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POINTS TO REMEMBER IN CHEMISTRY by iron_man (Tony Stark)

23 pages, 13 questions, 13 questions with responses, 46 total responses,

Tanay Nayak
Avalon Heights International School, Mumbai

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Points to Remember in Chemistry Chapter1: Periodic Table Highest electronegative element Fluorine Highest electron affinity Chlorine Highest I.P Helium Ionisation potential Energy required Electron affinity Energy released 1. Do not identify the element unless and until specified. 2. Atomic size and Metallic character are the only two trends which increases down the group 3. While writing group number be very careful.. Its 1 or IA , 2 or 2A After 2 its becomes 13 or IIIA 4. While writing give reason based on Periodic table trends following points should be taken into consideration: Atomic size Nuclear charge / Attraction 5. Metals are REDUCING AGENTS (Alkali and alkali earth metals) 6. Non-metals are OXIDIZING AGENT ( Halogens) 7. Lanthanide: Period 6 8. Actinide: Period 7 ( Radioactive) 1 Chapter2: Chemical Bonding Definition to be studied: Electrovalent bond/ Electrovalency Covalent Bond/ Covalency Co-ordinate covalent bond Lone pair Compound Number of lone pair Water 2 Hydronium 1 Ammonia 1 Ammonium 0 Non- polar covalent compound Polar covalent compound Hydrogen, Oxygen, nitrogen, Water chlorine Metahne HCl Carbon tetra chloride Ammonia 1. While drawing diagram of co-ordinate covalent bond, do label the lone pair and co-ordinate covalent bond. 2. Ionic compound high electrostatic force of attraction- Reason for high M.P and B.P 3. Covalent compound have weak Vander waal s force of attraction-Reason for low M.P and B.P 4. Distinguish on page no 34 need to study without fail all the points. 2 Chapter 3A: Acid Bases and Salts Hydracids Hydrogen and non-metal Oxyacids Hydrogen, oxygen and non-metal Basicity of acetic acid and formic acid 1 (As it a weak acid it undergoes partial dissociation reactions producing less concentration of hydronium ion) pH Negative logarithm to the base 10 of hydrogen ion concentration expressed in moles/litre Insoluble sulphate salts Lead sulphate Silver sulpahate Calcium sulphate Barium sulphate Insoluble chloride salts Lead chloride (Only chloride which is soluble in hot water but insoluble in cold water) Silver chloride Mercury chloride Study table on page no 49 without fail. Molecular formula of all the salts on page no 49 Diagram based question page no 54 ( Ferric chloride) Definition and Examples of Deliquescent and efflorescent substances (Page 56) 3 Method for preparation of salts: Salt Method Sodium, potassium or ammonium salt Neutralization or titration Ferric chloride Direct synthesis Ferrous chloride Simple displacement / Action of acid on metal Lead salts Double decomposition/ Precipitation Acidic salt Decomposition by acid Copper salt Action of an acid on its oxide or carbonate Incase if question is asked on preparation of salts , first write down the method which you are 100% sure.. Strong Base/ Alkali Weak base Sodium hydroxide Ammonium hydroxide Potassium hydroxide Calcium hydroxide Magnesium hydroxide (All the metals except Na and K) Deliquescent Efflorescent Absorb moisture and change into Lose water of crystallization and turn liquid state into amorphous powder Hence they both are stored in closed container 4 1. In preparation of lead salts, if two marks question then two reaction, otherwise directly one step. Step one with dilute nitric acid Step two with soluble salts of like of sodium, potassium or ammonium 2. Remember all salts of sodium, potassium or ammonium are soluble 3. Hydrolyis, aqueous, solution : Simply add water and react And mention the colour change 4. Drying agent is FUSED calcium chloride 5. DO NOT USE CARBONIC ACID IN ANY REACTION Only alkalis are: 1. Sodium hydroxide 2. Potassium hydroxide 3. Ammonium hydroxide Strong acidic or alkaline solution contains only IONS Weak acidic and alkaline solution contains both unionized molecules and ions Ammonium hydroxide is WEAK ALKALI 5 Chapter 3 B: Analytical Chemistry Caustic soda: Sodium hydroxide Caustic potash: Potassium hydroxide 1. Do not just write white ppt: Mention gelatinous white ppt or chalky white ppt 2. Lead and zinc reacts with excess of sodium hydroxide 3. Copper and zinc reacts with excess of ammonium hydroxide 4. Reaction of aluminium with Caustic soda or caustic potash add water And alkali is hot conc. (Do not forget to mention that) 5. Amphoteric oxides or metals are : Zn, Al, Pb They react with both acid and base to give salt and water. 