Zadanie 1a
Determine the empirical formula of HA.
Chemistry SL Paper 2, specimen 2025
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Dodaj cały arkusz do zestawuZadanie 1b
A 20.00 cm3 sample of a solution containing 1.21 g of HA is titrated with 0.500 mol dm−3 sodium hydroxide solution, NaOH(aq). Exactly 27.40 cm3 of the NaOH(aq) is required to neutralize the acid completely. Determine…
Zadanie 1c
State the molecular formula of HA.
Zadanie 1d
HA is neutralized by potassium hydroxide solution according to the equation HA(aq) + KOH(aq) → KA(aq) + H2O(l) Identify a functional group present in HA.
Zadanie 2a
In the Geiger–Marsden experiment, α-particles (the nuclei of helium-4 atoms) were fired at a very thin foil of silver. A detector that could be moved around the foil recorded the angle of deflection, θ, of the particles. Two of the possible routes are shown:…
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Zadanie 2b
Lithium can be identified in the light emitted by stars and by flames containing lithium compounds. (i) Outline the appearance of the emission spectrum of lithium. The emission spectrum of a one-electron species, such as the Li2+ ion, can be explained…
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Zadanie 2c
Outline why the scientific model of the atom has been modified several times since it was first proposed.
Zadanie 3a
Sketch, on the axes, the graphs of the time for complete reaction against the mass of metal that you would expect for sodium and for potassium. Label each line.
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Zadanie 3b
Suggest why the times measured for equal masses of the two metals are not a valid basis for comparing their reactivity.
Zadanie 3c
When sodium burns in excess oxygen, the main product is sodium peroxide, Na2O2. Determine the percentage covalent character and the bonding type in sodium peroxide using sections 9 and 17 of the data booklet.
Zadanie 3d
Sodium peroxide, Na2O2, contains the peroxide ion. Draw the Lewis formula of this anion.
Zadanie 4a
Write an equation for the complete combustion of C19H40.
Zadanie 4b
The enthalpy of combustion of C19H40 is −12 660 kJ mol−1. (i) Calculate the maximum energy released when 1.50 g of C19H40 is burned completely. (ii) Determine the maximum temperature increase when 400.0 cm3 of water…
Zadanie 4c
Explain why a fuel produced from recently grown plants (a biofuel) contributes less to climate change than a fossil fuel.
Zadanie 4d
In an oil refinery, nonadecane can be cracked into smaller molecules. Consider the reaction: C19H40(g) → 3 C3H6(g) + C10H22(g) Determine the standard enthalpy change, ΔH⊖, for this reaction using section 12 of the data booklet.
Zadanie 4e
Propene can be converted into propan-2-ol in a single reaction. State the equation for this conversion.
Zadanie 4f
Propan-2-ol reacts with tetradecanoic acid to produce propan-2-yl tetradecanoate, an ester used in skin creams. C13H27COOH(l) + CH3CH(OH)CH3(l) ⇌ C13H27COOCH(CH3)2(l) + X(l) (i) Identify the by-product X(l). (ii) Calculate the atom economy of this…
Zadanie 5a
(i) Write an equation for the homolytic fission of a bromine molecule under UV light, using curly arrows to show the movement of electrons. (ii) Under different conditions a bromine molecule can undergo heterolytic fission. Write an equation for this process,…
Zadanie 5b
The graph shows the boiling points of five straight-chain carboxylic acids and of the five methyl esters that have the same relative formula masses as the acids. (i) Outline why the carboxylic acids have higher boiling points than the esters with the same…
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Zadanie 5c
Nitric acid is a strong acid manufactured on a large scale. A pH probe is immersed in a small volume of 0.010 mol dm−3 nitric acid. The pH is recorded while distilled water is added to the acid at a steady rate and at constant temperature. (i)…
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