ibnlive » Chat

3 pm Feb 11, 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.
39 questions answered
  • what is syllabus for board exam? is it entire syllabus or syllabus covered in last term? Asked by: bhaz
  • Kanika Rustagi For class X: its only SAII term's syllabus while for class XII: Its the entire syllabus
  • Hello Madam, Just want to know whether Chemistry is a tougher thing in CBSE as compared to ICSE and state boards? Asked by: sandeep
  • Kanika Rustagi Nothing is tough; just focus on your studies and be confident about your preparations. Morever, the state boards and ICSE all follow the same pattern and syllabus. The difference is just in the type of questions asked
  • Ma'am I am a student of XI and want to ask about chapters on Inorganic chem...In them what type of questions are really expected to come..??? as I'll be giving DAV board... Asked by: Disha Kapila
  • Kanika Rustagi Application based questions, questions on the structures of the compounds formed by the group elements like that of P or S are asked. Questions on the properties shown by the group/ period elements are also asked. Learn the reactions and properties shown by the s-block and p-block elements. Questions are very often asked from these.
  • the number of possible conformations for a single bond are---- and how? Asked by: vandna
  • Kanika Rustagi Single bonds in organic molecules are free to rotate, with the result that organic molecules can adopt a huge number of possible conformations.
  • what is order of energy of eclipsed and staggered conformations for ethne moleule and why? Asked by: vandna
  • Kanika Rustagi The lowest energy conformation of ethane is the staggered conformation, in which all of the C-H bonds on the front carbon are positioned at dihedral angles of 60°relative to the C-H bonds on the back carbon. In this conformation, the distance between the bonds (and the electrons in them) is maximized. Ethane molecule has highest energy in eclipsed conformation, where the hydrogens on the front carbon are as close as possible to the hydrogens on the back carbon.The energy of the eclipsed conformation is approximately 3 kcal/mol higher than that of the staggered conformation. Eclipsed is the highest energy conformation because of unfavorable interactions between the electrons in the front and back C-H bonds.
  • Thank a lot for ur help ma'am....please tell me about the chapter Hydrogen also..?? Asked by: Disha Kapila
  • Kanika Rustagi Questions on properties and uses of hydrogen; Classification of hydrides as ionic, covalent and interstitial; Structure, preparation, reactions and uses of hydrogen peroxide; chemical properties of water and heavy water can be asked.
  • what is saytzeff rule? Asked by: vandna
  • Kanika Rustagi Saytzeff Rule states that base-induced eliminations (E2) will lead predominantly to the olefin in which the double bond is more highly substituted i.e. major product is the most substituted alkene.
  • Why rutherford take gold foil for his experiment? Asked by: Aman Gupta
  • Kanika Rustagi Gold is highly malleable; gold leaf can be made in thicknesses around 100 nm or 4 micro-inch. It was the best material for the job.
  • ma'am i want to ask how to balance an equation Asked by: atiksha
  • Kanika Rustagi 1. Write down your given equation. 2. Write down the number of atoms that you have on each side of the equation. Look at the subscripts next to each atom to find the number of atoms in the equation. 3. Add coefficients to the atoms on the right/left of the equation to balance it with the atoms on the left/right of the equation. The first step in balancing a chemical equation is to write the number of atoms of each element present on the left hand side and right hand side. We should always start balancing with the compound that contains maximum number of atoms. It can be reactant or a product. Then in that compound select the element which has the maximum number of atoms. While balancing a chemical equation, the molecular formulae of the reactants and products should not change. The molecular formulae are simply multiplied by suitable coefficients.