6. Aluminium in form of aluminum oxide or hydroxide DO NOT ADD WATER. 6 Chapter 4: Mole Concept Definitions to be studied: 1. Gay Lussac law 3. Mole 2. Avagadro s law 4. Avagadro s number 5. RMM (Molecular weight) 6. RAM ( Atomic weigt) REMEMBER WHILE WRITING LAW IT SHOULD BE IN ____ AND WORD TO WORD 1. How to identify difference between Gay Lussac and chemical reactions numerical Gay lussac all the compounds will be gases and no atomic weight will be given in bracket. Whereas in chemical reaction compounds will be in all state atomic weight ( Relative atomic weight) will be given in bracket. 2. Draw columns while solving numerical and use the words- gives, to produce etc.. 3. When volume is asked DO NOT FORGET TO MULTIPY 22.4 LITRES 4. Most importantly BALANCE THE GIVEN CHEMICAL REACTION. ( Do not get excited while solving the numerical) 5. Empirical formula: 2.5 Multiply by 2 all the three numbers Less than 2.5 make it 2 More than 2.5 Make it 3 6. WRITE FINAL ANSWER IN FORM OF STATEMENT ANDWRITE UNIT WITHOUT FAIL. 7 7. If number of atoms are asked DO NOT FORGET TO MULTIPLY with no of molecules For eg. If asked number of atoms in HNO3 Ans: 5 6.023 1023 No of oxygen atom in HNO3 Ans: 3 6.023 1023 No of oxygen atom in HNO3 Ans: 1 6.023 1023 No of molecule of nitric acid Ans: 6.023 1023 No of molecules for all the compounds will always be 6.023 1023 8. Read question very carefully. BE VERY ALERT WITH MOLE, MOLECUE AND ATOMS. 9. Avogadro s law is only applicable for Gases. 10. For vapour density sums: Incase given in bracket, lengthy sum. If not given in bracket, divide directly. Steps for Vapour density numerical: When given in bracket, Step 1: Find Volume You can take S.T. P as final ( P2, V2 and T2) in all numerical and given as initial ( P1, V1 and T1) . Step 2: Calculate the volume taking into consideration 1000 ml Step 3: Divide the above volume with 0.09 OR THE VALUCE GIVEN IN BRACKET 8 Step 4: If asked to calculate molecular weight: Multiply above answer by 2 (Practice sum no 1 on page no 86 based on vapour density) 11. Attempt empirical formula numerical after completing the entire paper. Note: Do not panic or get nervous seeing the numerical. Do not waste time on solving numerical. Do not spent more than 10 mins per numerical. 9 Chapter 5: Electrolysis Definition to be studied: 1. Electrolysis 2. Electroplating 3. Electro refining Practice diagram of electroplating and electrorefining given on page no 119 and 120 4. Study the following give reasons: Electrolytic cell made up of silica is used for the electrolysis of lead bromide. Electrode used in the process is made up of graphite. Molten lead bromide is used instead of solid lead bromide. Electrolysis of water is carried out on water acidified with dilute sulphuric acid. Dilute sulphuric acid is preferred instead of dilute nitric acid. Electrolysis of acidulated water is considered to be an example of catalysis. During electrolysis of copper sulphate using copper electrode the blue colour solution does not fade. During electrolysis of copper sulphate using platinum electrode the blue colour solution fades. A solution of ionic compounds is an electrolyte while covalent compound is a non-electrolyte. 10 1. Be careful with inert and active electrode. 2. For copper as active electrode WRITE BOTH THE OBSERVATION Decreases in mass Colour 3. Metal activity series need to learnt Anode Positively charged Oxidising electrode Left side Cathode Negatively charged Reducing electrode Right side 4. Electro plating Cathode: Object to be electroplated Anode: Active electrode 5. Electro refining Cathode: Pure thin sheet of copper Anode: Impure block of copper 6. Write the cathode and anode mentioned in text book do not write your own electrode. 