Zadanie 1a
Determine the empirical formula of HA from the percentage composition.
Chemistry HL Paper 2, specimen 2025
Zadania wzorowane na pytaniach z tego arkusza: te same umiejętności, format i punktacja, inne dane i kontekst. Treści arkusza IB nie publikujemy.
W bazie 23 zadania z tego arkusza, razem 90 punktów, każde z kluczem i schematem punktowania. Najwięcej zadań sprawdza: Empirical and molecular formulas (2), Functional groups in organic compounds (2), Infrared spectra and functional groups (2).
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Dodaj cały arkusz do zestawuZadanie 1b
A solution is prepared by dissolving 1.29 g of HA in water and making the volume up to 20.00 cm3. When the whole of this solution is titrated with 0.600 mol dm−3 sodium hydroxide, NaOH(aq), exactly 24.90 cm3 of the…
Zadanie 1c
State the molecular formula of HA, using your answers to (a) and (b).
Zadanie 1d
HA reacts with aqueous sodium carbonate according to the equation: 2 HA(aq) + Na2CO3(aq) → 2 NaA(aq) + CO2(g) + H2O(l) Identify the functional group in HA that is responsible for this reaction.
Zadanie 1e
The IR spectrum of HA is shown. Two absorption bands are labelled: Y is a very broad band centred near 3000 cm−1 and Z is a band of medium intensity near 1650 cm−1. (i) Using section 20 of the data booklet, identify the functional…
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Zadanie 2a
α-particles are the nuclei of helium-4 atoms. In an experiment based on the work of Geiger and Marsden, a beam of α-particles is directed at a very thin platinum foil and the angle of deflection, θ, of each particle is recorded by a detector that can be moved…
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Zadanie 2b
The presence of hydrogen in stars is deduced from lines in their spectra. (i) Outline what the emission spectrum of hydrogen looks like. Emission spectra of species that contain a single electron can be explained by a model in which the electron is held by the…
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Zadanie 2c
Outline why scientists have replaced earlier models of the atom with new ones.
Zadanie 3a
Below is a sodium-ion cell as it discharges, supplying a current to an external circuit. The anode is sodium held in a lattice of hard carbon and the cathode is iron(III) phosphate, FePO4, which is converted to NaFePO4 as the cell discharges.…
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Zadanie 3b
When the cell discharges, a spontaneous redox reaction generates a potential difference between the electrodes and the temperature of the cell rises. (i) Deduce the signs of ΔHdischarge, Ecell and ΔGdischarge.…
Zadanie 3c
A computer simulation models what happens when small pieces of lithium and of sodium are dropped into water. For each metal five pieces of increasing mass are used, the same set of masses for both metals, and the simulation records how long each piece takes to…
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Zadanie 4a
A small volume of 0.050 mol dm−3 hydrobromic acid is placed in a beaker fitted with a pH probe. Distilled water is then run into the beaker at a constant rate and the pH is logged continuously; the temperature is held at 298 K. (i) Sketch, on…
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Zadanie 4b
Chloride ions can act as ligands towards transition metal ions. Three compounds of chromium that differ in the number of chloride ions bonded directly to the chromium ion have the formulas and colours shown. (i) Deduce the charge of the complex ion in…
- Tabela do uzupełnienia
Zadanie 5a
Complete combustion turns pentadecane entirely into carbon dioxide and water. Write the corresponding balanced equation.
Zadanie 5b
The enthalpy of combustion of C15H32 is −10 040 kJ mol−1. (i) Calculate the maximum amount of energy that the complete combustion of 1.75 g of pentadecane can release. (ii) The energy from burning the 1.75 g sample is used to heat…
Zadanie 5c
Pentadecane produced by cyanobacteria can be used as a biofuel. Explain why burning this biofuel adds less to the long-term buildup of atmospheric carbon dioxide than burning the same mass of pentadecane refined from crude oil.
Zadanie 5d
Pentadecane can be cracked into smaller molecules. Consider the reaction: C15H32(g) → 3 C4H8(g) + C3H8(g) where C4H8 is but-1-ene. (i) Use the bond enthalpies in section 12 of the data booklet to determine ΔH⊖ for this reaction.…
Zadanie 5e
But-1-ene is converted into butan-2-ol in a single reaction. State the corresponding equation.
Zadanie 5f
Butan-2-ol reacts with octadecanoic (stearic) acid to form an ester that is used as a lubricant. C17H35COOH(l) + CH3CH(OH)CH2CH3(l) ⇌ C17H35COOCH(CH3)CH2CH3(l) + X(l) (i) Identify the by-product X(l) and state the type of reaction taking place. (ii)…
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 6a
(i) Iodine molecules, I2, undergo homolytic fission when they absorb light. Write an equation for this process, using curly arrows to show the movement of the electrons. (ii) In the presence of a suitable reagent the I–I bond can instead break…
Zadanie 6b
The boiling points of the five simplest straight-chain primary amines, CH3NH2 to CH3(CH2)4NH2, and of the five simplest 1-fluoroalkanes, CH3F to CH3(CH2)4F, are plotted below against the number of carbon atoms in the molecule. An…
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Zadanie 6c
(i) Draw the structural formula of 2-chloropentane and that of the structural isomer in which the chlorine atom is attached to a tertiary carbon atom. (ii) Only one of the two isomers drawn in (c)(i) is chiral. Draw stereochemical formulas showing its two…
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