Chemistry SL Paper 1A, specimen 2025

Which technique is used to obtain pure water from a solution of sodium chloride in water? A. evaporation B. distillation C. filtration D. paper chromatography

At 25 °C the density of heavy water, $\ce{^{2}H2O(l)}$, is $1.11\ \mathrm{g\,cm^{-3}}$, while the density of ordinary water, $\ce{^{1}H2O(l)}$, is $1.00\ \mathrm{g\,cm^{-3}}$. Which statement explains this difference? A. Each $\ce{^{2}H}$ nucleus contains one…

Which electron transition in a hydrogen atom emits radiation with the longest wavelength? A. $n = 2$ to $n = 1$ B. $n = 3$ to $n = 2$ C. $n = 4$ to $n = 3$ D. $n = 1$ to $n = 4$

A sealed flask contains 8.0 g of helium and 120 g of argon. What is the ratio of the number of atoms of argon to the number of atoms of helium in the flask? A. 0.067 B. 0.67 C. 1.5 D. 15

A rigid cylinder of fixed volume contains $N$ molecules of an ideal gas at 200 K and a pressure of 80 kPa. Half of the molecules are removed and the temperature of the remaining gas is raised to 500 K. What is the new pressure of the gas, in kPa? A. 16 B. 40…

What is the formula of the compound formed between aluminium ions and sulfate ions? A. $\ce{AlSO4}$ B. $\ce{Al2(SO4)3}$ C. $\ce{Al(SO4)3}$ D. $\ce{Al3(SO4)2}$

Which species contains a coordination bond? A. $\ce{NH3}$ B. $\ce{H3O+}$ C. $\ce{CH4}$ D. $\ce{BF3}$

Which properties of copper depend on the movement of its delocalized electrons? I. electrical conductivity of the molten metal II. thermal conductivity III. high density A. I and II only B. I and III only C. II and III only D. I, II and III

The table shows the average electronegativity and the electronegativity difference for four substances, each made from two elements. Substance Average electronegativity Electronegativity difference P 3.3 0.3 Q 2.0 2.3 R 1.4 0.3 S 2.7 1.1 Which substance is an…

Which structure shows the repeating unit of the addition polymer formed from pent-1-ene? A. $\ce{[CH2-CH2-CH(CH2CH3)]_n}$ B. $\ce{[CH(CH3)-CH(CH2CH3)]_n}$ C. $\ce{[CH2-CH(CH2CH2CH3)]_n}$ D. $\ce{[CH2-C(CH3)(CH2CH3)]_n}$

What is the explanation for the ductility of copper, which allows it to be drawn into wires? A. The attraction between the cations and the delocalized electrons is weak. B. The cations are held in the lattice by strong bonds that act in fixed directions. C.…

Which functional groups are present in this molecule? A. halogeno, carboxyl, hydroxyl B. halogeno, carbonyl, hydroxyl C. halogeno, carbonyl, alkoxy D. halogeno, ester, hydroxyl

Element 117, tennessine, was first synthesized in 2010. In which block of the periodic table is it placed? A. s B. p C. d D. f

Which is a correct alternative representation of the molecule shown? A. $\ce{C5H11Br}$ B. 3-bromo-2-methylbut-1-ene C. $\ce{CH2=CHC(CH3)2Br}$ D. $\ce{CH3CH=C(CH3)CH2Br}$

The periodic table is divided into the s, p, d and f blocks. Which characteristic of an element determines the block in which it is placed? A. the number of protons in its nucleus B. the sublevel occupied by its highest-energy electrons C. the number of main…

The enthalpy change of a reaction is $\Delta H = +58\ \mathrm{kJ\,mol^{-1}}$. Which statement about this reaction is correct? A. The reaction is endothermic and the products are less stable than the reactants. B. The reaction is endothermic and the products…

For which reactions can the enthalpy change be calculated using only average bond enthalpy data? I. $\ce{N2(g) + O2(g) -> 2NO(g)}$ II. $\ce{C2H4(g) + H2(g) -> C2H6(g)}$ III. $\ce{2H2O2(l) -> 2H2O(l) + O2(g)}$ A. I and II only B. I and III only C. II and III…

