Answers to Chemistry Revision
- Manganese IV oxide and hydrochloric acid.
- Hydrochloric acid and nitric acid.
- Normal salt-sodium sulphate. Acid salt-sodium hydrogen sulphate. The acid is sulphuric acid.
- Sodium hydrogen sulphate.
- Zinc amalgam.
- Ammoniacal silver nitrate.
- Red lead (Tri lead tetra-oxide).
- Nitrogen and hydrogen.
- Lead nitrate.
- Vandium pentoxide.
- Sodium hydroxide.
- Nitric oxide.
- Ammonium carbonate.
- Lead nitrate.
- Hydrogen and sulphur.
- In the solid state the ions are held together due to which the compounds are become bad conductors of electricity. In the molten or aq. solution state the ions gain kinetic energy and they break loose and move freely and hence they conduct electricity.
- Salts like calcium carbonate and lead carbonate are insoluble and they cannot be melted. They are solid in state and therefore cannot be electrolysed.
- When HCl is dissolved in water it forms a constant boiling mixture with b.p. 109.8°C and composition 22.2% by weight of HCL. Thus on boiling the liquid phase and the vapour phase composition remains the same and hence no concentration occurs.
- Hydrogen chloride is highly soluble therefore fumes come out when a bottle of HCl is opened. HCl fumes in moist air and forms mist of hydrochloric acid.
- Ammonia reacts with acids to form ammonium salts.
- Concentrated sulphuric acid is a hygroscopic substance that absorbs moisture when exposed to air. Hence it is kept in air tight bottles to prevent it from being diluted.
- Sulphuric acid leaves dark circles on the wooden plank because sulphuric acid react with cellulose of wood and cellulose it to charcoal.
- All bases are not alkalis because they are insoluble in water.
- Lead nitrate reacts with concentrated HCl to form insoluble PbSO4 which settles down at the bottom. Therefore it is not preferred for ring test.
- Ethyne is highly reactive than ethene due to the presence of triple bond between two carbon atoms.
- Barium chloride solution when added to sodium sulphate solution, a white precipitation of barium sulphate is formed but when barium chloride is added to sodium nitrate solution no visible reaction is seen.
- Pure water is a non-electrolyte, it has only molecules and no ions. Therefore a few drops of acid are added to it to convert it into an electrolyte.
- Bleaching action of sulphur dioxide is temporary because the bleached product on exposure to atmospheric oxygen adds on oxygen atoms and regains the original colour.
- Carbon tetrachloride is a pure covalent compound which is non polar whereas water is a polar solvent therefore carbon tetrachloride does not dissolve in water.
- In the manufacture of iron limestone is added to the furnace as limestone decomposes to give calcium oxide which acts as a flux and combines with impurities of silica to form fusible slag (calcium silicate).
- When silver nitrate reacts with dil. HCL a white precipitate of silver chloride is formed.
2. When hydrogen chloride mixes with ammonia a dense white fume of ammonia chloride is seen.
3. On addition of ammonia hydroxide to copper sulphate a blue precipitation is obtained. This precipitation dissolves in excess of ammonium hydroxide.
4. When concentrated nitric acid is added to reddish brown copper, the colour of the whole solution turns blue due to the formation of copper nitrate and a reddish brown gas, NO2 is also given out.
5. Barium chloride when added to dilute sulphuric acid forms a white precipitation of barium sulphate.
6. When a solution of calcium chloride is mixed with a solution of sodium carbonate a white precipitation of calcium carbonate is obtained.
7. On mixing of lead nitrate solution with sodium chloride solution a white precipitation if formed which is soluble in hot water.
8. When ethene is passed through a solution of bromine in tetra chloromethane then a reddish brown colour of bromine gets discharged.
9. When sodium hydroxide solution is added to zinc sulphate solution a white precipitation is obtained which dissolves in excess of sodium hydroxide.
10. Ammonia gas when bubbled through red litmus solution turns blue.
11. It turns yellow.
12. When sulphur dioxide is passed through lime water, the lime water turns milky, milkiness disappears.
- Deliquescence is the property by which a substance absorbs water from the atmosphere and forms a solution.
- When a class of organic compounds is arranged in ascending order of its molecular weight, it constitutes a homologous series. The homologous series of alcohol is written as:
3. Electron affinity is the amount of energy released when an electron is added to an isolated gaseous atom and is converted into a negative ion.
4. Atomic radius is the distance from the centre of the nucleus to the outermost shell of electrons.
5. Isomerism is a phenomenon where organic compounds exhibit same molecular formula but different structural formula.
6. Functional group is an atom or group of atoms responsible for particular chemical behavior of organic compounds.
7. An alloy is a substance formed by adding other metals to a basic metal so as to obtain certain desirable properties.
8. An ore is the mineral from which metals can be extracted easily and profitably.
9. Weak acid is an acid that dissociates only partially in aqueous solution thereby producing a low concentration of hydrogen ions.
10. The salts formed by partial displacement of hydrogen ions of an acid molecule by a basic radical are said to be Acid salts.
- Ethene dicolourises bromine water but ethane does not.
- Electrolytes are chemical compounds which conduct electricity in fused or in aqueous solution state, whereas non-electrolytes are chemical compounds which do not conduct electricity either fused or in aqueous solution state.
- Voltmeter is an instrument used to measure potential difference while voltameter is a vessel in which electrolysis is carried out.
- Oxidation is a chemical change which involves the removal of electrons, or addition of oxygen or an electronegative atom or ion or removal of hydrogen or an electropositive atom or ion from a substance whereas reduction is a chemical change which involves addition of hydrogen or an electropositive atom or ion, or removal of oxygen or an electronegative atom or ion from a substance.
- Electrovalent bonding takes place by transfer of valence electrons from one atom (generally metallic) to another (generally non-metallic). Covalent bonding rakes place by sharing of pairs of electrons between two reacting atoms.
- Ionization potential is the amount of energy required to remove a loosely bound electron from outermost shell of an isolated gaseous atom whereas electron affinity is the amount of energy released when an atom in the gaseous state accepts an electron to form an anian.
- Roasting is a process of heating a sulphide ore in the presence of excess air to a high temperature to convert it into corresponding oxide or sulphate. Rusting is a slow oxidation of iron by oxygen of the air in the presence of moisture.
- Aqueous solution of HCl is acidic as it contains hydronium ion whereas aqueous solution of Ammonia is alkaline as it contains hydroxyl ions.
- The basicity of an acid is the number of hydrogen ions which can be produced per molecule of the acid in aqueous solution whereas the acidity of bases is the number of hydroxyl ions which can be produced per molecule of the bases in aqueous solution.
- Catenation is the tendency of an element to form chains of identical atoms whereas isomerism is the phenomenon where organic compounds exhibit same molecular formula but different structural formula.