Zadanie 1b
The second step converts nitrogen monoxide to nitrogen dioxide. 2 NO(g) + O2(g) ⇌ 2 NO2(g) ΔH⊖ = −114 kJ mol−1 (i) Identify the oxidation state of nitrogen in NO and in NO2. (ii) State the equilibrium constant…
Le Chatelier's principle
Apply Le Chatelier's principle to predict and explain how changing concentration, pressure (or volume) or temperature shifts the position of equilibrium, and how a catalyst shortens the time to reach equilibrium without changing the position or K.
Tę umiejętność sprawdzają 33 zadania wzorowane na arkuszach IB z lat 2022–2026.
Zadania sprawdzające tę umiejętność: 33 Otwórz w wyszukiwarce z filtrami
Zadanie 2a
Iodine crystals, I2(s), were sealed in a flask and left until an equilibrium was reached with violet vapour above the crystals. I2(s) ⇌ I2(g) (i) Name the change of state from I2(s) to I2(g) and state the type of force between…
Zadanie 2b
The oxidation of sulfur dioxide to sulfur trioxide is an equilibrium reaction. 2 SO2(g) + O2(g) ⇌ 2 SO3(g) (i) State the equilibrium constant expression, K, for the reaction. (ii) Explain, with a reason, how compressing the gas mixture at constant…
- Materiał graficzny
Zadanie 27
Which change would shift the position of this equilibrium towards the products? H2(g) + I2(g) ⇌ 2 HI(g) ΔH = −9 kJ mol−1 A. Increase pressure B. Decrease pressure C. Increase temperature D. Decrease temperature
Zadanie 1e
The amount of NO2 prepared was checked by titration. The gas was first absorbed in water: 2 NO2(g) + H2O(l) → HNO3(aq) + HNO2(aq) The resulting solution was made up to 200.0 cm3 in a volumetric flask, and 20.0 cm3 portions…
- Tabela do uzupełnienia
Zadanie 1d
Cresolphthalein is a weak acid that can be represented as HIn. Using an equation, explain why the colour of a solution containing cresolphthalein depends on its pH.
- Materiał graficzny
Zadanie 2b
When potassium thiocyanate solution is added to a pale yellow solution containing iron(III) ions, the following equilibrium is established. [Fe(H2O)6]3+(aq) + SCN−(aq) ⇌ [Fe(SCN)(H2O)5]2+(aq) + H2O(l) [Fe(H2O)6]3+(aq) is pale yellow and…
Zadanie 3a
(i) An equilibrium mixture in a 25.0 dm3 reactor at 500 °C contains 15.0 mol N2, 22.5 mol H2 and 5.25 mol NH3. Calculate the equilibrium constant, K, for the reaction. (ii) The volume of the reactor containing the equilibrium…
- Materiał graficzny
Zadanie 29
The gas-phase decomposition below has reached equilibrium in a sealed vessel: PCl5(g) ⇌ PCl3(g) + Cl2(g) ΔH⊖ = +88 kJ mol−1 The pressure is then changed. Which row pairs the change correctly with the direction in which the…
Zadanie 29
Iron(III) ions and thiocyanate ions form a deep red complex ion in aqueous solution. Fe3+(aq) + SCN−(aq) ⇌ [Fe(SCN)]2+(aq) Which of the following correctly predicts the effect of a change on this equilibrium? A. Adding iron(III) nitrate solution…
Zadanie 30
The container holding the equilibrium mixture below is compressed to half its volume while the temperature is kept constant. Which row gives the change in the amount of PCl5 and the effect on the equilibrium constant, K?…
Zadanie 3c
(i) Sketch the Maxwell–Boltzmann distribution curve for 298 K on the same axes as the 800 K curve. (ii) On the graph, annotate the position corresponding to the activation energy, Ea. (iii) With reference to the graph, explain why a lower…
- Materiał graficzny
Zadanie 1b
The pool operators add sodium carbonate to the water to raise its pH. Explain why a larger proportion of the dissolved chlorine reacts with water after the sodium carbonate has been added.
Zadanie 1c
A student writing a report on chlorine as a disinfectant collects, from several websites and reference books, values for how much chlorine dissolves in pure water at various temperatures. (i) Identify one difficulty in comparing the solubility values from…
- Tabela do uzupełnienia
Zadanie 1g
Some users have asked for the water to be heated in winter. Suggest two reasons why leaving the water unheated is the better choice for the environment.
