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VIBGYOR High First Term Examination 2017-2018 CHEMISTRY Grade: VIII Max. Marks: 80 Date: 26/09/17 Time Allowed: 2 hours INSTRUCTIONS: Answers to this paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the question paper. The time given at the head of this paper is the time allowed for writing the answers. The intended marks for the questions or parts of questions are given alongside the questions. ______________________________________________________________________ Part I (40 Marks) Attempt all questions from this Part Question 1 A. Complete the following: [1x5=5] a. The energy required to change water from the solid to its liquid state at its melting point without any change in temperature is called_______. b. The reaction in which more active element displaces a less active element from its salt solution is known as_______ reaction. c. Iron metal reacts in moist air by oxidation for a long period to give __________. d. Metalloid present in the period 3 ____________. e. A solution in which more of solute can be dissolved at a given temperature is said to be ___________ solution. Page 1 of 7 B. Answer the following questions: i. [5] Hydrogen is collected by downward displacement of water and not of air, even though it is lighter than air. ii. A candle brought near the mouth of a jar containing Hydrogen gas starts burning but is extinguished when pushed inside the jar. iii. Iron will liberate hydrogen from dilute H2SO4 but silver cannot. iv. Oxy-hydrogen flame is used for welding and cutting metals. v. Apparatus for laboratory preparation of hydrogen should be air tight and away from a naked flame. C. Choose the correct answer: [1x10=10] 1. Group 17 elements are also called as a. Alkali metal b. Alkaline earth metal c. Halogens d. Chalcogens 2. Sodium sulphate decahydrate is called as a. Green vitriol b. Gypsum c. Epsom salt d. Glauber s salt 3. The metal which catches fire and burns with a lilac-colored flame a. Potassium b. Sodium c. Calcium d. Aluminum 4. The valency of nitrogen in dinitrogen pent oxide (N2O5) is a. Two b. Five c. Three d. Four 5. Which of these elements are Alkaline earth metal a. O b. H c. Ca d. Ar Page 2 of 7 6. The number of Sulphur atoms in bisulphite Radical is a. Two b. Three c. Zero d. One 7. Which of the following is the correct electronic configuration of Chlorine a. 8,2,9 b. 2,8,7 c. 2,8,8,1 d. 1,2,8,8 8. The formula of Sodium Carbonate is Na2CO3 and that of Calcium bicarbonate is a. CaHCO3 b. Ca(HCO3)2 c. Ca2HCO3 d. Ca(HCO3)3 9. A metal that doesn t react with dilute hydrochloric acid and dilute sulphuric acid. a. Ca b. Mg c. Cu d. Al 10. Metals above carbon can usually be extracted by a. carbon or carbon monoxide reduction b. thermal decomposition c. Electrolysis d. Synthesis D. State your observation :(no need to write chemical reaction) a. Copper sulphate crystals are heated. b. Pure aluminum is exposed to air. c. Silver nitrate is treated with sodium chloride. d. Heating of Lead nitrate. e. Zinc reacts with steam. Page 3 of 7 [1x5=5] E. Match the following: [1x5=5] Column A Column B 1) Atomic No. 7 and Mass no.14 a) -3 2) Electronic Configuration 2, 8 b) -1 3) Neutrons 14, Electrons 13 c) +2 4) Neutrons 20, Protons 20 d) - 3 5) Electronic Configuration 2, 8, 7 e) 0 F. Write the balanced chemical equations for each of the following i. ii. [1x5=5] Iron reacts with steam to produce tri ferric tetra oxide and hydrogen. Barium chloride reacts with Sulphuric acid to yield Barium sulphate and hydrogen. Sodium reacts with water to yield sodium hydroxide and hydrogen Glucose reacts with conc. sulphuric acid to yield carbon and water. Carbon dioxide dissolved in water reacts with lime stone to yield calcium bicarbonate iii. iv. v. G. A small piece of calcium metal is put into a trough containing water. There