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3 pm, Jan 28 Jan 28, 2013

CBSE Board chemistry examination

As part of the IBNLive-Topper chat series, Kanika Rustagi, chemistry teacher, will interact with students who will appear for the 2013 CBSE Board examinations which start from March 1. Parents and teachers can also benefit from her tips.
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45 questions answered | 27 questions pending
  • Have done badly in preboard how do i improve? Asked by: Madhumita
  • Kanika Rustagi revise the chapters. It's always good to find out what kind of questions are going to be in the exam and the best way is too look through old exams. That will give you an idea of the layout of an exam, the number of short answers and long answers there will be and the amount of time you should be giving each section.
  • explain me sn1 and sn2 reaction in detail Asked by: shashank
  • Kanika Rustagi you can ask this in 'ask an expert' section on topperlearning.com
  • WHAT ACTTUALLY IS BENZENE Asked by: ansh
  • Kanika Rustagi benzene is an aromatic cyclic compound with formula C6H6
  • give a description about isomers?also define isomerism?give examples Asked by: prakhar maheshwari
  • Kanika Rustagi The existence of two or more compounds with same molecular formula but different properties (physical, chemical or both) is known as isomerism; and the compounds themselves are called isomers.
  • how would you name the following compounds 1. CH3-CH2-CH=CH2 2. CH3-CH2-CHO 3. CH3-(HCOH)-CH3 Asked by: Ishant
  • Kanika Rustagi 1. 1-butene 2. propanal 3. propanol
  • DIFFERENCE IN STRUCTURE OF DIAMOND AND GRAPHITE Asked by: ansh
  • Kanika Rustagi In diamond, each carbon atom is bonded to four other carbon atoms forming a rigid three-dimensional structure. In graphite, each carbon atom is bonded to three other carbon atoms in the same plane giving a hexagonal array.
  • Is any diagram important for chemistry S.A 2 portion ? Asked by: Saran
  • Kanika Rustagi Formation of micelles using diagram and cleaning action of soap using diagrams are important
  • define hydrogenation of vegetable oil? also give equation and its effects Asked by: prakhar maheshwari
  • Kanika Rustagi Unsaturated hydrocarbons add hydrogen in the presence of catalysts such as palladium or nickel to give saturated hydrocarbons. This reaction is commonly used in the hydrogenation of vegetable oils using a nickel catalyst.
  • I got low marks in preboard how do i improve before the final? Asked by: Madhumita
  • Kanika Rustagi practise more and more. revise all the chapters thoroughly
  • is that previous year question papers ouestion repeats sometime or not? Asked by: shashank
  • Kanika Rustagi yes, they can get repeated depending upon the quality of the question
  • explain about thomson's model of atom Asked by: pragya
  • Kanika Rustagi thomson model is plum pudding model and states that the electrons, in a sphere of positive charge, were like currants (dry fruits) in a spherical Christmas pudding.
  • WHAT ACTTUALLY IS BENZENE Asked by: ansh
  • Kanika Rustagi benzene is an aromatic cyclic compound with formula C6H6
  • MENTION THE CAUSES OF HARDNESS OF WATER Asked by: Ishant
  • Kanika Rustagi hardness of water is due to presence of bicarbonates, chlorides and sulphates of calcium and magnesium
  • 2008 board exam paper question will reapeat or not Asked by: shashank
  • Kanika Rustagi the good questions can be repeated but it is not mandatory that the questions will come from that paper
  • can smaal alkane molecules be polymerised and used as afuel? Asked by: akash
  • Kanika Rustagi Some of the smaller molecules formed by cracking are used as fuels, and some of them are used to make polymers in plastics manufacture.
  • Mam can you please give the composition of high speed petrol? Asked by: akash
  • Kanika Rustagi JP-4 is a kind of high speed petrol and is typically composed of about 50-60% gasoline and 40-50% kerosene, is highly volatile, and contains hydrocarbons in the C4-C16 range.
