Chemistry Questions

Nigel Li
Flashcards by Nigel Li, updated more than 1 year ago
Nigel Li
Created by Nigel Li over 5 years ago
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A deck of questions related to chemistry in the HKDSE syllabus

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Question Answer
What are isotopes? Isotopes are atims of the same element with the same number of protons and electrons while having different number of neutrons.
What is the chemical nature of rust? Hydrated Iron(III) oxide, Fe2O3•nH2O
What are Soluble Salts? Soluble salts are strong electrolytes containing mobile ions which can increase the electrical coductivity. e.g.: Fe will form Fe2+ ions more readily
What does the rust indicator contain? Potassium hexacyanoferrate(III) and phenolphthalein
What are acids? An acid is a hydrogen-containing covalent molecular compound that gives hydrogen ion (H+(aq)) as the ONLY positively charged ions (cation) when dissolved in water.
What is a base? A base is a compound that contains oxide ion(O2-) or hydroxide ion(OH-) and reacts with an acid to form a salt and water ONLY.
What is an Alkali? An alkali is a base soluble in water with ONLY hydroxide ion (OH-) released as the anion when dissolved in water.
What is the basicity of an acid? The basicity of an acid is the maximum number of ionisable hydrogen atom in an acid molecule. Monobasic: 1 ionisable hydrogen atom per acid molecule Dibasic: 2 ionisable hydrogen atom per acid molecule Tribasic: 3 ionisable hydrogen atom per acid molecule
What is pH? pH= -log[H+(aq)]
What is Neutralisation? Neutralisation is the reaction between the hydrogen ion from an acid and the hydroxide ion or the oxide ion from a base to form water and salt ONLY.
What is the nature of neutralisation? Exothermic Depending Factors: 1.No. of moles of water released 2. strength of acid and alkali
What are the application of neutralisation? 1. Soil pH control 2. Neutralise excess acid in stomach 3. Industrial Waste Water Disposal 4. Fertiliser production 5. Scrubbers
What is petroleum? Petroleum is a mixture of aliphatic(冇 benzene ring) and aromatic(有 benzene ring) hydrocarbons.
What are the major sources of air pollutants? Carbon monoxide(CO), Sulphur Dioxide(SO2), Nitrogen oxides(NO/NO2), Particulates, and Unburned hydrocarbons.
What are the measures to reduce air pollutants from burning fossil fuels? Catalytic converters, Scrubbers, and electrostatic precipitators
State two characteristics of members of a Homologous series? The members can be represented by the SAME general formula. There are gradual changes in physical properties among the member of a homologous series.
What is cracking? Cracking is the breaking down of large hydrocarbon molecule into small hydrocarbon molecules.
What is addition polymerisation? Addition polymerisation is a process that involves breaking of C=C double bonds in small alkene molecules.
What is electronegativity? Electronegativity of an atom is the ability of that atom to attract bonfing electrons to itself in a covalent bond.
What are the factors affecting the strength of Van der Waals' forces? 1. Size of molecules(vdw increase w/ no.of electrons) 2. Contact surface area of molecules(vdw increase w/ contact surface area) 3. Polarity of molecules(polar attraction forces)
What elements can form H-bond with hydrogen atoms? Nitrogen(N), Oxygen(O), and Fluorine(F)
What are the boiling point variations between hydrogen-bonded hydrides? H2O>HF>NH3
Why is the order like this in the last question? Each H2O molecules can form 2 H-bond while HF and NH3 can only form 1. F is more electronegative than N. Thus the H-bond between HF molecules is stronger than that between NH3 molecules.
Why does ice have a lower density than liquid water? The inter molecular attraction in both ice and liquid water is mainly hydrogen bonding. The directional character of hydrogen bonding makes the H2O molecules in ice arrange tetrahredrally to form a open structure. The open structure collapses when ice melts. H2O molecules packed more closely together than liquid water than in ice.
What is the difference between primary and secondary cells? Primary cell is unable to be recharged while sdcondary cells can.
What are the characteristics of primary cells?
What are the characteristics of secondary cells?
What are tue problems with chemical cell with 2 metal electrodes and 1 electrolyte? 1. Displacement reaction may occur on electrode surface 2. Colourless gas bubbles may evolve.
What are the functions of salt bridge? 1. To complete the curcuit by allowing the flow of mobile ions between the two half-cells. 2. Also, it is to provide mobile ions to balance the charges in the solutions of the two half-cells.
What is oxidation? Oxidation is the loss of electron by an atom.(RAO)
What is reduction? Reduction is the Gain of electrons by an atom.(OAR)
What is the oxidation number of Fe in FeSO4? +2(MUST have positive sign!!)
What are the common OAs? 1. MnO4-/H+ 2. Cr2O72-/H+ 3. NO3-(conc.) 4. NO3-(Dilute) 5. H2SO4(l) 6. Cl2(aq/g) 7. Br2(aq) 8. Fe3+
What are the common RAs? 1. Reactive metals: K, Na, Ca, Mg, Zn 2. Sulphite ions (SO32-) 3. SO2(g/aq) 4. Fe2+ 5. Iodide(I-)
What are the oxidising properties of nitric acid at diff. concentrations? Very dilute: no oxidising properties Dilute: forming NO, then NO turn itself into brown NO2 concentrated: directly form NO2
What are the colours of I2 in diff. solvent? Water: brown Organic solvent(eg:CCl4): purple
What is the possible problem of Zinc-Carbon dry cell? Zinc case will gradually become thinner and thinner, which may allow the acidic electrolyte NH4Cl to leak out.
What is the electron flow on a chemical cell? Anion loses electrons at anode. (AnOx) Cation gains electrons at the cathode. (RedCat)
What are the examples of exothermic reactions? 1. cracking 2. Thermal decomposition 3. Electrolysis (CDE)
What is the standard enthalpy change of neutralization? The standard enthalpy change of neutralization is the enthalpy change when 1 mole of water is formed from neutralization between an acid and a base under standard conditions.
What is the standard enthalpy change of formation? The standard enthalpy change of formation is the enthalpy change when 1 mole of substance is formed from its constitutuent elements in their standard states under standard conditions.
How to calculate enthalpy change of formation?
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