Which energy source is renewable? A. natural gas B. biodiesel made from vegetable oil C. petrol (gasoline) refined from crude oil D. uranium

Ammonia is oxidized according to the equation below. $\ce{4NH3(g) + 5O2(g) -> 4NO(g) + 6H2O(g)}$ What is the amount, in mol, of $\ce{H2O}$ produced when 8.00 mol of $\ce{NH3}$ reacts with 5.00 mol of $\ce{O2}$, if the yield is 80 %? A. 4.80 B. 6.00 C. 9.60 D.…

When $10.0\ \mathrm{cm^3}$ of a gaseous hydrocarbon, $\ce{C_xH_y}$, is burned completely, $70.0\ \mathrm{cm^3}$ of gaseous products is formed. This volume falls to $30.0\ \mathrm{cm^3}$ when the water vapour condenses. All volumes are measured at the same…

Propane hydrate, $\ce{C3H8.17H2O}$ ($M_r = 350$), is a crystalline solid that can form in natural gas pipelines at low temperature. What mass of carbon dioxide is produced by the complete combustion of 17.5 g of propane hydrate? A. 2.20 g B. 6.60 g C. 17.5 g…

The diagram shows the energy profile of a reaction. P, Q and R are energies measured from the baseline of the potential energy axis. Which combination gives the activation energy of the forward reaction and the activation energy of the reverse reaction? A.…

The rate of the reaction between hydrogen and iodine vapour increases markedly when the temperature is raised from 500 K to 550 K. What is the main reason for this increase? A. The activation energy of the reaction is lowered. B. Molecules collide more…

What is the equilibrium constant expression for the following reaction? $\ce{CH4(g) + H2O(g) <=> CO(g) + 3H2(g)}$ A. $\dfrac{[\ce{CH4}][\ce{H2O}]}{[\ce{CO}][\ce{H2}]^3}$ B. $\dfrac{3[\ce{CO}][\ce{H2}]}{[\ce{CH4}][\ce{H2O}]}$ C.…

Which reactions involve the transfer of a proton? I. $\ce{H2SO4(aq) + Zn(OH)2(s) -> ZnSO4(aq) + 2H2O(l)}$ II. $\ce{H2SO4(aq) + ZnCO3(s) -> ZnSO4(aq) + H2O(l) + CO2(g)}$ III. $\ce{H2SO4(aq) + Zn(s) -> ZnSO4(aq) + H2(g)}$ A. I and II only B. I and III only C. II…

Calcium hydride is used as a portable source of hydrogen for fuel cells. It reacts with water as shown. $\ce{CaH2(s) + 2H2O(l) -> Ca(OH)2(aq) + 2H2(g)}$ Which statement is correct? A. Calcium is reduced from +2 to 0. B. Hydrogen in $\ce{CaH2}$ is oxidized from…

In a redox titration, dichromate(VI) ions are reduced to chromium(III) ions and iron(II) ions are oxidized to iron(III) ions. $\ce{Cr2O7^2-(aq)}$ reduced to $\ce{Cr^3+(aq)}$ $\ce{Fe^2+(aq)}$ oxidized to $\ce{Fe^3+(aq)}$ What volume, in $\mathrm{cm^3}$, of…

What is the organic product of the reaction of 2-bromobutane with aqueous potassium hydroxide? A. but-1-ene B. butan-1-ol C. butan-2-ol D. 2-bromobutan-2-ol

Methane reacts with chlorine in the presence of ultraviolet light. Two observations about this reaction are listed. - Observation 1: in the initiation step, $\ce{Cl-Cl}$ bonds undergo homolytic fission but $\ce{C-H}$ bonds do not. - Observation 2: the…

Which species can act as an electrophile? A. $\ce{CN-}$ B. $\ce{NH3}$ C. $\ce{Br2}$ D. $\ce{Br-}$