SOME BASICS.pdfhhjghhjghghghjvnhbnhbnmbmnbnmbm

nbmnnmbnmm m mmbnmbnmnnmn

1. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
1. What weight of sodium chloride is decomposed by 4.9 g of sulphuric acid if
5.2 g of sodium bisulphate and 2.635 g of hydrogen chloride are produced in
the same reaction? Ans : 2.935 g

2. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
2. 8.3 g of sodium bicarbonate is added to 17 g acetic acid solution, CO
2 formed is
allowed to escape. The mass of the solution left is 20 gram. What is the mass of
CO
2 formed? Ans : 5.3 g

3. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
3. Tin forms two oxides. One contains 46.67% of the metal and another 63.94% of tin.
Show that these data are in accordance with the law of multiple proportion.

4. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
4. Weight of copper oxide obtained by treating 2.16 g of metallic copper with nitric
acid followed by ignition was found to be 2.7 g. In another experiment, 1.15 g of
copper oxide on reduction gave 0.92 g of copper. Prove that the results confirm the
law of definite proportions. Ans : Cu = 80% O = 20%

5. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
5. In an experiment 2.4 g of iron oxide on reduction with hydrogen give 1.68 g of
iron. In another experiment, 2.9 g of iron oxide produced 2.03 g of iron on
reduction. Prove that the above data is in accordance with law of constant
proportions oxide produced 2.03 g of iron on reduciton. Prove that the above data
is in accordance with law of constant proportions.

6. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
6. Two oxides of a metal contain 57.2% and 72.73% oxygen respectively. Show that
these data confirm the law of multiple proportions.

7. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
7. Nitrogen forms five compounds with oxygen in which 1.0 g of nitrogen combines
with 0.57, 1.14, 1.73, 2.28 and 2.90 g of oxygen respectively. Show that these
figures agree with law of multiple proportions.

8. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
8. 61.8 g of A combine with 80 g of B 30.9 g of A combine with 106.5 g of C. B and C
combine to form CB
2. Atomic weights of C. and B are respecitvely 35.5 and 6.6.
Show that the law of reciprocal proportioned is obeyed.

9. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
9. Copper sulphide contains 66.5% Cu, copper oxide contains 79.99% Cu and sulphur
trioxide contains 40% S. Prove that the data is in agreement with law of reciprocal
proportions.

10. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
10. Hydrogen sulphide contains 94.11% sulphur, water contains 11.11% hydrogen and
sulphur dioxide contains 50% oxygen. Show that these results support the law of
reciprocal proportion.

11. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
11. Two oxides of a metal contain 64.4% and 59.2% metal respectively. If the formula
of first oxide is H
2O
3, find the formula of second oxide.
Ans : MO
2

12. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
12. The relative abundance of various isotopes of silicon is as
28
Si = 92.23%,
29
Si, 4.67
% and
30
Si = 3.10%. What is the average atomic mass of silicon?
Ans : 28.1 amu

13. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
13. Calculate the number of water molecules in 0.05 ml of water.
Ans : 1.673 × 10
21

14. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
14. Calculate the number of carbon and oxygen atoms in 25 g of calcium carbonate.
Ans : 1.5 × 10
23
, 4.515 × 10
23

15. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
15. How many atoms and molecules of phosphorus are present in 124 g P
4?

Ans : 2.4088 × 10
24
atoms, 6.023 × 10
23
molecules

16. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
16. The volume of a gas at STP is 1.12 × 10
–7
ml. Calculate the number of molecules
present in the gas.
Ans : 3.01 × 10
12

17. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
17. How many moles of magnesium phosphate Mg
3(PO
4) will contain 0.25 mole of
oxygen atoms?
Ans : 3.125 × 10
–2

18. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
18. Calculate the total number of electrons present in 1.4 g of nitrogen gas.
Ans : 4.214 × 10
23
electrons

19. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
19. Calculate the mass of Na
2CO
3 which will have the same number of molecules as
contained in 12.3 g of MgSO
4. 7H
2O.
Ans : 5.3 g

20. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
20. Given that the abundances of isotopes
54
Fe,
56
Fe and 5%, 90% and 5% respectively.
What is the atomic mass of iron atom?
Ans : 55.95 u

21. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
21. Glucose solution contains 9 g of glucose (C
6H
12O
6). How many atoms of C, H and
O are present in the solution?
Ans : C and O = 1.806 × 10
23
atoms. H = 3.612 × 10
23
atoms

22. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
22. How many grams of concentrated nitric acid solution should be used to prepare
250 ml of 2.0 M HNO
3? The concentrated acid is 70% HNO
3.
Ans : 45 g

23. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
23. 6.02 × 10
20
molecules of urea are present in 100 ml of its solution. What is the
concentration of solution?
Ans : 0.1 M

24. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
24. Calculate the molarity and normality of a solution containing 3.15 g of hydrated
oxalic acid [(COOH)
2. 2H
2O] dissolved in 250 ml of the solution.
Ans : 0.1 M, 0.2 N

25. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
25. A bottle of sulphuric acid (d = 1.787 g/ml) is labelled as 86% by mass. What is the
molarity of the solution? What volume of the acid is required to make 1 L of 0.2
M H
2SO
4? Ans : 15.68 M, 12.75 ml

26. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
26. Find the molality of 1 litre solution of 93% H
2SO
4 (w/v). The density of solution is
1.84 g/ml.
Ans : 10.428 m

27. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
27. If the density of methanol is 0.793 kg L
–1
, what is its volume needed for making 2.5
L of its 0.25 M solution?
Ans : 25.22 ml

28. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
28. (i) A sample of drinking water was found to be contaminated with chloroform
(CHCl
3) which is carcinogenic. The level of contaimnation was 15 ppm (by mass).
(a) Express its per cent by mass.
(b) Determine the molarity of chloroform in the water sample.
(ii) Calculate the molarity of a solution of ethanol in water in which the mole
fraction of ethanol is 0.040.
Ans : 1.5 × 10
–3
%, 1.26 × 10
–4
M, 2.3145

29. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
29. The density of 3 M solution of NaCl is 1.25 g mL
–1
. Calculate the molality of the
solution.
Ans : 2.79 m

30. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
30. The density of solution prepared by dissolving 120 g urea (mol mass = 60) in 1000
g of water is 1.15 g/ml. What is the molarity of solution?
Ans : 2.79 m

31. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
31. A mixture of Na
2CO
3 has the impurity of NaCl. 4 g of this mixture is dissolved in
250 ml aqueous solution. 25 ml of this solution requires 50 ml of N/10 HCl for
complete neutralisation. Calculate the percentage composition of original mixture.
Ans : Na
2CO
3 = 66.25 %, NaCl = 33.75 %

32. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
32. 2.65 g of diacidic base was dissolved in water and volume was made up to 500 ml.
20 ml of this solution was completely neutralised by 12 ml of N/6 HCl. Find out the
equivalent and molecular mass of the base.
Ans : 53,106

33. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
33. 1.575 of an unknown acid are present in 250 ml of an aqueous solution. 16 ml of
N/8 NaOH solution neutralises 20 ml of the acid solution. If the acid is dibasic,
calculate the equivalent and molar mass of unknown acid.
Ans : 63,126

34. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
34. 1.506 g of limestone was neutralised by 25 ml of a 1.0 N HCl solution. What is the
percentage purity of limestone?
Ans : 83%

35. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
35. 7.35 g of dibasic acid was dissolved in water and diluted to 250 ml. 25 ml of this
solution was neutralised by 15 ml of N – NaOH solution. Calculate the equivalent
weight and molecular weight of acid.
Ans : 49,98

36. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
36. 1.0 g of mixture of anhydrous Na
2CO
3 and K
2CO
3 was made up to 250 ml in
aqueous solution. 25 cc of this solution was neutralised by 20 cc of 0.0812 N HCl.
Calculate the percentage of Na
2CO
3 and K
2CO
3 in the mixture.
Ans : Na
2CO
3 = 40%, K
2CO
3 = 60%

37. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
37. 2.013 g of sample of commercial NaOH containing Na
2CO
3 as an impurity was
dissolved in 250 ml solution. 10 ml of this solution required 20 ml of 0.1 N H
2SO
4
for complete neutralisation. Calculate the percentage by weight of Na
2CO
3 in the
sample. Ans : 2.6%

38. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
38. 0.5 g sample of impure CaCO
3 is dissolved in 50 ml of 0.0985 N – HCl. After the
completion of reaction, the excess HCl requires 6.0 ml of 0.105 N – NaOH for
neutralisation. Determine the percentage of Na
2CO
3 in the sample.
Ans : 43%

39. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
39. 1.64 g of a mixture of CaCO
3 and MgCO
3 were dissolved in 50 ml of 0.8 N – HCl.
The excess of acid required 16 ml of 0.25 N-NaOH for neutralisation. Calculate the
percentage of CaCO
3 and MgCO
3 in the mixture.
Ans : CaCO
3 = 47.98% , MgCO
3 = 52.02%

40. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
40. 0.50 g of mixture of K
2CO
3 and Li
2CO
3 required 30 ml of 0.25 N – HCl solution for
complete neutralisation. What is the percentage composition of the mixture?
Ans : K
2CO
3 = 96%, Li
2CO
3 = 4%

41. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
41. 20 ml of an N/10 NaOH solution neutralises 25 ml of a dibasic acid. The
concentation of this dibasic acid is 6 g/l. What is the molecular weight of the
dibasic acid? Ans : 150

42. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
42. 0.84 g of an acid having molecular mass = 225 is diluted to 100 ml. 25 ml of this
solution neutralises 28.0 ml of 0.1 N NaOH solution. What is the basicity of the
acid? Ans : 3

43. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
43. How many millilitres of a 0.1 N H
2SO
4 solution will be required for complete
reaction with a solution containing 0.125 g of pure Na
2CO
3?
Ans : 23.6 ml

44. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
44. 2.0 g of mixture of NaHCO
3 and KclO
3 requires 100 ml of 0.1 N HCl for complete
neutralisation. What is the composition of the mixture.
Ans : KclO
3 = 1.16 g, NaHCO
3 = 0.84 g

45. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
45. Determine the empirical formula of an oxide of iron which has 69.9% iron and
30.1% dioxygen by mass [Atomic mass of Fe = 55.85, O = 16]
Ans : Fe
2O
3

46. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES
SOME BASIC CONCEPTS OF CHEMISTRY
46. A gaseous compound contains 1.59% hydrogen, 76.09% oxygen and 22.32%
nitrogen by weight. 0.939 g of the compound occupies 333.4 ml at STP. What is the
molecular formula of the compound?
Ans : HNO
3

47. I C S E, C B S E, I S C AND UP BOARD + FOUNDATION CLASSES