  • ThankS ma'am....then WHAT about he number of possible conformations for a double and triple bonds are Asked by: vandna
  • Kanika Rustagi For any alkene with two different groups around the double bonded carbon atom, interchanging the two groups at either carbon of the double bond gives different molecules hence stereoisomers
  • i am a student of class viii and want to ask how to balance an equation ? Asked by: atiksha
  • Kanika Rustagi Already answered
  • Mam, What is benzeen?? Asked by: Sarang lehra
  • Kanika Rustagi Benzene is C6H6; its an aromatic compound
  • what is mole? Asked by: keerthana
  • Kanika Rustagi mole is the amount of substance that contains the same number of particles (atoms/ ions/ molecules/ formula units etc.) as there are atoms in exactly 12 g of carbon-12
  • is it important to learn the whole Periodic table for 9th class SA2 examination?? Asked by: Sarang lehra
  • Kanika Rustagi No, its not compulsory to learn the whole periodic table but try to learn at least the first 30 elements so that you are able to analyze questions asked on patterns followed in a group or period
  • can you pls explain me wat is mole. Asked by: keerthana
  • Kanika Rustagi The mole is the amount of substance that contains the same number of particles (atoms/ ions/ molecules/ formula units etc.) as there are atoms in exactly 12 g of carbon-12. 1 mole of any substance = 6.022 x 1023units
  • Hello!I am a student of class ix. My question is- The atomic number of an element is 11 and mass number is 23.What will be the number of electrons,protons and neutrons? Asked by: Sahiti
  • Kanika Rustagi No. of electrons (Z) = 11 No. of protons = 11 No. of neutrons = A - Z = 23 - 11 = 12
  • what is E2 mechanism in common language? Asked by: vandna
  • Kanika Rustagi The term E2 stands for "elimination bimolecular". E2 is a one-step process of elimination with a single transition state. In the E2 mechanism, a base abstracts a proton neighboring the leaving group, forcing the electrons down to make a double bond, and, in so doing, forcing off the leaving group. A strong base is required for the reaction to occur
  • the ratio of excluded volume and actual volume of a real gas is-------- Asked by: vandna
  • Kanika Rustagi Excluded volume or corrected volume = volume a molecule occupies without touching another molecule. It is four times the actual volume
  • what is molarmass Asked by: fahmida
  • Kanika Rustagi Molar mass = Mass of one mole of any substance = Gram atomic mass or gram molecular mass or gram formula mass of the substance
  • What is an aromatic compound?? Asked by: Sarang lehra
  • Kanika Rustagi In these compounds, six carbon atoms combine with alternate single and double bonds and form a hexagonal ring also called the benzene ring.
  • what is surface tension?? What is doppler effect?? How to find cos theta?? Asked by: gnaras
  • Kanika Rustagi Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. Doppler effect is the apparent change in the frequency of the wave due to relative motion of the source and observer. It can be observed both in light and sound waves. Please ask one question at a time.
  • how to learn mole in an easier way Asked by: fahmida
  • Kanika Rustagi Mole concept is very simple. Just be clear with the definitions of the terms like mole, molar mass. Mole is the amount of substance that contains the same number of particles (atoms/ ions/ molecules/ formula units etc.) as there are atoms in exactly 12 g of carbon-12. So, if you are asked to find the number of moles in any compound then, Number of moles = Given number of particles/Avogadro’s number or = given mass/ molar mass of substance For ex: If 46 g of Na is given and you have to find the no. of moles, then n= 46/23 = 2 moles
  • which are the ninteenth and twentith elements Asked by: fahmida
  • Kanika Rustagi Potassium: Atomic no. 19 Calcium: Atomic no. 20
  • while doing nomenclature when it gets compulsory to number the chain? i am confused? plz tell Asked by: shrawani
  • Kanika Rustagi While doing the nomenclature: a. Select the parent carbon chain: i. Select the longest carbon chain as the parent chain. ii. If a double or a triple bond is present in the carbon chain, it should be included in the parent chain. b. Number the parent carbon chain from that carbon end such that the double bond, triple bond or side chain gets the lowest number.
  • is it necessary to mug up the entire lab method for production of ethanol and ethanoic acid?? Asked by: shrawani
  • Kanika Rustagi No, you don't have to mug up anything; just understand the mechanism behind the reaction and learn the reactants and conditions required that's it.
  • can u plz explain me why the third period has 8 elements?? Asked by: shrawani
  • Kanika Rustagi According to the (n + l) ,the 3d orbital is higher in energy in than the 4s orbital. As a result, they are filled after the 4s orbital. Thus in the elements belonging to the third period, only 3s and 3p orbitals are available for filling, and hence the number of elements in the third period are 8.
