kJ mol⁻¹? A. +87 − 215 B. −215 + 87 C. +215 − 87 D. −215 − 87

• Materiał graficzny

Chemia IBPaper 1A, maj 2026, TZ2wzorowane1 pktzamknięteśrednie (szac.)

Zadanie 16

Which of the following processes are exothermic? I. K(g) → K⁺(g) + e⁻ II. H₂O(g) → H₂O(l) III. Ag⁺(g) + Cl⁻(g) → AgCl(s) A. I and II only B. I and III only C. II and III only D. I, II and III

Chemia IBPaper 1B, maj 2025, TZ3wzorowane4 pktotwarteśrednie (szac.)

Zadanie 1b

The sealed vessel was left for the reaction to proceed. Suggest two properties of the system, other than its colour, that could be measured to follow the progress of the reaction over time, and predict how each would change as the forward reaction proceeds.

Chemia IBPaper 2, maj 2025, TZ2wzorowane7 pktobliczenioweśrednie (szac.)

Zadanie 3a

Suppose carbonyl dibromide were made by a free-radical chain reaction of carbon monoxide, CO, with bromine vapour, Br₂, started by ultraviolet light. The questions below treat this hypothetical route with the bond-enthalpy model. (i) Write an…

• Materiał graficzny

Chemia IBPaper 1A, maj 2025, TZ2wzorowane1 pktzamkniętełatwe (szac.)

Zadanie 15

The energy profile below was recorded for a reaction. Which pair of statements is consistent with it? In each option the first statement compares the enthalpy of the products with that of the reactants and the second gives the sign of ΔH. A. products…

• Materiał graficzny

Chemia IBPaper 1A, maj 2025, TZ3wzorowane1 pktzamkniętełatwe (szac.)

Zadanie 16

Which row correctly describes an endothermic reaction? A. The temperature of the surroundings rises and the products are more stable than the reactants. B. The temperature of the surroundings falls and the products are more stable than the reactants. C. The…

Chemia IBPaper 1A, maj 2025, TZ1wzorowane1 pktzamknięteśrednie (szac.)

Zadanie 18

A chemical reaction occurs in a mixture that starts at the same temperature as its surroundings. Immediately after the reaction, the mixture is warmer than before. Which row correctly describes the energy changes in the system and in the surroundings as the…

Chemia IBPaper 1A, maj 2025, TZ1wzorowane1 pktzamknięteśrednie (szac.)

Zadanie 19

A student stirred 0.030 mol of solid sodium hydrogencarbonate into 40 cm³ of a 1.0 mol dm⁻³ solution of ethanedioic acid. H₂C₂O₄(aq) + 2 NaHCO₃(s) → Na₂C₂O₄(aq) + 2 CO₂(g) + 2 H₂O(l) The temperature of the solution fell from…

Chemia IBPaper 2, listopad 2025, TZ3wzorowane3 pktotwarteśrednie (szac.)

Zadanie 3b

The forward reaction is endothermic, uses platinum as a catalyst, and takes place at 800 K. Sketch the reaction's energy profile both with and without the catalyst present, labelling the activation energies and ΔH.

• Materiał graficzny

Chemia IBPaper 1A, listopad 2025, TZ1wzorowane1 pktzamkniętełatwe (szac.)

Zadanie 16

The potential energy profile of a reaction is shown. Which reaction has this energy profile? A. Cl₂(g) → 2 Cl(g) B. CaCO₃(s) → CaO(s) + CO₂(g) C. N₂O₄(g) → 2 NO₂(g) D. 2 Mg(s) + O₂(g) → 2 MgO(s)

• Materiał graficzny

Chemia IBPaper 1A, specimen 2025wzorowane1 pktzamkniętełatwe (szac.)

Zadanie 16

The enthalpy change of a reaction is ΔH = +58 kJ mol⁻¹. Which statement about this reaction is correct? A. The reaction is endothermic and the products are less stable than the reactants. B. The reaction is endothermic and the products…

Chemia IBPaper 2, maj 2024, TZ2wzorowane4 pktobliczenioweśrednie (szac.)

Zadanie 4c

Propenal can be made by the dehydration of propane-1,2,3-triol (glycerol): CH₂(OH)CH(OH)CH₂OH(l) → CH₂=CHCHO(g) + 2 H₂O(g) Two related reactions were studied separately. Reaction 1:…

Chemia IBPaper 1, maj 2024, TZ2wzorowane1 pktzamknięteśrednie (szac.)

Zadanie 15

Which statement about the energy changes in a reaction between covalent molecules is correct? A. The enthalpy change of the reaction equals the sum of the bond enthalpies of the bonds broken minus the sum of the bond enthalpies of the bonds formed B. The…

Chemia IBPaper 3, maj 2023, TZ1wzorowane1 pktotwartełatwe (szac.)

