Friday, May 25, 2012

X Chemistry : Chapter 01: Chemical reactions and equation

X Chemistry : Chapter 01: Chemical reactions and
ASSIGNMENT – 1, SESSION – 2012-2013
1. What change do you observe, when magnesium ribbon is burnt in air?
2. Give reason - Magnesium ribbon is to be cleaned before burning in air.
3. Define the term word equation?
4. Name the term used for the physical state of the solution of the reactant or product dissolved in water.
5. Write an example of decomposition reaction.
6. What is meant by thermal decomposition?
7. Name the chemical reaction in which heat is absorbed.
8. Name the gas which burns with a pop sound.
9. Name the type of reaction in which two or more substances combine to form a new single product.
10. What is Redox reaction?
2 and 3 marks questions
Q.1 Express the following reactions in the form of chemical equations and balance them. Make an equation as informative as you can. Also mention the type of reaction :-
(a) When solid mercury (II) oxide is heated, liquid mercury and oxygen gas are produced.
(b) Ethyne (C2H2) gas burns in oxygen to form carbon dioxide and water along with evolution of heat.
(c) Phosphorus burns in oxygen to form phosphorus pentaoxide.
(d) Magnesium ribbon is burnt in a jar containing nitrogen gas when a white powder of magnesium nitrite is obtained.
(e) Marble dissolves in HCL acid to give calcium chloride; water and carbon dioxide.
Q.2 Balance the following chemical reations :-
(a) CS2 + O2 -------------> CO2 + SO2 (b) CaC2 + H2O -------------> Ca(OH)2 + C2H2
(c) Al(OH)3 -------------> Al2O3 + H2O (d) H2O2 -------------> H2O + O2
(e) Cu + AgNO3 -------------> Cu(NO)3 + Ag (f) SO2 + H2S -------------> H2O + S
(g) Mg3N2 + H2O Mg(OH)2 + NH3 (h) Mno2 + H2SO4 -------------> MnSO4 + H2O + O2
(i) KClO3 -------------> KCl + O2 (j) Ni(NO3)2 + NaOH Ni (OH)2 + NaNO3
Q.3 Name the substances oxidized, reduced, oxidizing agent and reducing agent in the following reactions :-
(a) 3MnO2 + 4Al -------------> 3Mn + 2Al2O3
(b) Fe2O3 + 3CO -------------> 2Fe + 3CO2
(c) H2S + HNO3 -------------> NO + S + H2O
(d) H2S + Cl2 -------------> 2HCl + S
(e) PbS + 4 H2O2 → PbSO4 + 4 H2O
Q.4 i) State two uses of chemical decomposition reaction in industry.
ii) What kind of chemical reaction takes place during the digestion of food?
Q.5. Correct the formulae and balance the following equation.
K(s) + H2(l) ------------->KOH(aq) + H2(g)
Q.6 Write fully balanced chemical equation and state the physical condition and physical state of the reactants in the following reaction. Aluminium metal dissolves in aqueous copper sulphate solution with the formation of aluminium sulphate and copper.
(i) What do you understand by the following terms used in a chemical equation :
(a) reactants (b)products?
(ii) What does symbol ( aq ) represent in a chemical equation ?
Q.7 A substance X, which is an oxide of a group 2 element, is used intensively in the cement industry. This element is present in bones also.
On treatment with water it forms a solution which turns red litmus blue. Identify X and also write the chemical reactions involved
Q.8 Which among the following are physical and chemical changes? (a) Evaporation of petrol. (b) Burning of Liquefied Petroleum Gas(LPG) c)Heating of an iron rod to red hot.(d) Curdling of milk.(e) Sublimation of solid ammonium chloride.
Q.9. Zinc and aluminium are very high in metal activity series, yet they resist corrosion to a great extent. Explain.
Q.10 Why are halides (chloride, bromide, and iodide) of silver kept in dark brown or black bottles?
Q.11 A, B and C are three elements which undergo chemical reactions according to the following equations -
A2O3 + 2B → B2O3 + 2A
3CSO4 + 2B→ B2(SO4) + 3C
3CO + 2A→ A2O3 + 3C
Answer the following questions with reasons :
(a) Which element is the most reactive?
(b) Which element is the least reactive?
(c) What is the type of reactions listed above?
Q.12 Brightly polished iron nails are placed in copper nitrate solution. Describe all that you will observe after one hour.
5 marks questions:-
Q 13. Name the type of chemical reactions taking place when:-
(i) Lime stone is heated.
(ii) Magnesium ribbon is burnt in air.
(iii) Iron nails are dipped in copper sulphate solution.
(iv) Burning of coal.
(v) Sodium sulphate is mixed with barium chloride.
Q 14. Balance the following chemical reactions and state the type of chemical reactions:- (i) On Passing (2) Electric Current
(i) H2O → H2 + O2
(ii) CaO + H2 O → Ca(OH)2
(iii) 2 2 CuO + H2 →Cu + H2 O
(iv) Pb + CuCl2 → PbCl2 + Cu (v) FeSO4 → Fe 2O + SO3 + SO2
Q 15. Translate the following statements into chemical equations and balance them :-
(i) Sodium chloride reacts with silver nitrate to give sodium nitrate and a precipitate of silver chloride.
(ii) Hydrogen gas combines with nitrogen to form ammonia.
(iii) Zinc carbonate decomposes to give zinc oxide and carbon dioxide.
(vi) Ammonia gas reacts with water to give ammonium hydroxide.(v) Copper (II) oxide on heating with hydrogen gas gives copper and water.

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