Chemistry SL Paper 2, specimen 2025

Determine the empirical formula of HA.

A $20.00\ \mathrm{cm^3}$ sample of a solution containing 1.21 g of HA is titrated with $0.500\ \mathrm{mol\,dm^{-3}}$ sodium hydroxide solution, NaOH(aq). Exactly $27.40\ \mathrm{cm^3}$ of the NaOH(aq) is required to neutralize the acid completely. Determine…

State the molecular formula of HA.

HA is neutralized by potassium hydroxide solution according to the equation $\ce{HA(aq) + KOH(aq) -> KA(aq) + H2O(l)}$ Identify a functional group present in HA.

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:…

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 $\ce{Li^2+}$ ion, can be explained…

Outline why the scientific model of the atom has been modified several times since it was first proposed.

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.

Suggest why the times measured for equal masses of the two metals are not a valid basis for comparing their reactivity.

When sodium burns in excess oxygen, the main product is sodium peroxide, $\ce{Na2O2}$. Determine the percentage covalent character and the bonding type in sodium peroxide using sections 9 and 17 of the data booklet.

Sodium peroxide, $\ce{Na2O2}$, contains the peroxide ion. Draw the Lewis formula of this anion.

Write an equation for the complete combustion of $\ce{C19H40}$.

The enthalpy of combustion of $\ce{C19H40}$ is $-12\,660\ \mathrm{kJ\,mol^{-1}}$. (i) Calculate the maximum energy released when 1.50 g of $\ce{C19H40}$ is burned completely. (ii) Determine the maximum temperature increase when $400.0\ \mathrm{cm^3}$ of water…

Explain why a fuel produced from recently grown plants (a biofuel) contributes less to climate change than a fossil fuel.

In an oil refinery, nonadecane can be cracked into smaller molecules. Consider the reaction: $\ce{C19H40(g) -> 3C3H6(g) + C10H22(g)}$ Determine the standard enthalpy change, $\Delta H^\ominus$, for this reaction using section 12 of the data booklet.

Propene can be converted into propan-2-ol in a single reaction. State the equation for this conversion.

Propan-2-ol reacts with tetradecanoic acid to produce propan-2-yl tetradecanoate, an ester used in skin creams. $\ce{C13H27COOH(l) + CH3CH(OH)CH3(l) <=> C13H27COOCH(CH3)2(l) + X(l)}$ (i) Identify the by-product X(l). (ii) Calculate the atom economy of this…

(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,…

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…

Nitric acid is a strong acid manufactured on a large scale. A pH probe is immersed in a small volume of $0.010\ \mathrm{mol\,dm^{-3}}$ nitric acid. The pH is recorded while distilled water is added to the acid at a steady rate and at constant temperature. (i)…