assignment level questions

7/28/2019 Assignment Level Questions

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Assignment Level-I1) .

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 02molecules 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 inone 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


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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. C6H12

8. 90g & O2 is limiting agent

9. 7

11. 10^3 g-atoms

12. 2.69 x 10^10 moleclues

13. 28.02gNote: (^)-stands for raise to the power. (A)-angstronm

Assignment Level-II1.A complex of iron contains 45.6% iron by mass. Find out the number of iron atomsin 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. Calculatethe 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.


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(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 20 = 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 endof this sentence has a mass of about one microgram. Assumingthat 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 NO2 in 100g of mixture.

(IIT - 1979)Note: (^)-stands for raise to the power. (A)-angstronm

Answers-II1. 2.45 x 10^22

2. C3 H5O2

3. C2H8Br24. C 6H8N2

5. FeSO4.7H2O

6. N14-99.33% , N15-0.7%

7. 28.085amu8. 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 10^4amu14. 5 x 10^16 atoms 15. 0.437


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