class 10 science important questions, chapter 2

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  1. Two solutions A and B have pH values of 5 and 8 respectively. Which solution will be basic in nature?                                              (Delhi  2008)
  2. On adding dilute hydrochloric acid to copper oxide powder, the solution formed is blue-green, predict the new compound formed which imparts a blue-green colour to the solution.           (Delhi  2008)
  3. How does the flow of acid rain water into a river make the survival of aquatic life in the river difficult?            
  4. Write chemical equations to show the reactions taking place when a glass rod dipped in concentrated hydrochloric acid is introduced in a jar containing ammonia gas.                                                      
  5. Which acid is present in sour milk or curd?
  6. Which acid is present in tamarind?
  7. What is aqua regia?
  8. Which chemical is present in enamel?
  9. Do alkalis also react with metals? Give one example
  10. A yellow colour solution turns reddish pink in acidic solution and remains as such in basic solution. What do you call such substances?
  11. Two solutions have pH numbers 7 and 2 respectively. Which solution has more H concentration?
  12. How is the concentration of hydronium ion (H3O+) affected when a solution of an acid is diluted?
  13. Tooth enamel is one of the hardest substances in our body. How does it undergo damage due to eating chocolates and sweets? How do tooth pastes prevent this damage?               
  14. A compound which is prepared from gypsum has the property of hardening when mixed with a proper quantity of water. Identify the compound. Write the chemical equation for its preparation. For what purpose is it used in hospitals?                               
  15. What is meant by water of crystallisation, of a substance? Describe an activity to show that blue copper sulphate crystals contain water of crystallisation.                                                 
  16. A compound X of sodium is commonly used in kitchen for making crispy pakoras. It is also used for curing acidity.
  17. What is Baking powder? How does it make the cake soft and spongy?  (Delhi   2008)
  18. Write the chemical formula for washing soda. How may it be obtained from baking soda? Name an industrial use of washing soda other than washing clothes.                                                          
  19. Write the chemical formula for bleaching powder. How is bleaching powder prepared? For what purpose is it used in paper factories?    (AI 2008)
  20. Write the chemical formulae of washing soda and baking soda. Which one of these two is an ingredient of antacids? How does it provide relief in stomach ache?                                                         
  21. (a) Give Arrhenius definition of an acid and a base. (b) Choose strong acid and strong base from the following; CH3COOH, NH4OH, KOH, HCL (Delhi 2007)
  22. A metal compound A, react with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
  23. Why does distilled water not conduct electricity whereas rainwater does?
  24. A milkman adds a very small amount of baking soda to fresh milk. (a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline? (b) What do you expect to observe when the milk comes to a boil? (c) Why does this milk take a long time to set as curd?
  25. Baking soda is used in small amount in making bread and cake. It helps to make these soft and spongy. An aqueous solution of baking soda turns red litmus blue. It is also used in soda acid fire extinguisher. Use this information to answer the following questions; (i) How does Baking soda help to make cakes and bread soft and spongy?  (ii) How does it help in extinguishing fire? (iii) Is the pH value of baking soda solution lower than or higher than?                                                            (CBSE  2009)

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