FIITJCC RANKERS STUDY MATERIAL

IIT-JEE, 2002

PHASE -1

CHEMISTRY

Time: Two Hours Maximum Marks : 100

Note: i) There are NINE questions in this paper. Attempt ALL questions.

ii) Answer each question starting on a new page. The corresponding question number must be written in the left margin. Answer all parts of a question at one place only.

iii) Use of Logarithmic tables is permitted.

iv) Use of calculator is NOT PERMITTED

Useful Data:

Gas Constant R = 8.314 J mol"1K"1

= 0.0821 lit atm mol"1 K"1

= 2 Cal mol"1

Avogadro's Number N = 6.023 x 1023

Planck's constant h = 6.625 x 10"34 J sec. Velocity of light c = 3 x 108 m sec"1

1 electron volt ev = 1.6 x 10"19 J F = 96500 C

Atomic Masses Ag = 108, Mn = 55, Cr = 52, Ca CI = 35.5, N = 14, S = 32, Na = 2

40, C = 12, O = 16, K = 39, 4, S = 32, Na = 23, H = 1, P = 31, I = 127, As = 75,

Fe = 56, Ag = 108

Name of the Candidate

Enrollment Number

(F!ITJ€€ ICES House, Sarvapriya Vihur (Near Hauz Khas Term.), New Delhi - 16, Ph : 686 5182, 685 4102, Fax : 6513942

RSM12-P2-T(M)-CH-2

1. a) A 2.36 g sample of dolomite containing CaC03 and MgC03 were dissolved in 700 ml_ of decinormal solution of HCI. The solution was diluted to 2.5L and 25mL of this solution required 20 mL 0.01 N NaOH solution for complete neutralisation. Compute the composition of the ore. [7]

b) A sample of hydrazine sulphate (N2H6S04) was dissolved in 100 mL water 10mL of this solution was reacted with excess FeCI3 solution and warmed to complete the reaction. Ferrous ion formed was estimated and it required 20 ml of M/50 KMn04 solution. Estimate the amount of sulfate in one litre of solution. [7]

2. A mixture contains NaCI and an unknown chloride MCI.

i) 1 g of this is dissolved in water. Excess of acidified AgN03 solution is added to it. 2.567 g of a white precipitate is formed.

ii) 1 g of the original mixture is heated to 300°C. Some vapours come out which are absorbed in acidified AgN03 solution. 1.341 g of a white precipitate is obtained. Find the molecular weight of the unknown chloride. [10]

3 a) 1.6 g of Pyrolusite ore was treated with 50cm3 of 1.0 N, oxalic acid and some sulfuric acid. The oxalic acid left undecomposed was raised to 250 cm3 in a flask. 25cm3 of this solution when titrated with 0.1N KMn04 required 32cm3 of the solution. Find out the percentage of pure Mn02 in the sample and also the percentage of available oxygen. [6]

b) A mixture of pure K2Cr207 and pure KMn04 weighing 0.561 g was treated with excess of Kl in acid medium. Iodine liberated required 100 mL of 0.15 N of hypo solution for exact oxidation. What is the percentage of each in the mixture? [8]

4. Consider the following two possibilities for electron transition in a hydrogen atom,pictured below.

i) The electron drops from the Bohr orbit n = 3 to the orbit n = 2, followed by the transition from n = 2 to n = 1

ii) The electron drops from the Bohr orbit n = 3 directly to the orbit n = 1

a) show that the sum of the energies for the transitions n = 3 n = 2 and n = 2 n = 1 is equal to the energy of transition n = 3 -> n = 1

\

n=1 n=2 n=3

b) Are either wavelength (or) the frequencies of the emitted photons additive in the same way as their energies? Explain? [5]

5. a) If uncertainties in the measurement of position and momentum are equal, calculate uncertainty in the measurement of velocity. [4]

b) What accelerating potential is needed to produce an electron beam with an effective wavelength of 0.090A? [4]

6. a) Calculate the percentage of 'free volume' available in 1 mol gaseous water at 1.00 atm and 100°C. Density of liquid water at 100°C is 0.958 g/mL [4]

b) At room temperature the following reactions proceed nearly to completion: 2NO + 0 2 » 2N02 > N204 the dimer N204 sdolidifies at 262K. a 250 mL flask and a 100 mL flask are separated by a stop cock. At 300K, the nitric oxide in the larger flask exerts a pressure of 1.053 atm

FIITJCC ICES House, Saruapriya Vihar (Near Hauz Khas Term.), New Delhi - 16, Ph : 686 5182, 685 4102, Fax : 6513942