class 11 important questions as well as important points chapter wise

                                                    CLASS - XI CHEMISTRY

                              (Basic Concepts of Chemistry)   

    

                   Topic: - Mole concept, percentage composition

Marks: 20 

1. What is the value of one mole?        [1]

2. At NTP, what will be the volume of molecules of 23 6.022 10 × H2?    [1]

3. Calculate the number of molecules present in 0.5 moles of CO2?    [1]

4. Give one example each of a molecule in which empirical formula 

 and molecular formula are (i) same (ii) Different.      [2]

5. 1L of a gas at STP weighs 1.97g. What is molecular mass?     [1]

6. Write empirical formula of following –       [4]

  CO, Na2CO3, KCl, C6H12, H2O2, H3PO4, Fe2O3, N2O4. 

7. Calculate the number of moles in the following masses –     [2]

 (i) 7.85g of Fe 

 (ii) 7.9mg of Ca
 

8. Vitamin C is essential for the prevention of scurvy. 

 Combustion of 0.2000g of vitamin C gives 0.2998g of CO2 

and 0.819g of H2O. What is the empirical formula of vitamin C?    [3]