  • WHY DO SOAP FORM SCUM WITH HARD WATER Asked by: Ishant
  • Kanika Rustagi Scum is created when calcium ions (and or magnesium ions) present in hard water form an insoluble precipitate with soap. Soap consists of sodium salts of fatty acids.
  • What is potassium? Asked by: hira
  • Kanika Rustagi Potassium is an element with atomic no. 19 and symbol 19
  • how many elements do i learn for class 10? Asked by: prakhar maheshwari
  • Kanika Rustagi learn upto 30 elements atleast
  • what is the mole concept Asked by: mrinal
  • Kanika Rustagi Mole: a metric unit which is equal to 6.023 x 1023 particles Avogadro's number: 6.023 x 1023 Molar Mass: the mass in grams of 1 mole of a substance
  • What is Tautomerism? Asked by: vandna
  • Kanika Rustagi Tautomerism refers to the dynamic equilibrium between two compounds with same molecular formula. This reaction commonly results in the formal migration of a hydrogen atom or proton, accompanied by a switch of a single bond and adjacent double bond for example: keto-enol tautomerism
  • define catenation. why no other element exhibit the properties of catenation to the extent seen in carbon compounds Asked by: Ishant
  • Kanika Rustagi Catenation is the linkage of atoms of the same element into longer chains. Catenation occurs most readily in carbon, which forms covalent bonds with other carbon atoms to form longer chains and structures. Silicon also shows some catenation but due to weak bonds, the compounds formed are unstable. Carbon shows this property due to the formation of strong covalent bonds and its small size
  • explain important conversion of organic chemistry Asked by: shashank
  • Kanika Rustagi pleas specify the conversion
  • Crude oil is made up o which type of alkane molecules? Asked by: akash
  • Kanika Rustagi Crude oil is made up of large hydrocarbon alkane molecules
  • why do the bottom of cooking vessel get blacened Asked by: Ishant
  • Kanika Rustagi the bottom of cooking vessels get blackened because the air holes of the gas stove are getting blocked and incomplete burning of fuel is taking place producing a black smoke
  • Why are larger alkane molecules cracked to form smaller molecules to use it as a fuel? Asked by: akash
  • Kanika Rustagi Cracking is a process that turns large alkane molecules into smaller alkane and alkene molecules. An alkene molecule has a double bond, which makes it useful for making polymers. Fuels made from oil mixtures containing large hydrocarbon molecules are not efficient. They do not flow easily and are difficult to ignite. Crude oil often contains too many large hydrocarbon molecules and not enough small hydrocarbon molecules to meet demand - this is where cracking comes in.
  • who discovered cannal rays Asked by: pragya
  • Kanika Rustagi Eugen Goldstein
  • best and easy way to learn modern periodic table Asked by: Ishant
  • Kanika Rustagi Make a chart of the periodic table and place it in front of your bed; so that you are always seeing the table and this will help you in memorising the elements; try to learn the elements by learning them in a sequence i.e. by their group no. or period no. for example first learn the group 1 elements then 2nd and so on
  • WHICH BOOK TO BUY FOR SAMPLE PAPERS Asked by: ansh
  • Kanika Rustagi Refer to this link for good quality sample papers: http://www.topperlearning.com/student/sample_papers_board
  • MAIN MISTAKE THAT REDUCE CHEMISTRY MARKS IN 10TH PAPER Asked by: ansh
  • Kanika Rustagi Main mistake is in the balancing of the equations for the organic compounds etc. one should also try to write the correct IUPAC names for the compounds; for tips and tricks on exams, see the link below: http://www.topperlearning.com/student/tipsntricks_papers
  • WHY THERE IS A SPECIAL PLACE FOR HYDROGEN IN MODERN PERIODIC TABLE Asked by: ansh
  • Kanika Rustagi Hydrogen (H) is given a special place since it has only 1 electron and so exhibits some unique behavior. It has equal tendency to gain or lose its one electron to attain stable configuration. When it loses its one electron it behaves as alkali metals to form unipositive ion and when it gains one electron it behaves like halogens and forms negatively charged hydride ion.
