Chemistry (Standard 9 th )

Transcription

1 Chemistry (Standard 9 th ) Subjective (60 Marks) Answer any six of the following questions: Que. 1. a) Write the names of the following compounds: i. Al 2 (SO 4 ) 3 ii. Mg(HCo 3 ) 2 b) Give the names of the following: i. Ca(OH) 2 ii. HCL c) Write formula and balance the following equation: (3 Marks) i. Zinc + dil Sulphuric acid Zinc Sulphate + Hydrogen ii. Zinc Carbonate Zinc Oxide + Carbondioxide iii. Sodium nitrate Sodium nitrate + Oxygen d) Balance the following equations: (3 Marks) i. MnO 2 + HCL MnCl 2 + H 2 O + Cl 2 ii. NH 3 + O 2 N 2 + H 2 O iii. MgCl 2 + Na 2 CO 3 MgCO 3 + NaCl Que. 2. a) State three ways by which proton differs from electron. (3 Marks) b) What do you understand by the following terms: i. Nucleus ii. Nucleons c) State Rutherford s structure of atom. d) State Bohr s model of structure of atom. e) Who discovered Nuetrons. (1 Mark) Que. 3. a) An atom of an element is represented as X. (5 Marks) i. What does the numeral 23 indicate? ii. What does the numeral 11 indicate? iii. What is the number of protons in X? iv. What is the number of electrons in X? v. How are the electrons distributed around the nucleus of X? b) Fill in the blank spaces with appropriate words: (3 Marks) i. The number of protons in the nucleus of an atom is called its. ii. The number of protons and neutrons present in the nucleus of an atom is called. iii. An atom has mass number 35 and the atomic number 17. The number of neutrons in its nucleus are. c) What do you understand by the term electronic configuration? State Bohr-Bury scheme of electronic Confirguration?

2 Que. 4. a) From the list of elements given below, make three triads and name the family of each traid: CL, Li, Ca, Br, Na, Sr, I, K and Ba b) (5 Marks) i. Name an alkali metal other than Lithium, Sodium and Potassium. ii. Name an alkaline earth metal other than Calcium, Strontium, Barium. iii. Name the halogen other than Chlorine, Bromine and Iodine? iv. Name a non-metal having properties similar to carbon? v. Name a rare gas other than Neon, Krypton and Xenon? c) Why was the classification on the basis of law of traids rejected? d) Define modern periodic table. (1 Mark) Que. 5. a) Table given below shows the mass number and number of neutrons in four elements P, Q, R and S. (5 Marks) Elements P Q R S Mass Number Number of neutrons i. Write down the atomic number of P, Q, R and S. ii. Write down electronic configuration of P, Q, R and S. iii. To which group P, Q, R and S belong? iv. To which period P, Q, R and S belong? v. Which amongst the P, Q, R and S is the noble gas? b) Name four alkali metals metals. To which group do they belong? c) The elements A and B have electronic configuration (2, 8, 18, 2) (2, 6) respectively. (2) i. To which periods A and B belong? ii. To which group A and B belong? d) Define Mendeleev s Periodic law? (1 Mark) Que. 6. a) State two merits of Mendeleev s periodic law over previous attempts of classification of elements. b) State two achievements of the law of octaves? c) With reference to long form of periodic table fill in the blanks spaces with appropriate words: (5 Marks) i. The chemical properties of an element are the periodic function of their. ii. The serial number of an element in a periodic table is also its. iii. The number of electrons in valence shell of an atom represents its in the periodic table. iv. elements are placed on the right hand side of the periodic table. v. The elements occupying left and right wing vertical columns are called elements.

3 d) Mention first element of 7A group? (1 Mark) Que. 7. a) Name the two metals which react: i. With cold water to form hydrogen. Write balanced chemical equations. (1 Mark) ii. Name two metals which react with steam and displace hydrogen. Write the balanced chemical equation? iii. How is hydrogen prepared industrially by Bosch process? (3 Marks) b) Why does hydrogen gas collected from zinc has a characteristic fishy smell? c) Name the chemicals used in purification of hydrogen gas prepared from granulated zinc? Que. 8. a) K, Na, Ca, Mg, Al, Zn, Fe, Sn, Pb, H, Cu, Hg, Ag and Au constitute activity series. Answer the following questions: (5 Marks) i. Name the metal which reacts fastest with cold water, but reacts with boiling water not very slowly. ii. Name a metal which on heating reacts with steam but reaction is reversible. iii. Name a metal which reacts explosively with dil HCL. iv. Name a metal which reacts vigorously with dil HCL. v. Name a metal which displaces hydrogen very slowly from dil HCL b) How is hydrogen prepared industrially by Bosch process? (3 Marks) c) Name the metal which does not react with water or dil HCL. Que. 9. a) How is sulphur dioxide added into the atmosphere by the human activities? (3 Marks) b) How is acid rain caused? (3 Marks) c) Breifly state problems created by acid rain? d) What do you understand by term green house effect? Que. 10. a) How does ozone layer protect living beings on the surface of the earth? b) Suggest two methods to control the destruction of the ozone layer? c) Suggest three ways of controlling global warming? (3 Marks) d) Breifly describe the nature of infrared rays? (3 Marks) Que. 11. a) Give the name and the symbol of the following elements which occupy each of the following positions in the periodic table: (5 Marks) i. Period 2, Group 3A ii. Period 1, Group 1A iii. Period 4, Group zero iv. Period 2, Group 6A

