12. The following shows radioactive chemical reaction. Find out x, y and z in th

Question

12. The following shows radioactive chemical reaction. Find out x, y and z in the reaction. a) 239 on Pu Kr 2 n 36 239 133 98 Sb Y zan. 51' 13. Vapor pressure of naphthalene (C10H10) solution in ethanol (C2H5OH) is 43.5 torr at 20 oC. If normal vapor pressure of pure ethanol is 44.6 torr at 20 °C, a) Calculate mole fraction of naphthalene in this solution. b) By converting mole fraction to molality, find out the boiling point of this solution. (Kb of ethanol is 1.07 °C/m) 14. The following shows some reactions and their equilibrium constants. 10 N2(g) O2 (g) 2NO(g) Kc 1.5 x 10 2SO2(g) O2 (g) 2SO3(g) Kp 2.5 x 10 Using given information, calculate Ke of the following reaction. NO(g) SO2(g) ViN2(g) SO3(g) 15. The following shows titration reaction of 0.01 M 100 ml pyridine (CsHsN) with 0.05 M sulfuric acid (H2So4). a) Calculate pH when 5 ml of sulfuric acid is added to pyridine solution. b) Find out when the equivalence point will be reached and calculate pH at the equivalence point. (Consider that sulfuric acid is a strong enough acid and both protons will completely react with pyridine) c) What will be the best indicator for this titration? Choose from indicators below. Color Transition Range Color Transition Range Indicator name Indicator name Thymol Blue I-3 Brom thymol Blue 6-75 Methyl Orange 3-5 Phenolphthalein 8-9.5 Bromcerol Green 4-5.5 Alizarian Yellow R 10-12.5

Explanation / Answer

12) The equation should be balanced with respect to atomic number and mass number

a) total atomic number sum on reactants side = 94 + 0 = 94 = should be equal to = sum of products

94 = 36 + y

so y = 58

sum of mass number on reactants side = 239 +1 = 240 = should be equal to mass number of products

240 = 94 + x + 2

x = 144

so the element is Z = Ce

b) total atomic number sum on reactants side = 92 + 0 = 92 = should be equal to = sum of products

92 = 51 + x

so x = 41 so Y =Nb

sum of mass number on reactants side = 239 +1 = 240 = should be equal to mass number of products

240 = 133 + 98 + z X 1

z = 9

13)

a) Use Raoult's Law:

Psolution = (solvent) (P°solvent)

43.5 = (x) (44.6)

x = 0.97533 (this is the solvent mole fraction)

solute = 1 - 0.97533 = 0.02467

b) molality = moles of naphthalene / kg of solvent

Let total moles of solution = 1

so moles of solute = 0.02467 moles

moles of water = 0.97533

1 mole of water = 18grams

so 0.97533 moles = 18 X 0.97533 grams = 17.556 grams

So molality = moles of solute / mass of water = 0.02467 X 1000 / 17.556 = 1.405 molal.

normal boiling point of water = 100 0C

Elevation in boiling point = Kb x molality = 1.07 X 1.405

elevation = 1.5034 0C

So boiling point = 100+1.5034 0C = 101.5034 0C

14) N2(g) + O2(g) --> 2NO (g) Kc = 1.5 X 10^-10 .........1

Kp = Kc(RT)delta n

Here delta n = 2-2 = 0

so Kc =Kp

2SO2 + O2 --> 2SO3    Kp = 2.5 X 10^-9 .............................2

NO + SO2 --> 1/2N2 + SO3   Kc = ?

Let us calculate the Kp of the reaction by combining the equation 1 and 2

divide equation 2 by 2 and substract half of equation 1 from it.

2SO2 + O2 --> 2SO3 ] 1/2

-[N2(g) + O2(g) --> 2NO (g) ] 1/2

................................................

SO2 + NO --> SO3 + 1/2N2 ( the desired equation)

so the new kp will be = (Kp of equation 2 / Kp of equation 1)1/2 =( 2.5 X 10^-9 / 1.5 X 10^-10)1/2

New Kp = 4.08

now we know that

Kp = Kc(RT)delta n

R = 0.0821 ; T = 298 K delta n =1.5-2 = -0.5

so Kc = Kp (RT)1/2 = 4.08 (0.0821 X 298)1/2 = 4.08 X 4.94 = 20.1552

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