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Miscellaneous Exercises - I
Exercise 1: State, whether the following statements are True or False?
(i) ΔHfusion = ΔHsub – ΔHvap
(ii) Bond formation is always exothermic
(iii) Enthalpy of neutralisation of NH4OH with HCl is higher than enthalpy of NaOH with HCl.
(iv) Heat of reaction is independent of temperature.
(v) Heat of combustion of a fuel = caloric value of fuel
Exercise 2: A solution of 5 gm of Haemoglobin (molecular weight = 64000) in 100 cc of solution shows a temperature raise of for complete oxygenation. Each mole of haemoglobin binds 4 mole of oxygen. If the heat capacity of the solution is calculate per gm mole of oxygen bond.
Exercise 3: At 25oC, the enthalpy change for the reaction
H2SO4 + 5H2O = H2SO4.5H2O (all liquids) is -580.32 kJ / mole. Calculate the temperature change if 1 mole of is dropped into 5 mole of Assume no heat loss to the surroundings and that the specific heat capacity of solution is 4.184 Jk–1 g–1
Exercise 4: The for the neutralisation reaction
Compute C2H6(q) for the reaction CO2
Exercise 5: The. The first and second ionization energies of Ca are 590 and 1145 kJ / mole. The enthalpy of formation of Ca is 178 kJ / mol. The bond enthalpy of is 193 kJ / mole and enthalpy of vapourisation of is 31 kJ / mole. The electron affinity of Br(g) is 325 kJ / mole. Calculate the lattice energy of CaBr2(s).
Exercise 6: The heats of combustion of yellow phosphorus and red phosphorous are –9.19 kJ and – 8.78 kJ respectively, and then calculate the heat of transition of yellow phosphorus to red phosphorous.
Exercise 7: Calculate the enthalpy change when infinitely dilute solutions of CaCl2 and Na2CO3 mixed for Ca2+ (aq), (aq) and CaCO3(s) are – 129.80, – 161.65, – 288.5 kcal mole–1respectively.
Exercise 8: Calculate the heat of formation of ethyl acetate from ethyl alcohol and acetic acid. Given that heat of combustion of ethyl alcohol is 34 kcal and of acetic acid, it is 21 kcal and of ethyl acetate, it is 55.4 kcal.
Exercise 9: For the given heat of reaction,
(i) C(s) + O2(g) = CO2(g) + 97 kcal
(ii) CO2(g) + C(s) = 2CO(g) – 39 kcal
Calculate the heat of combustion of CO(g).
Exercise 10: 1 mole of an ideal gas undergoes reversible isothermal expansion from an initial volume V1 to a final volume 10V1 and does 10 KJ of work. The initial pressure was 1 × 107 Pa.
(i) Calculate V1
(i) If there were 2 mole of gas, what must its temperature have been?
Answer to Miscellaneous Exercises
Exercise 1: (i) True
Exercise 2: -41.47 kJ
Exercise 3: 73.7oC
Exercise 4: 14.0 kJ / mol
Exercise 5: -2162 kJ / mole
Exercise 6: (i) P4 (yellow) +5O2(g) ——> P4O10 + 9.19 kJ
(ii) P4(red) + 5O2(g) ——> P4O10 + 8.78 kJ
subtracting, P4(yellow) – P4 (red) = 1.13 kJ
=> P4(yellow) = P4(red) + 1.13 kJ
So, heat of transition of yellow to red phosphorus is – 1.13 kJ
Exercise 7: On mixing CaCl2 (aq) and Na2CO3
CaCl2 + Na2CO3 ——> CaCO3¯ + 2NaCl
Solutions are very dilute and thus 100% dissociation occurs
Ca2+(aq)+2Cl-(aq)+2Na+ (aq) + (aq) —> CaCO3¯ + 2Na+(aq) +2Cl-(aq) or Ca2+(aq)+ + CO32– (aq) —> CaCO3(s)
ΔH = ΣH°products – ΣH°reactants
or ΔH =
ΔH° of a compound = ΔH° formation = –288.5 – (–129.8 – 161.65)
= 2.95 kcal/mole
Exercise 8: -400 cals
Exercise 9: Subtracting equation (ii) from equation (i), we get
C(s) + O2(g) = CO2(g) + 97 kcal
CO2(g) + C(s) = 2CO(g) – 39 kcal
or, –CO2(g) + O2(g) = CO2(g) – 2CO(g) + 136 kcal
or, 2CO(g) + O2 = 2CO2(g) + 136 kcal
or, CO(g) + 1/2 O2(g) = CO2(g) + 68 kcal
Required value = 68 kcal
Exercise 10: (i) 4.34 × 10–4 m3
(ii) 261.13 K