A learner needs to smell a gas produced in a test tube. Which procedure is the safest laboratory practice?
Laboratory Skills
Question · Easy
Which statement correctly compares particles in a solid with particles in a gas at the same temperature?
Matter
Brownian motion of smoke particles in air is evidence that
Which technique is most suitable for separating an insoluble solid from a liquid, such as sand from water?
In the Ministry of Education Ordinary Level Chemistry syllabus, an element is best described as a substance that
On a heating curve of a pure solid, the temperature stays constant while the solid melts. Why does the temperature not rise during this stage?
Question · Medium
A sample of a solid melts over a wide temperature range rather than at one sharp melting point. The most likely explanation is that the sample is
Which subatomic particle has a relative charge of −1 and a relative mass that is treated as negligible at Ordinary Level?
Atomic Structure
A sodium atom is written as ²³Na and has atomic number 11. How many neutrons are in the nucleus?
Isotopes of the same element have
What is the electron arrangement of a neutral chlorine atom (atomic number 17) using the 2,8,8 shell-filling used at Ordinary Level?
In nuclide notation ¹⁴₆C, what do the numbers 14 and 6 represent?
A chloride ion, Cl⁻, is formed from a chlorine atom (atomic number 17). How many electrons does the ion contain?
Chlorine has two isotopes. A sample contains 75.0% ³⁵Cl and 25.0% ³⁷Cl. What is the relative atomic mass of chlorine in this sample?
Question · Hard
Which use of a radioisotope is correctly matched with a genuine hazard that must be managed?
Elements in the same group of the Periodic Table have similar chemical properties mainly because they have
Periodic Table
Across Period 3 from sodium to chlorine, which trend is correct?
Why does the reactivity of Group I metals increase from lithium to potassium?
Which statement about Group VII (the halogens) is correct?
Argon is used in some types of welding. The chemical reason is that argon
Which pair correctly describes metallic character in the Periodic Table?
Element X is in the same group as chlorine and is in the period below chlorine. Which property is X most likely to show?
An ionic (electrovalent) bond is best described as
Bonding
A covalent bond is formed when
Metallic bonding is the electrostatic attraction between
Why does solid sodium chloride not conduct electricity, while molten sodium chloride does?
Diamond and silicon(IV) oxide both have very high melting points. The best explanation is that both substances
Iodine, I₂, is a solid at room temperature but melts easily on gentle heating. This is because iodine
Aluminium forms a 3+ ion and oxygen forms a 2− ion. What is the chemical formula of aluminium oxide?
Graphite conducts electricity but diamond does not, even though both are giant covalent forms of carbon. The best explanation is that
The reaction 2HgO(s) → 2Hg(l) + O₂(g) is an example of
Chemical Reactions
In a balanced chemical equation the state symbol (aq) means the substance is
Iron burns in oxygen to form iron(III) oxide. Which equation is correctly balanced?
Aluminium oxide reacts with both hydrochloric acid and sodium hydroxide. This behaviour classifies Al₂O₃ as
Acids Bases Salts
Using A_r(H) = 1, A_r(S) = 32 and A_r(O) = 16, what is the relative formula mass of H₂SO₄?
Stoichiometry
A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Using A_r(C) = 12, A_r(H) = 1 and A_r(O) = 16, what is its empirical formula?
A compound has empirical formula CH₂O and a relative molecular mass of 60. What is its molecular formula? (A_r: C = 12, H = 1, O = 16)
How many moles of methane, CH₄, are in 8.0 g of the gas? (A_r: C = 12, H = 1)
How many molecules are in 0.250 mol of carbon dioxide? (Avogadro constant L = 6.02 × 10²³ mol⁻¹)
What volume does 0.250 mol of oxygen gas occupy at room temperature and pressure? (Molar volume at r.t.p. = 24.0 dm³ mol⁻¹)
0.100 mol of sodium hydroxide is dissolved and the solution made up to 250 cm³. What is the concentration of the solution?
Calcium carbonate decomposes on heating: CaCO₃(s) → CaO(s) + CO₂(g). What volume of carbon dioxide, measured at r.t.p., is produced from 25.0 g of CaCO₃? (A_r: C = 12, O = 16, Ca = 40; V_m = 24.0 dm³ mol⁻¹)
Hydrogen and oxygen react: 2H₂(g) + O₂(g) → 2H₂O(l). A mixture contains 4.0 g of H₂ and 16 g of O₂. What mass of water can form? (A_r: H = 1, O = 16)
CuO(s) + H₂(g) → Cu(s) + H₂O(l). Reduction of 8.00 g of copper(II) oxide gives 5.76 g of copper. What is the percentage yield? (A_r: O = 16, Cu = 64)
What is the percentage by mass of oxygen in water, H₂O? (A_r: H = 1, O = 16)
12.5 g of hydrated copper(II) sulfate, CuSO₄·xH₂O, is heated to constant mass. 8.00 g of anhydrous CuSO₄ remains. What is the value of x? (A_r: H = 1, O = 16, S = 32, Cu = 64)
Magnesium reacts with dilute hydrochloric acid: Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g). What volume of hydrogen, at r.t.p., is produced from 0.24 g of magnesium? (A_r(Mg) = 24; V_m = 24 dm³ mol⁻¹)
25.0 cm³ of 0.100 mol/dm³ sulfuric acid is exactly neutralised by 20.0 cm³ of sodium hydroxide. The equation is H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O. What is the concentration of the sodium hydroxide?
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