MC 17 C - 6 SECTION - I

Transcription

1 SECTION - I (40 marks) Compulsory : Attempt all questions from this section. Question 1. (a) Name the gas in each of the following : An alkaline gas which gives dense white fumes with hydrogen chloride. The gas produced on reaction of dilute sulphuric acid with a metallic sulphide. A gas which turns acidified potassium dichromate clear green. The gas evolved on reaction of aluminium with boiling concentrated caustic alkali solution. State your observation /observations in each case : Sodium hydroxide solution is added to ferrous sulphate solution at first a little and then in excess. Oil of vitriol is added to blue vitriol. Ammonia gas is burnt in an atmosphere of oxygen in the absence of a catalyst. Excess ammonium hydroxide solution is added to lead nitrate solution. Choose the correct answer from the options given below. Write down only the letter corresponding to the correct answer : The metal oxide which can react with acid as well as alkali is : (A) Silver oxide (B) Copper (II) oxide (C) Aluminium oxide (D) Calcium oxide Among the following the one which is composed of all the three kinds of bonds (ionic, covalent and coordinate bond) is: (A) Sodium chloride (B) Ammonia (C) Carbon tetrachloride (D) Ammonium chloride During ionization metals lose electrons, this change can be called: (A) Oxidation (B) Reduction (C) Redox (D) Displacement Duralumin is an alloy of: (A) Aluminium, copper, magnesium and iron (B) Zinc, copper, aluminium, and manganese (C) Aluminium, magnesium, manganese and copper (D) Magnesium, manganese, aluminium and tin (d) Write balanced equations for the following reactions : Sulphur and concentrated nitric acid. Bromoethane and an aqueous solution of sodium hydroxide. 247

2 X - ICSE (Chemistry) MT EDUCARE LTD. (e) Concentrated hydrochloric acid and potassium permanganate solution. Excess ammonia reacts with chlorine. Draw the structural formula for the following compounds. Also write the correct IUPAC name for each compound : iso butane neo - pentane (f) Calculate the number of moles and the number of molecules present in 2.6 gms of acetylene. (atomic weights : C = 12, H =1) Also calculate the vapour density of acetylene. [3] (g) (h) (j) (k) (l) Identify the anion in each of the following compounds A, B, C and D given below : When compound A is made to react with Barium chloride solution a white precipitate is formed which is insoluble in dilute nitric acid or dilute hydrochloric acid. When a solution of compound B is made to react with silver nitrate solution a white precipitate is formed which is soluble in excess of ammonium hydroxide solution. When a freshly prepared solution of ferrous sulphate is added to a solution of D and concentrated sulphuric acid is gently poured from the side of the test-tube, a brown ring is formed. Some word/words are missing in the following statements. Rewrite the statements in the correct form using the appropriate word/words. Hydrochloric acid is prepared in the laboratory by passing hydrogen chloride directly through water. Lead bromide conducts electricity. Calculate the percentage of water of crystallization in green vitriol crystals, FeSO 4. 7H 2 O. (atomic weights: Fe = 56, S = 32, O = 16, H = 1) Electrolysis of copper sulphate solution was carried out with copper electrodes: Compare the change in the mass of the cathode with the change in the mass of the anode. Write the ionic equations for the reactions that take place at the electrodes. What happens to the colour of the copper sulphate solution if platinum electrodes are used? Explain this observation. Two acidic solutions have ph = 2 and 6 respectively. What is the ph of the stronger acid? Give the name of the acid salt which gives potassium ions and sulphate ions in solution. (m) Give reasons for the following : Ionization potential of element increases across a period. (n) (o) Write an equation to show the decomposition of nitric acid. Name the process used for the large scale manufacture of sulphuric acid. 248

