LEARNINGCBSE

What is denoted by ln? Answer: ln is the symbol of natural log. Log is modern symbol. ln = 2.303 log

Sample paper General Instructions 1. All questions are compulsory. 2. Question nos. 1 to 8 are very short answer questions and carry 1 mark each. 3. Question nos. 9 to 18 are short answer questions and carry 2 marks each. 4. Question nos. 19 to 27 are also short answer questions and carry 3 marks each 5. Question nos. 28 to 30 are long answer questions and carry 5 marks each 6. Use log tables if necessary, use of calculators is not allowed. 1. Find out the number of atoms per unit cell in a fcc structure having only single     atoms at its lattice points .                                                                                                                                                                     2. State the condition resulting in reverse osmosis.                                                                                                         3. Express the rate of the following reaction in terms of disappearance of hydrogen in the reaction  

Question: A compound lens is made of two lenses in contact having powers +12.5 D and -2.5 D. An  object is placed at 15 cm from this compound lens.Find the position and nature of the image formed. Answer: P comp  = P 1   +P 2   = + 10 D F comp   = 100/10 cm 1/F =1/v - 1/u F = +10 cm, u = -15 cm, v = ?                                                                V= +30 cm  Image formed will be real inverted and enlarged.

Question: If a stone is thrown vertically upwards, its velocity continusously decreases. Why? Answer: If a stone is thrown vertically upwards, its velocity continusously decreases because it is thrown against gravity so gravitational force decreases its velocity by pulling it down.

Question: Atoms of element Y form   hcp   lattice and those of the element X occupy 2/3rd of tetrahedral voids. What is the formula of the compound formed by the elements X and Y? Answer: The number of tetrahedral voids formed is equal to twice the number of atoms of element Y and only 2/3rd of these are occupied by the atoms of element X. Hence the ratio of the number of atoms of X and Y is 2 × (2/3):1 or 4:3 and the formula of the compound is X 4 Y 3 .

Question :Classify following as amorphous or crystalline solids: Polyurethane, naphthalene, benzoic acid, Teflon, potassium nitrate, cellophane, polyvinyl chloride, fibre glass, copper. Answer:  Amorphous solids : Polyurethane, Teflon, cellophane, polyvinyl chloride, fibre glass . Crystalline solids   :  Naphthalene, benzoic acid, potassium nitrate,copper .

Physics LONG ANSWER QUESTIONS OF 5 MARKS EACH Q.1. Find expression for the force and torque on an electric dipole kept in a uniform electric field . Q.2. Find an expression for the maximum torque acting on an electric dipole when it is placed in a uniform electric field . Q.3. An electric dipole is held in a uniform electric field (i) using suitable diagram show that it does not undergo any translatory motion , and (ii) derive an expression for the  torque acting on it and specify its direction . Q.4.An electric dipole of dipole moment p is placed in a uniform electric field E . Write the expression for the torque τ experienced by the dipole . Identify the pairs of perpendicular vectors in the expression . Show diagrammatically the orientation of the dipole in the field for which the torque is (i) maximum (ii) half of the maximum value (iii) zero . Q.5. Find an expression for the work done in rotating an electric dipole in a uniform electric field . Q.6.Find an expression for

ELECTRO CHEMISTRY        Each question is of three marks.                                      . 1.(a)Define Faraday constant.How is it derived?                                                                                                (b)The resistance of a conductivity cell containing 0.001 M KCl solution at 298 K is 1500Ω.           What is the cell constant if conductivity of 0.001 M KCl  solution at 298 K is 0.146 X 10 -3   S/cm.  2.The standard electrode potential for Daniel cell is 1.1 V .Calculate the standard Gibb’s energy for      The reaction  Zn(s) +Cu 2+ (aq)  -------------  Zn 2+ (aq) +Cu(s)  3.Describe the preparation and electrode reactions of  fuell cell .                                                                  4.Explain Kohlrausch’s law of independent migration of ions.Write its one application.  5.How conductivity of an unknown solution be determined ?explain   6. If a current of 0.5 amp flows through a metallic wire for 3 hrs, then how many e

General Instructions 1. All questions are compulsory. 2. Question nos. 1 to 8 are very short answer questions and carry 1 mark each. 3. Question nos. 9 to 18 are short answer questions and carry 2 marks each. 4. Question nos. 19 to 27 are also short answer questions and carry 3 marks each 5. Question nos. 28 to 30 are long answer questions and carry 5 marks each 6. Use log tables if necessary, use of calculators is not allowed. 1. Give preparation reaction for Terylene.                                                                                                               2. What is chemical adsorption?                                                                                                                                3.Write the IUPAC name of [Pt(NH 3 ) 2 Cl(NO 2 )]                                                                                                          4.Write  an example of analgesic  and antipyretic drug .