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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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