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ISC Class Board Exam 2021 : Chemistry

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Nisha Boweri
Andhra University (AU), Visakhapatnam
Mech engg

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ALWARDAS PUBLIC SCHOOL VISAKHAPATNAM HALF YEARLY EXAMINATION 2020 CHEMISTRY PAPER-I (THEORY) Question Paper Internal Assessment Total CLASS: XI (TIME ALLOWED: THREE HOURS) Date:05.11 .19 ( Candidates are allowed additional 15 minutes for only reading the paper.) They must not start writing during this time. ---------------------------------------------------------------------------------------------------------------All questions are compulsory Question 1 is of 20 marks having four sub parts, all of which are compulsory. Question numbers 2 to 8 carry 2 marks each, with any two questions having internal choice. Question numbers 9 to15 carry 3 marks each, with any two questions having internal choice. Question numbers 16 to 18 carry 5 marks each, with an internal choice. All working, including rough work, should be done on the same sheet as, and adjacent to the rest of the answer. The intended marks for questions or parts of questions are given in brackets [ ]. Balanced equations must be given wherever possible and diagrams where they are helpful. When solving numerical problems all essential working must be shown. In working out problems use the following data: Gas constant R=1.987 cal deg -1 mol -1 = 8.314 Jk-1 mol-1 = 0.0821 dm3 atm k-1mol-1 1 l atm= 1 dm3 atm=101.3J1 Faraday=96500 coulombs. Avogadro s no=6.023x1023 ----------------------------------------------------------------------------------------------------------------Question 1 a) Fill in the blanks by choosing the appropriate word/ words from those given in the brackets: [4] ( covalency, orbital,sub shells, electrovalency, shell, cation, , anion, +2, -2 ) i)--------------- is the number of electrons lost or gained by an element to form an ion. ii) Magnetic quantum number is used to represent ------------- of which a given subshell is composed. iii)--------------- is bigger in size than its parent atom. iv)The oxidation state of group 2 element is-------------. b) Complete the following statements by selecting the correct alternatives from the choices given: [4] i) Bromine belongs to group ---------------------1) group 14 2) 15 3) 16 4) 17 /70 /30 /100 ii) Oxidation is defined as: 1) Loss of electrons 2) loss of protons 3) loss of neutrons 4) gain of electrons iii) Metallic character of the elements ---------- on moving from top to bottom in a group. 1) decreases 2) increases 3) remains same 4) no change iv) Elements having their two outer most shells incomplete. 1) noble gases 2) s- block 3) p-block 4) d-block . c) Match the following: A i) molarity ii) normality iii) metals iv) non metals d) [4] B gram equivalents per litre of the solution oxidizing agent reducing agent no. of moles of solute per litre of solution Answer the following questions: [8] i) What is the maximum number of electrons that can be accommodated in the subshell represented by following set of quantum numbers. a) n-2, l-1 b) n-5, l-3 ii) Define Electronegativity and molality. iii) Write the electronic configuration of Chromium [Z- 24].What is the reason for abnormal electronic configuration of Chromium ? iv) What happens to valence electrons in a group and in a period? PART-II Question 2 a) State : i) Law of definite proportions. ii) Law of reciprocal proportions . OR b) State i) Gay Lussac s law of gaseous volumes. ii) Law of conservation of mass. Question 3 Write any two differences between sigma bond and pi bond . [2] Question 4. Why is copper more stable? Write its electronic configuration [2] [2] Question 5 [2] How many shells, orbitals, electrons and valence electrons are there in an atom having atomic weight 27 and atomic number 13 ? Question 6 [2] Give a suitable reason for the following. i) Atomic radii increases down the group 13. ii) Ionisation energy increases across the period. Question 7 a) State i) Aufbau s principle ii) Hund s rule of maximum multiplicity. OR [2] b) State i) Pauli s exclusion principle ii) State Heisenberg s uncertainty principle. Question 8 a) Name the alkaline earth metal which shows diagonal relationship with aluminium. b) What is the number of unpaired electrons in Mn 2+ ion? ( at.no. Mn=25) Question 9 Find the oxidation number of the following : i) S in Na2S4 O6 ii) Cr in K2Cr2O7 iii) S in HSO4OR Find the oxidation number of the following : i) S in Na2S3O3 ii) Mn in KMnO4 [2] [3] iii) Pt in (PtCl6) 2Question 10 An atom has 2K, 8L and 5M electrons. Find the total number of : i) protons ii) principal quantum number iii) p electrons iv) paired electrons v) unpaired electrons vi) valency. [3] Question 11 [3] A sugar syrup of weight 214.2g contains 34.2 g of sugar (C12H22O11). Calculate mole fraction of sugar in the syrup. (C-12, H-1, O-16) Question 12 Complete and balance the following equations: i) Na2S2O3 + H2SO4 ----------- ii) Na2S2O3 + AgNO3 ----------- iii) Na2S2O3 + I2 ----------- [3] Question 13 a) What is the maximum number of electrons that can be accommodated in the [3] subshell represented by following set of quantum number : i) n=2, l=1 ii) n=5, l=3 iii) n=3, l=2 i) n=2, l=0 OR ii)n= 3, l=1 iii) n=4, l=2 Question 14 Write a balanced chemical equation for the preparation of the following: i) Sodium thiosulphate from sodium sulphite ii) Calcium hydroxide from calcium oxide iii) Sodium carbonate by solvay s process. [3] Question 15 i) The equivalent weight of H2SO4 is .. ii) The equivalent weight of the element aluminium is .. iii) The equivalent weight of calcium hydroxide is .. ( Atomic mass H-1, S-32, O-16, Al-27, Ca-40) [3] Question 16 a) Write the electronic configuration of the following elements/ion : i) Fe 2+ ii) Argon iii) Sodium iv) Iodine (Z=53) v) Zinc OR b) Write the electronic configuration of the following elements/ion : i) silicon ii) Calcium iv) Barium ( Z = 56) [5] iii) Cu+ v) O2-. Question 17 a) Draw the Lewis structure or electron dot structure of the following: i) Na2S ii) O2 molecule iii) MgO iv) NH3 v) C2H2 OR b) Draw the Lewis structure or electron dot structure of the following: i) MgF2 ii) N2 molecule iii) NaCl iv) CO2 v) C2H4 [5] Question 18 a) 4g of NaOH are dissolved in 200 ml of water. Find the molarity of the (Na-23, O-16,H-1) b) Calculate the normality of a solution containing 150 g of Mg(OH) 2 in one litre of solution. OR c) [5] Complete and balance the following chemical equations: i) Al + NaOH + H2O ------------------ ii) Al + conc. H2SO4 ------------------ iii) SiO2 + C ------------------ iv) CaCO3 ----------- v) Na2B4O7 + HCl ----------- --------------------------------------------------------

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