Zadania wzorowane na pytaniach z tego arkusza: te same umiejętności, format i punktacja, inne dane i kontekst. Treści arkusza IB nie publikujemy.
Dodaj cały arkusz do zestawuYoung mussels were placed in a contaminated harbour. Samples were taken at regular intervals and the tin content of the soft tissue was determined. (i) The tin content follows a linear trend during the first six weeks. Deduce the equation for this part of the…
The concentration of tin in a sample of mussel tissue is 0.0064 ± 0.0002 mg Sn g−1. (i) Calculate the mass of tin, in mg, in 2.416 g of the sample. (ii) Calculate the percentage uncertainty of the concentration.
Suggest two variables that should be controlled when mussels are collected and their soft tissue is sampled.
Suggest why it is important that hydrogen gas flows through the tube (i) before heating begins, (ii) from the end of heating until the product has cooled.
(i) State which two further mass measurements are needed to find the oxide composition. (ii) Outline how these measurements give the mass of oxygen removed from the sample.
Suggest why the amount of oxygen per mole of iron calculated from the results is often lower than the true value, and how this error could be reduced.
Chromium(III) oxide, Cr2O3, is a hard ceramic used as an abrasive and as a wear-resistant coating. Outline the bonding in chromium(III) oxide and its electrical conductivity in the solid state. Use sections 9 and 17 of the data booklet.
A conductivity probe is used to follow the concentration of sodium chloride in dilute aqueous solutions. A solution of concentration 0.015 mol dm−3 gives a conductivity of 1.8 mS cm−1. On the axes, draw a graph of conductivity…
Bronze, an alloy of copper and tin, is used for ship propellers and bearings. Explain, by referring to its structure, why bronze is less malleable than pure copper.
Boron trifluoride, BF3, reacts with ammonia to form the adduct F3B−NH3, in which a coordination bond joins the boron atom to the nitrogen atom. Deduce whether the boron atom in BF3 acts as a nucleophile or an electrophile, and as a Lewis…
Nylon-6,6 is a polyamide used to make strong fibres. A section of one chain is shown; asterisks indicate continuation bonds. Compare and contrast the bonding and the intermolecular forces in nylon-6,6 and in graphite.
Iron(III) ions catalyse the decomposition of hydrogen peroxide but zinc ions do not. Outline why.
Beeswax contains esters that form when long-chain carboxylic acids react with long-chain alcohols. State the name of this type of reaction.
Fructose, C6H12O6, exists mainly as a ring, but a small proportion of the molecules in solution are in the straight-chain form shown. State the names of the functional groups present in the straight-chain form of fructose.
The concentration of copper(II) ions in wastewater from a plating works was determined by colorimetry. Excess ammonia solution was added to each solution so that all the copper(II) ions formed the deep blue complex ion [Cu(NH3)4]2+, and the absorbance…
Petrol (gasoline) is a mixture of hydrocarbons and can be blended with bioethanol. The carbon footprint of a fuel can be expressed as the mass of carbon dioxide, in kg, produced per kg of fuel burned. (i) Calculate the carbon footprint of heptane,…
A lithium-ion cell in a mobile phone can be recharged, but a zinc–carbon cell in a torch cannot. Outline why.
Ethyl 4-hydroxybenzoate is a preservative used in some oral medicines. It was synthesized by heating 0.745 g of 4-hydroxybenzoic acid with excess ethanol and a few drops of concentrated sulfuric acid as catalyst. C7H6O3 + C2H6O ⇌ C9H10O3 + H2O Mr…
Menthol, used in medicinal rubs, has several chiral carbon atoms in its ring, which is numbered below. Draw circles around two chiral carbon atoms in this structure.
A pharmaceutical chemist has a reference sample of the desired enantiomer of a chiral drug. Explain how a polarimeter can help establish whether a newly prepared sample contains that enantiomer.
Some antacid tablets contain aluminium hydroxide. Write an equation for the neutralization reaction between aluminium hydroxide and stomach acid (hydrochloric acid).
A liquid medicine is buffered with carbonate ions and hydrogencarbonate ions. It contains 0.0120 mol dm−3 carbonate ions and 0.0300 mol dm−3 hydrogencarbonate ions. Ka (hydrogencarbonate ion) = 4.80 × 10−11.…