Previous IIT-JEE mole concept questions

Blazing goIITian

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14 May 2007 10:07:42 IST
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Previous IIT-JEE mole concept questions
Engineering Entrance , JEE Main , JEE Main & Advanced , Chemistry , Physical Chemistry , academic
Previous iit-jee mole concept questions
 
Assignment Level-I
1)     .
a)     Calculate the mass of 5 gram atoms of calcium. Atomic mass of alcium is 40.
b)      Calculate the mass of 1.5 gram molecules of water.
2)     Calculate the number of gram atoms and gram molecules in 25.4 mg of iodine (12). Atomic mass of I = 127 amu.
3)     How much sulphuric acid (H2SO4) can be obtained from 5 kg of pure sulphur (S8).
4)     What is the molar volume of water at 273 K. Density of water = 1.00 gm/ cm^3.
5)      6.02 x 10^20 molecules of a substance weigh 44 mg. What is the molecular mass of the substance.
6)     Two flask A and B of equal capacity contain lOg of oxygen and ozone respectively, under similar conditions. Wilch flask will have more number of 0 atoms and which one will have more number of molecules.
7)     A hydrocarbon contains 85.7% C. If 42 mg of the compound contains 3.01 x 10^20 molecules. What is the molecular formula of the compound.
8)     80 g of H2 are reacted with 80g Of 0 2 to form water find out the mass of water obtained. Which substance is the limiting reagent.
9)     15 gm of a compound Na2SO4. xH20 contains 2.36 x 10^23 H20 molecules. Find out the value of x.
10)Aluminium carbide contains 75% of Al. Aluminium oxide contains 52.9% of Al and C02 contains 27.27% of C. Show that these figures illustrate the law of reciprocal proportion.
11)Weight of one atom of an element is 6.644 x 10^-23 g. Calculate g atom of element in 40 kg.
(IIT - 1975)
12)O2 is present in a litre flask at a pressure of 7.6 x 10 ^10 mm of Hg. Calculate number Of 02 molecules in the flask at 0C.
(IIT - 1983)
13)It was found that 380 ml of a gas at 27C and 800 mm of Hg was weighed 0.455 g. Find out molecular weight of gas
(IIT - 1975)
14)Carbon forms two gaseous oxides. One of these oxides contain 42.8% carbon. While the other contains 27.27% carbon. Explain which of the laws of chemical combination this data illustrates. State the law.
15)Hydrogen and oxygen are known to form two compounds. The hydrogen content in one of these is 5.93%. While in the other it is 11.2%. Show that this data illustrates the law of multiple proportion.
Note: (^)-stands for raise to the power. (A)-angstronm
 
 
                                   Answers-I
1.(a) 200g ; (b)27g
2. 2 x 10^-4 g-atoms ; 1 x 10^-4 g-atoms
3. 15.312Kg
4. 18cc
5. 44g
6. The no. fo oxygen atoms will be same.But A will have more no. of molecules.
7. C6H 12
8. 90g & O2 is limiting agent
9. 7
11. 10^3 g-atoms
12. 2.69 x 10^10 moleclues
13. 28.02g
Note: (^)-stands for raise to the power. (A)-angstronm
 

Assignment Level-II
1.A complex of iron contains 45.6% iron by mass. Find out the number of iron atoms in 5.00 gm of this complex.
2.An organic compound on analysis is found to have th-e following compos't' i ions: C = 41.4%, H=5.75%, N = 16.081% and rest is oxygen find out the empirical formula of the Compound.
3.An organic compound has the following percentage composition, C = 12.36%, H = 2. 13%, Br = 85%. Its vapour density is 94. Find its molecular formula.
4. A compound of carbon, hydrogen and nitrogen contains these elements in the respective ratio 9:1:3:5. Calculate the empirical formula. If the molecular weight is 108, what is its molecular formula?
5. 1. 00 g of a hydrated salt contains 0.2014 g of iron, 0. 1153 g of sulphur, 0.2301 g of oxygen and 0.4532 g. of water of crystrallisation find the empirical formula. (Fe = 56, S = 32, 0=16).
6. Nitrogen occurs in nature in the form of two isotopes with atomic mass 14 and 15 respectively. If average atomic mass of nitrogen is 14.0067. What is the percentage abundance of the two isotopes.
7. The relative abundance of various isotopes of silicon is as : Si - 28 = 92.23%, Si - 29 = 4.67 % Si-30 = 3. 10%. What is the average atomic mass of silicon.
8. An impure sample of sodium chloride which weighed 0.50 g gave on treatment with excess of silver nitrate solution, 0.90 g of silver chloride as precipitate. Calculate the percentage purity of the sample.
9.
(a) A hydrated sulphate of a divalent metal (atomic weight 24) contains 51.22% water of crystallisation. Calculate the number of molecules of water of crystalisation of the hvdrated salt.
(b) A sample of Epsom salt, MgSO4. 7H20 was found to contain, on analysis, 7.32% of Mg. Calculate the percentage purity of the sample (Atomic weight H = 1, 0 = 16,Mg=24, S = 32)
(c) Which of the following compounds has the higher percentage of nitrogen. Ca(NO 3)2; CaCN2; (NH4)2SO4. (H = 1 , C = 12, N = 14, 0 = 16, Ca = 40)
10. A crystalline salt is mixed with sand and gives on analysis the following results -, Cu = 22.905 %-, S= 11.52% 0 = 23.085%' H 2 0 = 32.463% and the rest sand. Determine the percentage composition of the crystalline salt and deduce its molecular formula ( Cu = 53. 5, S = 32)
11. A certain compound containing only carbon and oxygen has a approximate molecular weight of 290. On analysis it is found to contain exactly 50% by weight of each element. What is the molecular formula of the compound.
12. How many iron atoms are present in a stainless steel ball bearing having a radius of 0. 1 inch (1 inch = 2.54 cm). The stainless steel contains 85.6% Fe, by weight and has a density of 7.75 g / CC.
13. A sample of potato starch was ground in a ball mill to give a strach like molecule of lower molecular weight. The product analysed 0.086% phosphorus. If each molecule is assumed to contain one atoi-n of phosphorus, what is the molecular weight of the material.
14. The dot at the end of this sentence has a mass of about one microgram. Assuming that the black stuff is carbon, calculate the approximate number of atoms of carbon needed to make such a dot (1 microgram = 1 x 10^-6 g).
15. The vapour density of a mixture containing NO2 and N2O4 is 38.3 at 27C, Calculate the moles of NO 2 in 100g of mixture.
(IIT - 1979)
Note: (^)-stands for raise to the power. (A)-angstronm
 
 
Answers-II
1. 2.45 x 10^22
2. C3 H5O2
3. C2H8Br2
4. C 6H8N2
5. FeSO4.7H2O
6. N14-99.33% , N15-0.7%
7. 28.085amu
8. 73.38%
9. (a)7H2 O (b)75% (c)Ca(OH)2 ;35%
10. Cu=28.45% , S=12.82% , O=25.5% , H2O=36.07%
11. C12O9
12. 4.91 x 10^21
13. 3.6 x 10^4amu
14. 5 x 10^16 atoms
15. 0.437
Note: (^)-stands for raise to the power. (A)-angstronm


Comments (2)


New kid on the Block

Joined: 4 Apr 2013 16:41:59 IST
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4 Apr 2013 16:59:31 IST
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it is very helpful to me

New kid on the Block

Joined: 31 Mar 2013 10:08:04 IST
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4 Apr 2013 19:29:12 IST
0 people liked this

very helpful...for goiitians



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