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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…
Which row correctly states the types of intermolecular force present between molecules of ethane, methylamine and fluoromethane? A. Ethane: London (dispersion) forces only; methylamine: London forces, dipole-dipole forces and hydrogen bonding; fluoromethane:…
The structure of a compound is shown below. Atom (1) is the nitrogen atom of the ring, atom (2) is the ring carbon bonded to the ethynyl group and atom (3) is the terminal carbon of the ethynyl group. Which row gives the hybridization and the molecular…
How many sigma (σ) bonds and how many pi (π) bonds does one molecule of the compound below contain? HC≡C−CH=CH−C≡N A. 5 σ and 8 π B. 8 σ and 5 π C. 9 σ and 5 π D. 13 σ and 5 π
Which statements about alloys are correct? I. Alloys can contain non-metallic elements as well as metals. II. Alloys are usually softer than the pure metals they contain, because their layers slide over each other more easily. III. Atoms of different sizes…
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,…
The decomposition of calcium carbonate is not spontaneous at low temperatures but is spontaneous at high temperatures. CaCO3(s) → CaO(s) + CO2(g) What are the signs of ΔH⊖ and ΔS⊖ for this reaction?…
A lithium-ion cell in a mobile phone can be recharged, but a zinc–carbon cell in a torch cannot. Outline why.
Consider the following equations. H2(g) + Cl2(g) → 2 HCl(g) ΔH⊖ = −x kJ C(s) + 2 Cl2(g) → CCl4(g) ΔH⊖ = −y kJ 2 C(s) + H2(g) → C2H2(g) ΔH⊖ = +z kJ What…
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…