7. Remember the entire metal activity series and the series of negative radicals given on page no 110 11 Chapter 6: Metallurgy Methods for extraction of metals: K Na Ca Electrolysis Mg Al Zn Fe Sn Reducing agent Pb Cu Hg Ag Thermal Decomposition Following things need to be studied: 1. Distinguish between metal and non-metal (All points) 2. Principle of Froth floatation, Magnetic separation and hydrolytic method 3. Give reason to be studied for extraction of aluminium Fused cryolite and Fluorspar is added to the electrolytic mixture of alumina. 12 A layer of powdered coke is sprinkled over the electrolytic mixture of alumina. Graphite anodes are continuously replaced during the electrolysis. NaOH is used to concentrate of bauxite (Impurities are ferric oxide and silica) Ans. As aluminium oxide is amphoteric in nature, so will react with both acid as well as salt to give salt and water, wheras the impurities ferric oxide and silica are no amphoteric in nature. 4. Function of cryolite and fluorspar individually. 5. ALUMINUM RENDERS passivity WITH CONC AS WELL AS DILUTE NITRIC ACID 6. Iron renders passivity only with con nitric acid. 7. All reaction of iron need to learnt well.. In exams they will not mention ferrous or ferric ( Be careful) Page 154 Most important.. 8. Molecular formula along with chemical name and common name need to be learnt for ores. 9. Con sulphuric acid : SO2 GAS 10. Dilute sulphuric acid : H2 11. Any question based on which metal gets displaced, answer is always based on metal activity series Copper carbonate is green in colour. 13 Chapter 7 A: Hydrochloric Acid Acid used in laboratory preparation of Concentrated Sulphuric acid HCl (non-volatile acid) Method used for collection of gas Upward displacement of air Drying agent Concentrated Sulphuric acid Formula of phosphorous oxychloride POCl3 Formula of meta phosphoric acid HPO3 Sublimable substance formed by NH4Cl reaction two gas i.e. ammonia and hydrogen chloride Reaction of con HCl with manganese Chlorine gas ( greenish yellow gas) dioxide Test for HCl 1. With ammonia- white dense fumes 2. With silver nitrate- Curdy white ppt 3. With MnO2 Greenish yellow gas Note: Only one reaction is with conc HCl in this chapter of hydrogen chloride, and the reaction is with manganese dioxide Sodium thiosulphate: Na2S2O3 (Four products) Study all the give reasons for lab preparation of HCl and diagram of special funnel arrangement 14 Chapter 7 B: Nitric Acid Concentrated nitric acid Nitrogen dioxide gas Dilute Nitric acid Nitrogen oxide ( Danger balancing) Cold , Very dilute nitric acid Hydrogen gas Heating of sodium and potassium Sodium and potassium nitrite (NO2) nitrate and oxygen gas (NO3) (Only nitrates which do not produce nitrogen gas) Heating lead and copper nitrate Lead and copper oxide + nitrogen dioxide Copper nitrate Copper oxide gas+ oxygen (Blue to black) Lead nitrate Lead oxide (White to Buff yellow) Heating silver and mercuric nitrate Silver and mercury + nitrogen dioxide gas+ oxygen Heating ammonium nitrate (Only ammonium nitrate leaves N2O + H2O no residue in the test tube) Test for nitric acid Thermal decomposition of conc nitric acid. Reaction of Cu with conc nitric acid Both these reactions gives reddish brown gas of nitrogen dioxide. 15 Brown ring FeSO4. NO (Nitroso Iron (II) Sulphate) Property of nitric acid It is an oxidizing agent If asked about the anion which Nitrate ion liberates reddish brown gas Nitrosyl chloride NOCl 1. Study all the give reasons for lab preparation of nitric acid 2. Renders passivity means: it forms thin oxide coating on the surface of the metal which prevents further reaction. Aluminum and iron renders passive. 3. Aquaregia reaction need to be learnt. (Page no 207) 4. Give reasons based on brown ring test (Page no 209) Freshly prepared acidified ferrous sulphate is used in brown ring experiment. Ans. Iron (II) sulphate on exposure to the atmosphere oxidizes to Iron (III) sulphate and the test will not answere with iron (III) sulpahte The brown ring decomposes on disturbing. Ans. When test tube is shaken the conc. H2SO4 may futher mix with water and heat evolved assists in decomposition of unstable brown ring. 16 Chapter 7 C: Ammonia Alkali used in laboratory preparation of Calcium hydroxide NH3 (Non- deliquescent) Method used for collection of gas Down ward displacement