Subject: Science, asked on 21/3/12

Subject: Science, asked on 31/5/13


Q1.What type of chemical reaction takes place when chlorine gas is passed through an aqueous solution of Potassium bromide?

Q2.Which element is used for galvanization of iron?

Q3.Give the name of one natural and one synthetic antioxidant.

Q4.What is the significance of symbol ‘aq.’?

Q5.How many atoms of oxygen are present in 0.1 mole of water?


Q6.Why does milk become sour if kept for a long time?

Q7.What is the name of compound present in air that causes silver to tarnish? Give the reaction.

Q8.What is the colour of Ferrous sulphate crystals? How does this colour change upon heating?

Q9.What is an oxidation reaction? Give an example of oxidation reaction. Is oxidation an endothermic or exothermic reaction?

Q10. Can a displacement reaction be a redox reaction? Explain with an example.

Q11.With the help of an activity show that photo decomposition is an endothermic reaction.


Q12.When Lead nitrate is heated, which colour fumes are evolved? Also name the gas evolved.

Q13.A blue colour inorganic compound when heated with Hydrogen sulphide gives black precipitate and aqueous solution of Sulphuric acid. Write the balanced chemical equation.

Q14.Identify which one of the following is a chemical change with reason for the same:

1.souring of milk 2.evaporation of water 3.dissolution of sugar in water

Q15.Awhite salt on heating decomposes to give brown fumes and yellow residue is left behind. Name the salt; write the reaction involved and the type of reaction.

Q16.A Magnesium ribbon is burnt in oxygen to give a white compound X accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound Y.

(i).Write the chemical formulae of X and Y

(ii).Write the balanced chemical equation when X is dissolved in water

Q17.When Calcium oxide is added to water taken in a beaker, rise in temperature is observed. However, when Barium hydroxide is mixed with Ammonium chloride, a fall in temperature is observed. Why?


Q18.What is corrosion? Why do aluminum sheets not corrode easily? Why is a copper vessel covered with a green coating in the rainy season?

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