Zadanie 1a

Outline why the first ionization energies of all the elements in the table are positive, whereas the first electron affinities of most of them are negative.

Chemia IBPaper 1, maj 2023, TZ2wzorowane1 pktzamkniętełatwe (szac.)

Zadanie 13

The standard enthalpy change for the following reaction is −92 kJ mol⁻¹. How much energy, in kJ, is released in the reaction below it? $\tfrac{1}{2}\ce{H2(g)} + \tfrac{1}{2}\ce{Cl2(g)} \rightarrow \ce{HCl(g)}$ H₂(g) + Cl₂(g) → 2 HCl(g)…

Chemia IBPaper 1, maj 2023, TZ1wzorowane1 pktzamknięteśrednie (szac.)

Zadanie 15

Solid sodium hydroxide, NaOH, is dissolved in water and the temperature of the solution increases. Which diagram shows the enthalpy change for dissolving the solid in water? A. Diagram A B. Diagram B C. Diagram C D. Diagram D

• Materiał graficzny

Chemia IBPaper 1, maj 2023, TZ2wzorowane1 pktzamkniętełatwe (szac.)

Zadanie 15

Hydrogen atoms in the gas phase combine to form a covalent bond: H(g) + H(g) → H₂(g) Which statement describes the energy change? A. Energy is absorbed and ΔH is positive B. Energy is released and ΔH is positive C. Energy is released…

Chemia IBPaper 2, listopad 2023, TZ2wzorowane4 pktotwarteśrednie (szac.)

Zadanie 2e

The conversion of carbon dioxide to methanol is usually carried out over a catalyst containing copper and zinc oxide. (i) Sketch energy profiles for the forward reaction, with and without the catalyst, on the axes shown. Label ΔH and the two activation…

• Materiał graficzny

Chemia IBPaper 1, listopad 2023, TZ1wzorowane1 pktzamknięteśrednie (szac.)

Zadanie 14

Which changes are exothermic? I. CH₄(g) + 2 O₂(g) → CO₂(g) + 2 H₂O(l) II. Cl(g) + e⁻ → Cl⁻(g) III. H₂O(l) → H₂O(g) A. I and II only B. I and III only C. II and III only D. I, II and III

Chemia IBPaper 1, listopad 2023, TZ2wzorowane1 pktzamknięteśrednie (szac.)

Zadanie 14

Which of these changes are exothermic? I. N₂(g) + 3 H₂(g) → 2 NH₃(g) II. I₂(s) → I₂(g) III. H₂O(g) → H₂O(l) A. I and II only B. I and III only C. II and III only D. I, II and III

Chemia IBPaper 1, listopad 2023, TZ2wzorowane1 pktzamknięteśrednie (szac.)

Zadanie 16

Which expression gives the enthalpy change, ΔH, of the forward reaction shown in the enthalpy profile? A. II − I B. I − II C. I − III D. III − II

• Materiał graficzny

Chemia IBPaper 2, maj 2022, TZ2wzorowane2 pktotwartełatwe (szac.)

Zadanie 1d

Describe two observations, other than the formation of gas bubbles, that would show that the reaction of sodium with water is exothermic.

Chemia IBPaper 2, maj 2022, TZ2wzorowane5 pktobliczenioweśrednie (szac.)

Zadanie 4e

Ethane reacts with iodine vapour. C₂H₆(g) + I₂(g) → C₂H₅I(g) + HI(g) (i) Calculate the enthalpy change of the reaction, ΔH, using section 12 of the data booklet. (ii) Draw and label an enthalpy level diagram for this reaction on the axes below.

• Materiał graficzny

Chemia IBPaper 1, maj 2022, TZ2wzorowane1 pktzamkniętełatwe (szac.)

Zadanie 13

Which change is exothermic? A. Cl₂(g) → 2 Cl(g) B. H₂O(l) → H₂O(g) C. CH₄(g) → C(g) + 4 H(g) D. H(g) + Br(g) → HBr(g)

Chemia IBPaper 1, maj 2022, TZ1wzorowane1 pktzamkniętełatwe (szac.)

Zadanie 15

The potential energy profile of a reaction is shown. Which statement correctly describes the reaction? A. Endothermic; the products have a lower potential energy than the reactants B. Endothermic; the products are less stable than the reactants C. Exothermic;…

• Materiał graficzny

Chemia IBPaper 1, maj 2022, TZ2wzorowane1 pktzamknięteśrednie (szac.)

Zadanie 17

A reaction has an activation energy of 50 kJ mol⁻¹ and an enthalpy change of −70 kJ mol⁻¹. Which potential energy diagram represents this reaction? A. Graph A B. Graph B C. Graph C D. Graph D

• Materiał graficzny