Zadanie 3c
Suggest two reasons why less carbon dioxide is collected in the syringe when a greater mass rests on the piston.
- Materiał graficzny
Zadanie 5g
The equilibrium constant, Kc, for the reaction in (f) is 6.4 × 10−5 at 80 °C. (i) 1.00 dm3 of a mixture that is initially 0.20 mol dm−3 in octadecanoic acid and 0.20 mol dm−3 in butan-2-ol is…
Zadanie 33
An indicator, HIn, is a weak acid with pKa = 5.0. HIn is yellow and its conjugate base, In−, is blue. HIn(aq) ⇌ H+(aq) + In−(aq) Which statements are correct? I. At pH 2.0 the indicator appears yellow. II. At pH 5.0 the…
Zadanie 3b
Predict, with a reason, the effect of increasing the total pressure, at constant temperature, on the position of equilibrium.
Zadanie 4d
State, with a reason, how the value of Kc changes when the temperature is raised, given that ΔH⊖ > 0.
Zadanie 4e
State, with a reason, how the position of this equilibrium is affected when aqueous silver nitrate, AgNO3(aq), is added. Ag+(aq) + Cl−(aq) → AgCl(s)
Zadanie 25
Which pair of changes will both shift the position of equilibrium to the left? CH4(g) + H2O(g) ⇌ CO(g) + 3 H2(g) ΔH = +206 kJ mol−1 A. Decrease the temperature and increase the pressure B. Increase the temperature and increase…
Zadanie 22
Ammonia dissolves in water as shown in the equation below. What will happen if the temperature of the solution is increased? NH3(g) + H2O(l) ⇌ NH4+(aq) + OH−(aq) ΔH⊖ = −31 kJ mol−1 A. The equilibrium shifts to the left…
Zadanie 10a
4-Nitrophenol is used as an acid-base indicator. It exists as two forms, X and Y, which differ in colour. Explain which form, X or Y, predominates at pH 11.
- Materiał graficzny
Zadanie 22
A saturated solution of magnesium hydroxide contains undissolved solid. Which change will shift the position of the equilibrium to the right? Mg(OH)2(s) ⇌ Mg2+(aq) + 2 OH−(aq) A. Adding more solid Mg(OH)2 B. Adding dilute hydrochloric acid C.…
Zadanie 2d
Suggest why the value of the equilibrium constant changes very little with temperature.
Zadanie 23
Which change would increase the amount of CO(g) in the equilibrium mixture below? CH4(g) + H2O(g) ⇌ CO(g) + 3 H2(g) ΔH⊖ = +206 kJ A. Adding a catalyst to the system B. Decreasing the volume of the reaction vessel C.…
Zadanie 23
The system below is at equilibrium. CH4(g) + H2O(g) ⇌ CO(g) + 3 H2(g) ΔH⊖ = +206 kJ Which change to the equilibrium mixture would produce more H2(g)? A. Adding a catalyst B. Increasing the pressure by decreasing the…
Zadanie 3b
The enthalpy change of the reaction is one factor that influences the position of equilibrium. (i) Determine the enthalpy change, ΔH, for the production of methanol, in kJ, using bond enthalpies. Use section 12 of the data booklet. (ii) Outline why a…
- Materiał graficzny
Zadanie 6b
(i) On the axes below, sketch Maxwell–Boltzmann energy distribution curves for the methanol molecules at two temperatures, T1 and T2, where T2 > T1. (ii) Explain the effect of increasing the temperature on the equilibrium yield of methanal.
- Materiał graficzny
Zadanie 24
What happens to the amount of hydrogen ions and to the hydrogen ion concentration when water is added to a solution of ethanoic acid, CH3COOH(aq)? A. n(H+) decreases; [H+] decreases B. n(H+) increases; [H+] decreases C.…
Zadanie 4a
(i) Deduce the structural formula and the empirical formula of B. (ii) Explain, with reference to Le Châtelier’s principle, the effect on the yield of B of using dilute rather than concentrated sulfuric acid as the catalyst. (iii) Compound A has a lower molar…
- Materiał graficzny
Zadanie 23
Iron(III) ions and thiocyanate ions react to form a blood-red complex ion. Fe3+(aq) + SCN−(aq) ⇌ [FeSCN]2+(aq) Which of these changes would shift the equilibrium to the right? I. Addition of solid potassium thiocyanate, KSCN II. Addition of…