CHAPTER-1 BASIC CONCEPTS IN CHEMISTRY THEORY ASSIGNMENT CLASS XI

1.       What will be the mass of one atom of C-12 in grams?

2.       Calculate the average atomic mass of hydrogen using the following data :

Isotope               % Natural abundance                Molar mass

¹H                           99.985                                                   1

²H                           0.015                                                     2

3.        Hydrogen gas is prepared in the laboratory by reacting dilute HCl with

granulated zinc. Following reaction takes place.

Zn + 2HCl ⎯→ ZnCl₂ + H₂

Calculate the volume of hydrogen gas liberated at STP when 32.65 g of zinc

reacts with HCl. 1 mol of a gas occupies 22.7 L volume at STP; atomic mass of

Zn = 65.3 u.

      4.      The density of 3 molal solution of NaOH is 1.110 g mL^–1. Calculate the molarity

of the solution.

     5.       Volume of a solution changes with change in temperature, then, will the molality

of the solution be affected by temperature? Give reason for your answer.

     6.       If 4 g of NaOH dissolves in 36 g of H₂O, calculate the mole fraction of each

component in the solution. Also, determine the molarity of solution (specific

gravity of solution is 1g mL–1)

      7.      The reactant which is entirely consumed in reaction is known as limiting reagent.

In the reaction 2A + 4B → 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?