7 a..Oil and fat containing flushed with nitrogen, why?
b. why we apply paint on iron articles?
8. Observe the given figure and answer the following questions (figure 1.9 page no: 11 in text book)
1) Write the complete balanced reaction for the above
2) Type of reaction involved
3) Is there any precipitate formed?
4) If there any precipitate formed, write the color of the precipitate formed.
9. A student dropped a few pieces of marble in dilute hydrochloric acid, contained in a test-tube. The evolved gas was then passed through lime water. What change would be observed in lime water? What will happen if excess of gas is passed through lime water? Write the balanced chemical equations for all the changes observed.
10. When a metal X treated with cold water, it gives a base Y with molecular formula XOH (molecular mass=40) and liberates a gas Z which easily catches fire. Identify X, Y and Z and also write the reaction involved.
11. Give an example of a decomposition reaction. Describe an activity to illustrate such a reaction by heating.
12. A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and mention the type of the reaction?
13. Why do we store silver chloride in dark colored bottles?
14. What would you observe when zinc is added to solution of aluminum sulphate?Name the type of reaction and write the chemical equation.
15. Classify the following as acidic basic and neutral. Potassium sulphate,ammonium chloride, sodium sulphate,sodium carbonate and sodium chloride.
16. Write the balanced equation for the following reaction and write the name of the reaction
Barium chloride+ Aluminium sulphate------------------Barium sulphate +sodium chloride
17. a)What will you observe when dilute hydrochloric acid is added to a small amount of copper oxide in a beaker.
18. Solid calcium oxide was taken in a container and water was added slowly to it.
a) Write the observation
b) Write the chemical formula of the product formed
19. What happens when CO2 is bubbled through lime water
a) In small amount
b) In excess
20. A) What happens chemically when quick lime is added to water?
b) Balance the following equation
MnO2 + HCl-----------------MnCl2 +Cl2 + H2O
21. Balance the following:
Fe + H2O --------------Fe3O4 + H2
22. Aqueous solution of lead nitrate and KI are mixed together .What change in colour will you observe? Write the balanced equation and the type of the reaction.
23. In the electrolysis of water,
i) Name the gas collected at anode and cathode
ii) Why is the volume of gas collected at one electrode double the other?
24. Most metals do not react with bases but Zn metal does. Suggest a reason and write an equation for the reaction between Zn and NaOH.
25) A, B, C are three elements which undergo chemical reactions according to the chemical equations
A2O3 + 2B------------B2O3 + 2A
3CSO4+ 2B--------------B2(SO4)3 + 3C
3CO + 2A ----------------A2O3 + 3C
Answer the following questions with reasons a) which element is more reactive?
b) Which element is least reactive? c) What is the type of the reactions listed above?
26) What is redox reaction? Identify the substance oxidized and reduced in the following reactions
i) MnO2 + 4HCl ------------------MnCl2 + 2H2O + Cl2
ii)CuO +H2-----------------------Cu + H2O
27) What is meant by skeletal equation?
28) An aluminum can can be used to store Ferrous sulphate solution. It is observed that in a few days holes appeared in the can.Explain the observation and write the chemical equation to support your answer.
29) What is the brown coloured gas evolved when lead nitrate crystals are heated in a dry test tube?
30) Identify the substance that is oxidized and reduced in the reaction
CuO +Zn -----------------------Cu+ ZnO
31. A solution of copper sulphate was kept in an iron pot. After few days, the iron pot developed some holes in it.How will you account for this?
32)A student prepared solutions of an acid and a base in two separate beakers. She forgot to label the solutions and litmus paper is not available in the lab.Since the two solutions are colorless how will she distinguish the two?
33)A compound which is formed due to the recrystallization of sodium carbonate. Identify the compound and write the chemical formula.
7a) Oil and fat containing food is flushed with nitrogen because nitrogen is an inert gas at room temperature and thereby prevents oxidation of the food.
b) We apply paint on iron articles to prevent the corrosion of theses articles.
8 1)) Na2SO4 + BaCl2 --- BaSO4 + 2NaCl
2) Double Displacement reaction and Precipitation reaction
4) Whit Precipitate is formed.
9) The gas passed through lime water turns it milky
Ca(OH)2 + CO2 ----- CaCO3 + H2O
When excess of the gas is passed
CaCO3+H2O+Ca(OH)2 ----------- CaHCO3