3 MT EDUCARE LTD. X - ICSE (Chemistry) SECTION - II (Attempt any four questions) Question 2. (a) The following questions are relevant to the extraction of aluminium : Why is caustic alkali added to bauxite ore during the purification of bauxite? Give a balanced chemical equation for the above reaction. Name the two aluminium compounds in the electrolyte of an electrolytic cell during the extraction of aluminium. Answer the following : Differentiate between calcination and roasting (one point) Give the chemical formula of one main ore of iron. State the property of the metal being utilized in the following: Use of metal Property Zinc in galvanization Aluminium in thermite welding (d) What is the special feature of the apparatus that is used in the laboratory preparation of nitric acid? Why should the temperature of the reaction mixture of nitric acid not be allowed to rise above C? Question 3. (a) Consider the section of the Periodic table given below: group IA IIA IIIA IVA VA VIA VIIA 0 numbers Note: (1) In this table some elements are given in their own symbol and position in the periodic table. (2) Other elements are shown with letters, that is; A, D, E, G, L and M. You must see the position of the element in the periodic table Now answer the following questions, with reference to the table: Which is the most electronegative? Compare the size of the atoms of Li and M. In which case will it be less? Which feature of the atomic structure accounts for the similarities in the chemical properties of the elements in group VIIA? What is the name given to the energy released when an atom in its isolated gaseous state accepts an electron to form an anion? (v) What is the electronic configuration of the element in the third period which gains one electron to change into an anion? (vi) Write the formula of the compound formed between A and L. (vii) In the compound formed between D and G what type of bond will be formed? (viii) Draw an electron dot diagram to show the formation of : Magnesium chloride. (ix) Name the alkaline earth metal in period 3. H Li Be B D N G M Ne A Mg A l Si E L Cl Ar He [9] 249

4 X - ICSE (Chemistry) MT EDUCARE LTD. Alkali metals are good reducing agents. Justify this statement with reasons. Question 4. (a) Name the property of sulphuric acid depending on whether it is dilute or concentrated in each of the following reactions: When sugar turns black in its presence. When it is used in the laboratory preparation of aqua fortis. Acts as a source of hydrogen gas when it is diluted and a strip of magnesium is added to it. When it reacts with sulphur to form sulphur dioxide and water. Which feature of the ammonia molecule leads to the formation of the ammonium ion when ammonia dissolves in water? Name the other ion formed when ammonia dissolves in water. Draw an electron dot diagram to show the structure of ammonium ion. Also state the type of bonding present in it. (d) Why is ammonium nitrate not used in the laboratory preparation of ammonia? Sulphuric acid is a dibasic acid. Explain the statement. Question 5. (a) Of the two gases ammonia and hydrogen chloride, which one is more dense? Name the method of collection of this gas. (d) (e) (f) Which property of hydrogen chloride is demonstrated by the fountain experiment? Write balanced equations for the reaction of dilute hydrochloric acid with each of the following: Sodium hydrogen carbonate Sodium thiosulphate solution A key chain had to be electroplated with nickel to prevent rusting. For this electroplating: Name the electrolyte Name the cathode Name the anode Name the catalyst used in the manufacture of nitric acid by ostwald s process. Write a chemical equation to illustrate the acidic nature of nitric acid. [3] Question 6. (a) Give balanced chemical equations for the following: [State the necessary conditions] The formation of sodium ethoxide from ethanol. The preparation of ethyne from 1, 2 dibromoethane. The reaction of one mole of ethene with one mole of chlorine gas. The formation of ethyl acetate from ethanoic acid. (v) The formation of ethane from ethene. [5] 250

5 MT EDUCARE LTD. X - ICSE (Chemistry) A compound M consist of 20% carbon, 26.67% oxygen, 46.67% nitrogen and 6.66% hydrogen by mass. Determine the empirical formula of the compound M. [atomic weights : C=12, O = 16, N = 14, H = 1] What is the molecular formula of M, if the relative molecular mass of M is 60. What is the composition of aqua regia? Question 7 (a) Give one chemical test to distinguish between the following pairs of substances. The reaction on both the substances must be mentioned. Sulphuric acid and sulphurous acid. Manganese dioxide and copper (II) oxide. State the two substances that will react during the laboratory preparation of the following salts. Also name the method involved in the formation of each salt. Lead chloride Copper sulphate Ferric chloride Calculate the amount of zinc necessary to liberate 1792 cm 3 of hydrogen at S.T.P. from dilute sulphuric acid. (atomic weights: Zn = 65, H =1) [6] 251