2021 O Level Pure Chemistry Paper 1 — All Solutions

A student follows the rate of the reaction when 0.19 g of magnesium reacts with excess acid at room temperature and pres…

The boiling points of some of the substances found in air are: argon −186 °C, neon −246 °C, nitrogen −196 °C and oxygen …

An aqueous solution of a salt is tested. When a few drops of aqueous sodium hydroxide are added, a white precipitate for…

The rate of diffusion of five gases is measured. The gases are CO, CO₂, C₂H₄, C₃H₈ and N₂. The list gives four pairs of …

An atom of one isotope of bromine is represented by the symbol ⁸¹₃₅Br. Which row is correct for an atom of a different i…

Some properties of four substances are shown in the table. Which substance is silver chloride?…

The following all contain covalent bonds: 1 ammonia, 2 carbon dioxide, 3 ethanol. Which contain only single covalent bon…

Which statements about metals are correct? 1 Metals are not malleable. 2 Metals conduct thermal energy. 3 Metals have a …

Basic copper carbonate, Cu₂CO₃(OH)₂, is used as a pigment in paint. What is the percentage by mass of copper in basic co…

Analysis of molecule X shows that it contains, by mass, 52% carbon, 13% hydrogen and 35% oxygen. Which information is ne…

An excess of dilute sulfuric acid is added separately to the following reagents. Reaction 1: 1.2 g of magnesium. Reactio…

Which volume of carbon dioxide gas, at room temperature and pressure, is produced when 2.65 g of sodium carbonate reacts…

A concentrated aqueous solution containing each of the following ions, Cl⁻, SO₄²⁻, Na⁺ and Cu²⁺, is electrolysed using p…

Methane burns in oxygen to form carbon dioxide and water. The energy profile diagram for the reaction is shown. Which st…

Iron reacts with dilute hydrochloric acid at a constant temperature of 25 °C. Which statement about the rate of this rea…

Chlorine is reacted with aqueous potassium iodide and a brown solution is formed. Which statement about this reaction is…

Beryllium hydroxide is an amphoteric white solid. Which reagent can be used to distinguish beryllium hydroxide from soli…

Salt P can be prepared by reacting together either a dilute acid and a metal, or an acid and an insoluble carbonate. A p…

The energy profile diagram for the formation of ammonia is shown. The reaction ½N₂ + 1½H₂ → NH₃ is exothermic, releasing…

A small piece of lithium is added to aqueous ammonium chloride. Two gases are produced and tested. Which row identifies …

The table shows data for atoms or ions of the elements P, Q, R and S. The letters do not represent the chemical symbols …

Arc welding is a process which uses electricity to make high temperatures to melt two pieces of metal so that they can b…

Which statements about the Group VII elements are correct? 1 Bromine reacts with iodide ions to form iodine. 2 The eleme…

An ionic chloride of element Z has the formula ZCl. When ZCl is added to water and swirled, a coloured solution appears …

The arrangement of atoms in pure iron is shown. Steel can be made by adding carbon to pure iron. Which description of th…

Copper(II) oxide is reduced to copper as shown. Dry hydrogen is passed over heated copper(II) oxide, with the excess hyd…

Which metal forms the most thermally stable carbonate?…

Iron can be protected from rusting by galvanising and by sacrificial protection. Which reactions take place in either or…

The depletion of the ozone layer can result in an increase in cases of skin cancer. What is the reason for this?…

Which row shows air pollutants and their sources correctly?…

Acidified potassium manganate(VII) changes from purple to colourless when it is added to substance X. What can be determ…

Propene is used to make poly(propene). Which fraction from petroleum is the main feedstock for the manufacture of propen…

Which equations are correct for alkanes burning in air? 1 C₃H₈ + 5O₂ → 3CO₂ + 4H₂O. 2 C₄H₈ + 5O₂ → 4CO₂ + 4H₂O. 3 C₂H₆ +…

Which statements about the formulae of some organic compounds are correct? 1 The general formula of an alkane is CₙH₂ₙ₊₂…

Which structure is an isomer of butane?…

X reacts with steam to form Y. Y is oxidised to Z. If Z is propanoic acid, what is the formula of X?…

Addition of hydrogen to an unknown alkene gives the alkane (CH₃)₃CH. What is the unknown alkene?…

Statins are compounds used in some medicines. An example of a statin is shown. Which part of the structure shows the fun…

Q is a compound that forms a gas when added to aqueous sodium carbonate. What is true about Q?…

The table refers to the polymers nylon and poly(ethene). Which row is correct?…