of air Drying agent Fused Calcium oxide ( Quick lime) ( Both are basic in nature; wont react with each other) Method used to collect ammonia in 1. Liquefaction ( Liquifies at -33 C at Haber s process 8atm pressure) 2. Dissolving in water Burning of ammonia Nitrogen gas Catalytic oxidation of ammonia Nitrogen oxide Ammonia Reducing agent 17 Ammonia with copper oxide Copper + Water + Nitrogen gas Black Brown Ammonia with lead oxide Lead + Water + Nitrogen gas Buff yellow Grayish Ammonia with excess of chlorine Nitrogen trichloride (Yellow coloured explosive liquid) + hydrogen chloride Neseler s Reagent Pale brown and on excess passage of (Potassium mercuric iodide) ammonia brown ppt is obtained Note: When alkali reacts with ammonium salt we always get ammonia as a gas Ammonium salt + Alkali Salt + Water + Ammonia Metal nitrides, do not forget to write warm water Liquid ammonia : Liq NH3 (Neutral in nature) Liquor ammonia: NH4OH (Alkaline in nature) AMMONIA IS REDUCING AGENT AMMONIA IS ALKALINE IN NATURE 18 Give reason: 1. Liq ammonia is used as refrigerant. Ans. (i) It is highly volatile (ii) Liquifies easily at -33 C 8 atm pressure 2. Ammonium hydroxide is used to remove grease stains. Ans. It can easily emulsify or dissolve fats, grease etc. Chapter 7 D: Sulphuric acid Catalyst used in the contact process Vanadium pentoxide (V2O5) Formula of oleum H2S2O7 Reaction with conc sulphuric acid SO2 is liberated Reaction of metals with dil sulphuric Hydrogen gas acid Reaction of carbonates and bi- Carbon dioxide gas carbonates with dil sulphuric acid Reaction of sulphite and bi-sulphites Sulphur dioxide with dil sulphuric acid Reaction of sulphides with dil Hydrogen sulphide sulphuric acid Potassium dichromate solution colour Orange to clear green 19 change on passing sulphur dioxide gas through it Note: 1. Use con sulphuric acid only for copper; incase asked to prepare copper sulphate all other metals will react with dil sulphuric acid. 2. Formula of sulphite is SO3 ( Eg. Sodium sulphite Na2SO3) 3. Sulphide is S ( Eg. Ferrous sulphide FeS) 4. Valency of bi-carbonte/ bi-sulphite is 1 5. Always use lead in form of lead oxide or hydroxide 6. Whenever reaction s between acid and base ; acid used is always dilute. Solve these types of questions: Some properties of sulphuric acid are given below. Choose the role played by sulphuric acid in each case. A: Dilute acid B: Oxidising agent C: Non-volatile acid D: Dehydrating agent. 1. CuO + H2SO4 CuSO4 + H2O 2. C6H12O6 6C + 6H2O 20 3. Fe + H2SO4 FeSO4 + H2 NaSO4 + H2O + SO2 4. Na2SO3 + H2SO4 5. Cu + 2H2SO4 6. NaNO3 + H2SO4 CuSO4 + 2H2O + SO2 NaNO3 + HNO3 Chapter 8: Organic Chemistry 1. Numbering is a must. (Do it with pencil) 2. Definition to be studies are : Catenation, Homologous series, Isomerism Catenation: The property by virtue of which a large no of atoms of the same element get linked together through covalent bonds to form straight and branched chains and rings of different size is called catenation. 3. Alkanes : Substitution reaction 4. Alkene and alkyne : Addition 5. Study electron dot structure of ethane, ethene and ethyne Single bond : 2 electron in the centre Double bond : 4 electron in the centre Triple bond : 6 electron in the centre 6. Reaction condition need to be written perfectly. 21 7. Be careful with alcoholic and aqueous KOH. 8. Reaction of alkanes with oxygen in presence of catalyst: Copper tube Alcohol ( No water is formed) MoO Aldehyde (Water is formed) 9. Anhydrous acetic acid on cooling below 16.5 C crystallizes out resembling in the pure form, forming a crystalline mass resembling ice. Hence pure acetic acid is called Glacial acetic acid. 11. IUPAC name Common name Ethene Ethylene Ethyne Acetylene Methanal Formaldehyde Ethanal Acetaldehyde Methanoic acid Formic acid Ethanoic acid Acetic acid (Vinegar) Give reasons: 1. 90% of all known compounds are organic in nature. Ans. Carbon is tetra valent and show the unique property of catenation and isomerism. Hence _____ 2. It is dangerous to burn methane in an in sufficient supply of air. Ans. As it will produce carbon monoxide gas which is highly poisonous. 22 Wish you all the very best. Do well. God bless you 23

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