  • How to remember p-block chemical reactions? Asked by: Shreshth bhardwaj
  • Kanika Rustagi try to memorize them by practising them and making notes or flashcards for them.
  • What happens when (D)-glucose is treated with the following reagents- a. HI b. Bromine water c. HNO Asked by: shashank
  • Kanika Rustagi when d-glucose is treated with HI, it gives n-hexane With bromine water, it gives gluconic acid by converting -CHO grouo to -COOH group. With HNO3, it gives glucaric acid or saccharic acid
  • HOW COAL AND PETROLEUM FORMED Asked by: ansh
  • Kanika Rustagi You can see the link below for understanding the formation of coal and petroleum: http://www.hk-phy.org/energy/power/source_phy/flash/formation_e.html
  • ONLY FIRST 20 ELEMENTS ARE REQUIRE TO LEARN IN MODERN PERIODIC TABLE IN CLASS 10 Asked by: ansh
  • Kanika Rustagi No, its not compulsory to learn only the first 20 elements;
  • what is the color of Cl2 Br2 I2 Asked by: manisha
  • Kanika Rustagi Cl2 has greenish yellow gas; Br2 is reddish brown and I2 is deep purple color.
  • WHAT QUESTION CAN BE ASKED ON PROPERTIES OF ETHANOL ,ETHANOIC ACID ETC IN 10TH EXAM Asked by: ansh
  • Kanika Rustagi questions like what happens when ethanoic acid is reacted with sodium hydrogen carbonate; what is the smell of ethanoic acid like; what happens when acetic acid is dissolved in 5 ml water etc.
  • How to revise organic chemistry ? Asked by: Shreshth bhardwaj
  • Kanika Rustagi organic chemistry can be revised by making flashcards or flowcharts for the important reactions and conversions; try to practice the reactions by once writing the products for the reactants and then by writing the reactants for the given products; practice the name reactions and make your concepts clear in the mechanisms shown by organic compounds like inductive effect etc.
  • HOW DO DO CHEMISTRY M C Q IN EXAM OF CLASS 10 Asked by: ansh
  • Kanika Rustagi clear up your concepts of the topics covered in the practicals for class X; mcqs are asked from them only; learn all the reactions and properties shown by ethanoic acid
  • Is it necessary to balance the reactions of iodoform test? Asked by: Nirnimesh Kumar Basak
  • Kanika Rustagi yes , reactions should always be balanced
  • 5 difference between ethanol and ethanoic acid Asked by: ansh
  • Kanika Rustagi 1. Ethanol is alcohol whereas ethanoic acid is a carboxylic acid. 2. The functional group in ethanol is -OH whereas in ethanoic acid, it is -COOH. 3. Ethanol has no effect on litmus solution i.e. it is neutral whereas ethanoic acid is acidic in nature and turns blue litmus red. 4. Ethanol does no react with sodium hydrogen carbonate whereas ethanoic acid reacts with it to evolve carbon dioxide gas. 5. Ethanol reacts with sodium to release hydrogen gas whereas ethanoic acid doesn't release hydrogen gas.
  • The IUPAc NAME IS Butanoic acid Asked by: Nirnimesh Kumar Basak
  • Kanika Rustagi Yes, it is the correct answer
  • What is the iupac name of CH3CH2CH2COOH Asked by: Sunita
  • Kanika Rustagi The IUPAC name is butanoic acid
  • what is isomerism Asked by: Sunita
  • Kanika Rustagi The existence of two or more compounds with same molecular formula but different properties (physical, chemical or both) is known as isomerism
  • What is the best way to memorize the formulas? Asked by: Nida
  • Kanika Rustagi Do lots of practice of the formulas; try to write the formulas as many times as possible or try flashcards, followed by a couple practice problems without looking up at the equations. Try to understand the equations in the formulas. Try to remember the units of the components in the formulas; like for example work has the unit = Nm since force has units: N and distance has units m so the formula for work is force x distance.

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Kanika Rustagi
Chemistry teacher