is effervescence and white turbidity is formed. i. ii. iii. iv. [5] Name the gas formed in the reaction. How would you test the gas? Write an equation for the reaction. What would you observe when a few drops red litmus solution are added to the turbid solution. What would happen if dilute hydrochloric acid is added to the turbid solution. Write the equation for the reaction. Section II (40 Marks) v. (Attempt any four questions from this section) Question 2 A. Identify the type of reaction: [1x5=5] i. Zn + CuSO4 ZnSO4+ Cu ii. 2H2 + O2 2H2O iii. 2Zn(NO3)2 2ZnO + 4NO2 + O2 iv. 2KI +H2O2 2KOH + I2 v. H2S + Cl2 2HCl + S Page 4 of 7 B. Answer in short: i. [1x5=5] What happens to the atomic size of elements on moving from left to right in a period and why? ii. What is periodicity? iii. How many periods and groups are there in long form of periodic table? iv. State Mendeleev s periodic law. v. Mention two drawbacks which are unsolved in the Mendeleev s periodic classification. Question 3 A. (i) Draw the neat and labelled atomic structure of the Phosphorus. [2] B. (i) Normally, solubility of crystalline solid increases with temperature. But it does not increase uniformly in all substances. (a)Name a substance whose solubility increases rapidly with temperature. (b) Name a substance whose solubility decreases with rise in temperature. (c) Write any one use of solubility curve. C. Write balanced chemical equations: i. Aluminium treated with steam ii. Lead nitrate reacts with hydrogen sulphide. iii. Water gas reacts with steam. iv. Copper oxide reacts with hydrogen. v. Hot coke (carbon) reacts with steam. [3] [1x5=5] Question 4 A. Give reasons for the following: [2x3=6] i. Sodium is kept in inert solvent. ii. The chemical properties of isotopes are same. iii. Iron displaces copper from an aqueous solution of copper sulphate. B. Differentiate between the following pairs: i. Neutralisation and precipitation reaction ii. Oxidation and Reduction Page 5 of 7 [2x2=4] Question 5 A. Electronic configuration of element T is 2,8, 7. [1x5=5] i. What is the group number of element T? ii. What is the Period number of element T? iii. How many valence electrons are there in an atom of T? iv. What is the valency of element T? v. Is the element T a metal or a non-metal? B. Name the following: i. ii. iii. iv. v. Question 6 [5] Formula of Copper (II) carbonate. An element with a variable valency of 2 and 4. The bond formed due to complete transfer of electrons from one atom to another. An atom or group of nonmetallic atoms that react as a single unit. The binding force present between two or more atoms in a molecule. A. Give balanced chemical equation: [5] i. Zinc sulphide reacts with oxygen to yield zinc oxide and Sulphur dioxide. ii. Nitrogen reacts with hydrogen to form ammonia. iii. Manganese dioxide mixed with hydrochloric acid to form Manganese chloride, water and chlorine. iv. Ferric oxide when treated with carbon monoxide it yields iron and Carbon dioxide. v. Sodium carbonate is treated with dil. H2SO4 B. Complete the following table where [5] i. A, B, C and D are elements, given that B is an inert or noble gas just below helium: ii. Which one of the elements A, B, C and D would you expect to be: (i) Metallic (ii) Non metallic Element Atomic Number No. of Electrons No. of Electrons in Outermost shell A Z 1 i. ____ v. ____ B Z ii. ____ vi. ____ C Z+1 iii. ____ vii. ____ D Z+4 iv. ____ viii. ____ Page 6 of 7 Question 7 A. [4] i. Observe the following diagram and answer the following questions. a. What were the postulates from this observation of an atomic model? b. State two drawbacks of this model. B. Define the following terms: i. Modern periodic law ii. Hygroscopic iii. saturated solution iv. Octet rule v. Efflorescent vi. Penultimate shell [6] Page 7 of 7
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