#### Most expected three mark questions in Basic Concepts of Chemistry and Chemical Calculations - II

11th Standard

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Chemistry

Time : 02:30:00 Hrs
Total Marks : 150

Part - A

50 x 3 = 150
1. (i) If an acid is mono basic, how will you relate their equivalent mass and molecular mass.
(ii) What is the basicity of H4 P2 O7 ?
(iii) Give any two examples for dibasic acids.

2. Why are the atomic mass of most of the elements fractional?

3. Write down the formulae for calculating the equivalent mass of an acid, base and oxidizing agent.

4. 1.05g of a metal gives on oxidation 1.5g of its oxide. Calculate its equivalent mass.

5. Calculate Equivalent mass of the Hydrochloric acid

6. Calculate Equivalent mass of the Nitric acid

7. Calculate Equivalent mass of the Acetic acid

8. Calculate Equivalent mass of the Crystalline oxalic acid

9. Calculate Equivalent mass of the Phosphorous acid

10. Calculate the number of moles in the following 7.85 g of copper

11. Calculate the number of moles in the following 4.66 mg of silicon

12. Calculate the number of moles in the following 65.6 mg of oxygen

13. What will be the molecular formula for the compound, whose empirical formula is CH2CI and molar mass is 98.96 g?

14. A compound on analysis was found to contain C = 34.6%; H = 3.85% and O = 61.55%. Calculate its empirical formula.

15. Balance the following reaction by oxidation number method.

16. Calculate equivalent mass of the Sodium hydroxide

17. Calculate equivalent mass of the Aluminium hydroxide

18. Calculate equivalent mass of the Ammonium hydroxide

19. Calculate equivalent mass of the Calcium hydroxide

20. Calculate equivalent mass of the Magnesium hydroxide

21. Calculate the equivalent mass of potassium dichromate in acid medium
[K2Cr2O7 + 4H2SO4 )$\rightarrow$K2SO4 + Cr2(SO4)3 +4H2O + 3(O) 3 x 16 = 48 294 g]

22. 3.24g of titanium reacts with oxygen to form 5.40g of the metal oxide. Find the empirical formula of the metal oxide?

23. A compound contains 11.99 % N, 13.70 % 0, 9.25 % B and 65.06 % F. Find its empirical formula

24. A organic compound used for welding operation contains the following composition by mass: C = 92.3%, H= 7.7%. Find out the molecular formula of the compound. At STP, 10.0 L of this gas is found to weigh 11.6g.

25. The organic compound Vitamin-C, has the following composition by mass: 40.92% C, 4.58% H, and the rest is oxygen. Determine its molecular formula. Molar mass of the substance is 176 g mol-1

26. A piece of cut apple becomes brown. Why? Can you prevent it by a simple method

27. Place an iron piece in a moist atmosphere and observe it after two days. Is there any deposition of new substance? Why does it happen? What is this phenomenon called?

28. An iron nail is placed in copper sulphate solution  taken in the beaker. Observe it for some time?Find the changes that takes place and why?

29. Calculate the oxidation number of underlined atoms ${ K }_{ 2 }\underline { Mn } { O }_{ 4 }$

30. Define stoichiometry.

31. The percentage of all the elements present o in a compound is 95. What does it indicate?

32. Why is it necessary to balance a chemical equation?

33. What do you understand by stoichiometric coefficients in a chemical equation?

34. The reactant which is entirely consumed in reaction is known as limiting reagent. In the reaction 2A + 4B $\longrightarrow$ 3C + 4D, when 5 moles  of A react with 6 moles of B, then
(i) Which is the limiting reagent
(ii) Calculate the amount of C formed.

35. What is the simplest formula of the compound which has the following percentage composition?  C = 80%;  H = 20%

36. How are 0.5 mol Na2CO3 and 0.50 M Na2CO3 different?

37. Write the simplest formula for the following. - N2O4

38. Write the simplest formula for the following. - C6H12O6

39. Write the simplest formula for the following. - H2O

40. Write the simplest formula for the following. - H2O2

41. Elucidate the steps involved in arriving at the molecular formula of a compound.

42. Calculate the molecular mass of the following KMnO4

43. Calculate the molecular mass of the following Crystalline oxalic acid

44. Calculate the molecular mass of the following Methane

45. Calculate the oxidation number of underlined atoms $H_{ 4 }\underline { { P }_{ 2 } } { O }_{ 7 }$

46. Calculate the oxidation number of underlined atoms $\underline { C } l{ O }_{ 3 }$-​​​​​​​

47. Calculate the oxidation number of underlined atoms $\underline { A } sO_{ 3 }^{ 3- }$

48. Calculate the oxidation number of underlined atoms $\underline { { S }_{ 2 } } { O }_{ 3 }$

49. Calculate the oxidation number of underlined atoms${ C }_{ \underline { 6 } }{ H }_{ 12 }{ O }_{ 6 }$

50. Calculate the oxidation number of underlined atoms $\\ { Na }_{ 2 }[\underline { F } e{ (CN) }_{ 6 }]$

51. Calculate the number of atoms/molecules present in the following: 10 g of Hg

52. Calculate the number of atoms/molecules present in the following 1.8g of water

53. Calculate the number of atoms/molecules present in the following 100g of sulpur dioxide