Chemistry-73.Phase-2-Subjective

FACULTY TRAINING TEST PHASE - II CHEMISTRY Time: 2 Hours Maximum Marks: 100 Instructions: 1. This paper consists of ELEVEN QUESTIONS only. 2. Attempt ALL questions. 3. Use of Calculator is NOT PERMITTED Name : 00000000000000000 Subject : 00000000000 1. The average person can see the red colour imparted by the complex [Fe(SCN)]2+ to an aqueous solution if the conc. of the complex is 6  10–6M or greater. What minimum conc. of KSCN would be required to make it possible to detect 1 ppm (by mass) of Fe3+in a natural water sample. The instability constant for [Fe(SCN)]2+ Fe3+ + SCN– is 7.142  10–3. The density of natural water can be assumed to be 1 g/cc. 2. LiCl.3NH3(s) LiCl.NH3(s) + 2NH3(g) Kp = 0.11 atm–2 at 40°C. A 5 litre vessel contains 0.1 mole of LiCl.NH3. How many moles of NH3 should be added to the flask at this temperature to derive the backward reaction for completion. 3. Two buffers (x) and (y) of pH 4.0 and 6.0 respectively are prepared from acid HA and the slat NaA. Both the buffer are 0.5 M in HA. The total conc. of salt is two buffers is 5.05 m. What would be the pH of the solution obtained by mixing equal volumes of the two buffers. Also calculate the dissociation constant of the acid HA. 4. The solubility of sparingly soluble MF2 is 1  10–2 mole litre–1 in 0.5 MHF if Ka for HF is 2  10–2. Calculate Ksp for MF2. 5. In a solution of 0.04 M FeCl2, 0.02 M FeCl3 and 0.01M HCl, how large may be its pH without there being precipitation of either Fe(OH)2 or Fe(OH)3? Ksp of Fe(OH)2 and of Fe(OH)3 are 8  10–16 and 4  10–28, respectively. 6. For the consecutive chain reaction A B C. Assuming that before the decomposition of A, there was no B & C in the consecutive chain reaction, then for k,  k2 show that [C] = [A]0 and why [C]  [A]0 ? 7. For the hypothetical reaction A  B, the rate is defined as = k[A]–1 a) Find the concentration A, after the running of 1 – hour of the reaction, given that K = 1.5 mol2 lit–2 sec–1. [A]0 = 100 moles b) Find the time required for the concentration fall to 10% of the initial value c) Does this reaction ever reach completion? If yes, how much time it needs for completion? 8. For the following parallel chain reaction’ the value of overall rate constant is 1.5  10–3 sec–1, whereas the value of the rate constant of I & II parallel path is 20% and 30% of the reaction. Given that the molar ratio of A:B, A:C and A:D are 1:1, 2:1 and 3:1 then find out the overall rate of consumption of A, given that concentration A = 10 mole/L. 9. Find the pH of the solution containing 11.4g of potassium alum KAl(SO4)2.12H2O is 0.1 dm–3 of solution. Assume the complete dissociation of the salt. K2(H2SO4) = 1.26  10–2 mol dm–3 Kh1(Al3+) = 1.4  10–4 mol dem–3 10. An indicator HIn has a standard ionization constant of 9  10–9. the acid colour of the indicator is yellow and the alkaline colour is red. The yellow colour is visible when the ratio of yellow form to red from is 30 to 1 and the red colour is predominant when the ratio of red form to yellow form is 2 to 1. What is the pH range of the indicator? 11. A sample of , as iodide ion was administered to a patient in a carrier consisting of 0.1 mg of stable iodide ion. After 4 days, 67.7% of the initial radioactivity in the thyroid gland of the patient. What mass percent of the stable iodide ion had migrated to the thyroid gland of the patient? [t1/2 of I - 131 = 8 days]

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