4 v. Period 3, Group 7A b) Which period shortest, longest and incomplete in the long form of periodic table? (3) s)where would you except to find the element with atomic number 20 in the periodic table and why? Que. 12. a) i. What is the other name of noble gas? (1 Mark) ii. Why are atoms of noble gas unreactive? (1 Mark) iii. Choose the inert gases from the following list: H, He, Na, Ne, Au, Ar, K, Kr, Ra, Rn, Xe. b) Which of the following elements would you except to be most stable and why?(4 Marks) 2 4 A, B, C, D. c) Name a noble gas which has less than 8 electrons in its valence shell. What is the atomic number of this gas? Que. 13. a) (5 Marks) i. Explain why 3 2 He and 3 1 He are not considered as isotopes? ii. Why do these isotopes have similar chemical properties? iii. Why are these isotopes electrically neutral? b) The composition of two atoms P and Q is given below: (5 Marks) Atom Neutrons Protons Electrons P Q i. What is the mass number of P? ii. What is the mass number of Q? iii. How are P and Q related to each other? iv. Which elements do these atoms represent? v. Are the elements metals or non-metals? Que. 14. a) Fill in the blanks with appropriate words: i. Isotopes have different number because their nuclei contain different number of. ii. Some carbon atoms have mass number 12 and some have mass number 14. These atoms of different mass numbers are called. b) An element is represented by symbol X: (3 Marks) i. What is the mass number and atomic number of element X? ii. Name its valence shell and number of electrons in valence shell? iii. Is the element metal or non-metal? c) The ratio of isotopes Cl and Cl in natural chlorine is 1:3. Calculate the fractional atomic mass of chlorine? (3 Marks) d) State the number of valence electrons in alkali metals and halogens?

5 Q-15) The composition of two atoms A and B is given below : (5marks) Atom Neutrons Protons Electrons A B (1) What is the mass no of P? (2) What is the mass no of Q? (3) Which element do these atoms represent? (4) How are P and Q related to each other? (5) Are the elements metals or non metals? (b) The elements ( At. No. 2), B (At. No. 7), C (At. No. 10), and E (At. No. 17) have atomic masses 4,14,20 and 40 and 35 respectively. Write the no of protons, number of neutrons, and number of electrons and electronic configuration of each of the element and hence state which of them are the members of noble gases and why? Q-16. (a) Which of the element would you expect chemically inert and why (1) P, Q, 2 4 R, s, T (5 marks) (b) Ne, Ne, Ne, are the isotopes of neon (3 marks) (1) What do the superscript and superscript represent? (2) What is the cause of change in superscript? (3) Give the geometric diagram of Ne. (c ) what is the main cause of existence of isotopes? (2marks) Q 17 ( a) Define environment, pollution, and atmospheric pollution? (3marks) (b) Name the two harmful effects of carbon monoxide on human health? (2marks)

6 ( c) What is the main source of methane and the color of ozone gas? (3 marks) ( d) What are the main sources from which ( C F C) are released? (2 marks) Q 18 (a ) What are the primary pollutants? ( 2 marks) ( b) Write a note on natural sources of air pollutants? ( 3 marks) ( c) What are the water pollutants? ( 2 marks) ( d ) suggest three measures to control water pollution? ( 3 marks) Q 19. ( a) How are the impurities present in hydrogen gas are removed? (3 marks) ( b) What precautions should be taken during the laboratory preparation of hydrogen? (3 marks) points? ( c ) What are the similarities between hydrogen and halogen.mention atleast 4 ( 4 marks) Q -20. ( a) State four uses of hydrogen gas ( 4 marks) ( b) Describe briefly,with equation,the Bosch process for the large scale production of hydrogen? (4 marks) ( c ) Comment on dual position of hydrogen in the periodic table? ( 2 marks) Q- 21 ( a) Give the basic difference between Mendellev s periodic law and modern periodic law? (2marks) ( b) What is the cause for the periodicity of properities of he elements?which is the longest period in the periodic table? ( 3 marks) ( c) Which is the longest and shortest period in the periodic table? ( 2 marks) ( d) why are nitric acid and hot concentrated sulphuric acid not used in the preparation of hydrogen? ( 3 marks) Q-22. (a) Give the two example s of the compound where the octet rule is not obeyed? (2 marks) ( b) state five properities of ionic compounds? (5 marks)

7 ( c) What is the coordinate covalent bond? Under what circumstances a coordinate covalent bond is formed? ( 3 marks) Q- 23. The electronic configurations of four elements A,B,C,D are given below.usingthese, answer he following questions. ( a) 2,8,18,8, 1 ( b) 2, 8, 7 ( c) 2,8,18,7 ( d) 2, 8, 4 (10 marks) (1) Which of these elements are electropositive elements? (2) Which of these elements are electro negative elements? (3) What will be the formula of molecule formed when A combines with B? Describe the nature of chemical bond formed? (4) What will be the formula of molecule formed when b combines with D? Describe the nature of chemical bond formed? (5) What will be the formula of the molecule of the molecule when C combines with D? Describe the nature of chemical bond formed? (6) What will be the formula of the molecule formed when atoms of B combine among themselves? Describe the nature of chemical bond formed? Q-24. ( a) How would you explain the fractional atomic mass ( 35.5) of chlorine? ( 3marks) ( b) Writhe the electronic configuration of (1) Aluminum (2) Phosphorous ( 2 marks) ( c ) Give two conditions under which the cathode rays are produced? ( 2 marks) ( d) How are the orbits represented around the nucleus? ( 3 marks) Q 25. ( a) Write the formula of the following compounds : ( 10marks) (1) Berium sulphate (2) Bismuth nitrate (3) Calcium bromide (4) Chromium Sulphate (5) Ferrous sulphide (6) Magnesium Phosphate (7) Potassium ferrocynade (8) Stannic oxide (9) Calcium silicate 10) Sodium Zincate.

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