  • hello Ma'm, how can i prepare best for chemistry exam in 4-5 days though i have not learn't anything yet ? Asked by: Prashant Malik
  • Kanika Rustagi there are no shortcuts for anything in life; first of all start with the chapters or concepts you are weak in so that you can spend a quality time in understanding them and practice previous year papers and you can log on to topperlearning.com for more exam tips and sample papers
  • the ratio of the rate of diffusion of helium and methane under identical condition of pressure and temp. is Asked by: vandna
  • Kanika Rustagi ratio of He/CH4 = Sq root(Mass of CH4/mass of He) = Sq root(16/4) = 2:1
  • i have aquestion how to tackle the exam fear Asked by: fahmida
  • Kanika Rustagi Be relaxed, revise your syllabus to gain confidence and try to practice as many papers as you can so that you become confident enough that you are ready for exams. Log on to topperlearning.com for practicing sample papers.
  • what is the difference between "nitrogen" and "nitrogen gas" Asked by: Sumesh
  • Kanika Rustagi Nitrogen, N is an element with atomic mass 14 whereas Nitrogen gas, N2 is a molecule formed by two N atoms and has molecular mass 28.
  • What are alpha particles??are they atoms?? If they r not atoms how the exists independently as we had read that the subatomic particles cant exist independently. Asked by: Sarang lehra
  • Kanika Rustagi Alpha particles (named after and denoted by the first letter in the Greek alphabet, α) consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. Alpha particles are released during alpha decay processes which can happen most especially to ultra-heavy nuclei like uranium. Alpha particles (symbol α ) are a type of ionizing radiation ejected by the nuclei of some unstable atoms.
  • can u explain about the water cycle? Asked by: vs asfiya
  • Kanika Rustagi The water cycle, also known as the hydrologic cycle or the H2O cycle, describes the continuous movement of water on, above and below the surface of the Earth. It is the journey water takes as it circulates from the land to the sky and back again. The Sun's heat provides energy to evaporate water from the Earth's surface (oceans, lakes, etc.). Plants also lose water to the air (this is called transpiration). The water vapor eventually condenses, forming tiny droplets in clouds. When the clouds meet cool air over land, precipitation (rain, sleet, or snow) is triggered, and water returns to the land (or sea). Some of the precipitation soaks into the ground. Some of the underground water is trapped between rock or clay layers; this is called groundwater.
  • Mam,I am class ix student. How to learn atomic numbers of elements? and how to read periodic table in easiest way? Asked by: Sahiti
  • Kanika Rustagi There are no shortcuts for these. You have to learn the atomic numbers for the elements; its just that it will take some time to memorise all in one go but after 2-3 times, you'll become confident in these.
  • the ratio of the rate of diffusion of a given element to that of helium is 1:4. what is The molecular weight of element Asked by: vandna
  • Kanika Rustagi Molecular weight will be 64
  • how to find nodal planes in Px orbital is Asked by: vandna
  • Kanika Rustagi In a p orbital, there is a nodal plane, where the electron has zero probability of being found ever; on both sides of the nodal plane, there is a nonzero probability of finding the electron. Px has yz nodal plane.
  • helooo maam i am a girl 9 how can i attend the chemistry test with full concentration and confidence Asked by: fahmida
  • Kanika Rustagi You can attend the test with full confidence only when you have prepared well for the test. Just revise all the chapters, then you'll automatically feel confident and will be able to answer well in the test.
  • What are applications of Isobars??IN book the applications of isotopes are given but What about isobars?? Asked by: Sarang lehra
  • Kanika Rustagi They don't have much applications
  • total number of hybrid orbitals on central iodine in tri-iodide ion(I3-) are Asked by: vandna
  • Kanika Rustagi AX2E3, linear. The central iodine is dsp3 hybridized
  • Maam i have a question, why are ceramics more capable of holding tension compared to metals? Asked by: @P
  • Kanika Rustagi Ceramics are compounds between metallic and non-metallic elements. The atomic bonds are usually ionic, where one atom, (non-metal), holds the electrons from another, (metal). The non-metal is then negatively charged and the metal positively charged. The opposite charge causes them to be bond together electrically. Sometimes the forces are partially covalent. Covalent bonding means the electrons are shared by both atoms, in this case electrical forces between the two atoms still result from the difference in charge, holding them together. This is what gives ceramics their properties such as strength and low flexibility. Hence, ceramics are more capable of holding tension compared to metals

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Kanika Rustagi
Chemistry teacher