Chemistry HL Paper 2, May 2025, TZ2

At room temperature hydrogen cyanide is a liquid that evaporates readily, whereas ethyne, $\ce{C2H2}$, which has almost the same molar mass, is a gas that boils at −84 °C. (i) Draw the Lewis formula of the hydrogen cyanide molecule, showing all valence…

In aqueous solution hydrogen cyanide behaves as a weak acid. (i) Write an equation for the ionization of hydrogen cyanide in water. (ii) Outline two ways in which a solution of 0.050 $\mathrm{mol\,dm^{-3}}$ $\ce{HCN}$ could be distinguished experimentally from…

The cyanide ion acts as a ligand in many complex ions, for example hexacyanoferrate(III), $\ce{[Fe(CN)6]^3-}$. (i) State the type of bond, as precisely as possible, that joins each cyanide ion to the iron ion. (ii) Deduce the oxidation state of iron in…

Cyanide ions react with bromoethane, $\ce{CH3CH2Br}$. (i) Draw the full structural formula of the organic product of this reaction. (ii) Predict which mechanism, $\mathrm{S_N1}$ or $\mathrm{S_N2}$, operates in this reaction, and give a reason for your choice.…

Naturally occurring gallium consists of two isotopes: 60 % of the atoms contain 38 neutrons and the remaining 40 % contain 40 neutrons. (i) Use section 7 of the data booklet to deduce the nuclear symbol of the heavier isotope. (ii) Calculate the relative…

Gallium forms a sulfate of formula $\ce{Ga2(SO4)3}$. (i) Both ionic and covalent bonding are present in this compound. State which particles are held together by each type of bond. (ii) Contrast covalent and ionic bonds in terms of what happens to the valence…

Gallium was discovered in 1875 from its atomic emission spectrum, which contains two strong violet lines. (i) State which feature of an emission spectrum allows the ionization energy of the element to be determined. (ii) Using sections 1, 2 and 9 of the data…

Suppose carbonyl dibromide were made by a free-radical chain reaction of carbon monoxide, $\ce{CO}$, with bromine vapour, $\ce{Br2}$, started by ultraviolet light. The questions below treat this hypothetical route with the bond-enthalpy model and the entropy…

In moist air carbonyl dibromide is slowly hydrolyzed: $\ce{Br2CO(g) + H2O(g) -> CO2(g) + 2HBr(g)}$ (i) Suggest a method of monitoring the progress of this reaction at constant temperature so that its rate can be determined. (ii) Outline two reasons why a…

The mass spectrum of carbonyl dibromide is shown below. Bromine has two isotopes, $\ce{^{79}Br}$ and $\ce{^{81}Br}$, of almost equal abundance. (i) Explain the origin of the peaks that appear at m/z values smaller than those of the molecular ion. (ii) Deduce…

The structure of galantamine is shown below. (i) State the name of the functional group that contains the nitrogen atom. (ii) Outline the effect of this functional group on the pH of water in which galantamine is dissolved, giving the direction of the change…

A chemist treated 22.99 g of galantamine with sulfuric acid to make the sulfate salt: $\ce{2C17H21NO3 + H2SO4 -> (C17H22NO3)2SO4}$ The mass of salt isolated was 24.65 g. Determine the percentage yield of the salt. Use section 7 of the data booklet.