CLASS - XI
Unit 1 Some basic Concepts of Chemistry
1 . Define law of multiple proportions with example.
2. Calculate the molecular mass of C1 2H22O1 1
3. Calculate the no. of atoms present in 1 1 .5 litres of H2at N.T.P.
4. Calculate the no. of moles of 5.68 gm. of iron.
5. What is the effect of temp. on molality and molarity?
6. An atom of an element is 1 0.1 times heavier than the mass of a carbon atom. What is its
mass in a.m.u.?
7. Explain with example, limiting reagent.
8. Differentiate between molarity and molality.
9. 1 .82 g. of glucose (molar mass-1 80) is dissolved in 25g of water. Calculate (a) the
molality (b) mole fraction of glucose and water.
1 0. The molecular mass of an organic compound is 90 and its %age composition is C26.6% ; O=71 .1 % and H=2.2% . Determine the molecular formula of the compound.
1 1 . Verify law of Reciprocal proportions or law of equivalent proportions, with example.
1 2. Commercially available sulphuric acid contains 91 % acid by mass and has a density
of 1 .83g mL-1 (i) Calculate the molarity of the solution (ii) volume of concentrated acid
required to prepare 3.5L of 0.50 M H2SO4
1 3. A compound contains 4.07% hydrogen, 24.27% carbon and 71 .65% of chlorine. Its
molar mass is 98.96g. What are its empirical and molecular formulas?
1 4. What is Gay Lussac's law? Explain with two examples.
1 5. What are empirical and molecular formulae? How are they related to each other?
1 6. Why molality is preferred over molarity in expressing the concentration of a solution?
1 7. Explain with the help of an example law of conservation of mass and energy and also
the law of constant proportions.
18. How much potassium chlorate should be heated to produce 2.24L of oxygen at NTP? [2]
19. Calculate the weight of lime (CaO) obtained by heating 2000kg of 95% pure lime stone
(CaCO3) [2]
20. 4 litres of water are added to 2L of 6 molar HCl solutions. What is the molarity of resulting
solution? [2]
21. What volume of 10M HCl and 3M HCl should be mixed to obtain 1L of 6M HCl solution? [2]
22. At NTP, what will be the volume of molecules of 6.022 *1023 H2? [1]
23. Calculate the number of molecules present in 0.5 moles of CO 2? [1]
24. 1L of a gas at STP weighs 1.97g. What is molecular mass? [1]
25. Write empirical formula of following – [4]
CO, Na2CO3, KCl, C6H12, H2O2, H3PO4, Fe2O3, N2O4.
26. Calculate the number of moles in the following masses – [2]
(i) 7.85g of Fe
(ii) 7.9mg of Ca
27. Vitamin C is essential for the prevention of scurvy. Combustion of 0.2000g of vitamin C
gives 0.2998g of CO 2 and 0.819g of H2O. What is the empirical formula of vitamin C? [3]