Thermo Chemistry
Thermo Chemistry
Thermo Chemistry
ABOUT EDUCATORS
PIYUSH MAHESHWARI
• BE (Hons.)
• 11 year experience of IIT JEE in InorganicChemistry
• Author of 'Super Problems in Inorganic Chemistry',
• Ex. HOD Bansal Classes, Kota
• Ex. Senior Faculty of Vibrant Academy, Kota and Allen Career Institute, Kota
BRIJESH JINDAL
• BTech Jaipur MNIT
• 11 year experience of IIT JEE in Physical Chemistry
• Ex. Senior Faculty of Vibrant Academy, Kota, Allen Career Institute, Kota and Bansal
Classes, Kota
THERMOCHEMISTRY
r y E : 3
Sr(s)E
r y
1
+ O (g) SrO(s) H° = – 600 kJ/mol
i s t
i t
s SrO(s) + CO (g) SrCO (s) H° = – 200 kJ/mol
2 2
e m
m C(graphite) + O (g) CO (g) H° = – 400h
e C
2 3
C h 2 kJ/mol 2
s
1
s
SO2(g) +
r t
O SO3(g)
2 2
e t
H° = – 100 kJ/mol
r
SO (g) + H e p
x p O(l) H SO (aq)
3 2 H° = – 230 kJ/mol
2 4
E x
H = –y
r EkJ/mol 0
t r y
f
i st
300
SO 2 (g ) H (H O ) = – 170 kJ/mol f
i s 2 (l )
e m h ise
m
Chformation, of C H (g) . Given H for CO (g) & H O (l)Care 395 & 286 kJ respectively.
Q.3 When 2 moles of C H (g) are completely burnt 3120 kJ of heat
2 6 liberated . Calculate the enthalpy of
2 6 f 2 2 - -
Q.4 Calculate standard enthalpies of formation of carbondisulphide (l) . Given the standard enthalpy of
r ts
combustion of carbon (s) , sulphur (s) & carbondisulphide (l) are : 393.4, 293.3 and
ts
e r
xp pe
1108 kJ mol 1 respectively.
r y E E x
Q.5
st y
From the following data at 25°C, Calculate the standard enthalpy of formation of FeO(s) and of Fe2O3(s).
i tr
e mReaction
i s
H (kJ/mol) o
m
r
h
C (ii) FeO (s) + C(graphite) Fe(s) + CO(g) Ch155.5
(i) Fe O (s) + 3C(graphite) 2Fe (s) + 3CO(g)
2 3 e
492.5
is t
Calculate H for the reaction
x
m ClF(g) + F2(g) ClF3(g)
e the following data : ryE
C h i s t
H = 92 kJ em
Q.7 Given
Ch
2NH3(g) N2(g) + 3H2(g)
2H2(g) + O2(g) 2H2O(g) H = – 48 kJ
Calculate H for the reaction :
2N2(g) + 6H2O(g) 3O2(g) + 4NH3(g)
Page # 1
THERMOCHEMISTRY
The enthalpy change for the reaction C3H8(g) + H2(g) C2H6(g) + CH4(g) at 25º C is
s
Q.8
r t
55.8 kJ/mol. Calculate the enthalpy of combustion of C2H6(g). The enthalpy of combustion of
e r ts x
H2, & CH4 are 285.8 & 890.0 kJ/mol respectively. Enthalpy of combustion of propane is pe
2220 kJ mol1.
x p r y E
r E
y enthalpies of formation of C H COOH(s), i t
sCO (g) & H O (l) are
Q.9
i
At 300 K, the t
s& –286 kJ mol respectively .
standard
e m
6 5 2 2
m
– 408, – 393
e
–1
Q.10
ts r ts
Calculate the mass of mercury which can be liberated from HgO at 27º C by the treatment of excess
r pe
HgO with 45.4 kJ of heat at :
(a) constant pressure
p e
(b) constant volume
x
E x
Given : Hfº (HgO, s) = 90.8 kJ mol1 &
y
M (Hg) = 200.6 g mol1 . E
r y tr
i stthat on combustion of 5.6 gm of but - 1-ene(g), 70Kcalmofisheat is liberated in a closed
Q.11 It is observed
C
rigid combustion
r t s
Given : CH° (C4H4(g)) = 22340 kJ/mol
CH° (C4H8(g)) = 2286 kJ/mol
CH° (H2(g)) = 22755 kJ/mol
ts
e r
p complete combustion, the following enthalpy values are obtained
e:
x
E(g) + O (g) 2H O(g) H = – 242 kJ/mol
Q.13 When hydrogen gas undergoes
x p
r y
t 2H (g) + O (g) 2H O(l) H = – 286 kJ/mol try
2H
E
s
2 2 2
m i 2 2 2
i s
h e
Calculate H for H O(l) H O(g)
2 2
e m
C Compound
Q.14 Three isomers with formula C H their enthalpy
4 8
H(kJ/mol)
of
C h
combustion data is given as :
C
cis-2-butene – 2687.5
tras-2-butene – 2684.2
1-butene –2696.2
r t s
What is the enthalpy change for conversion of cis-2-butene to trans-2-butene?
x p find the
e m r y E
h t
s of hydration of Ag (g)
Q.16 The lattice enthalpy of AgF is 958 kJ/mol and AgCl is 905 kJ/mol. Theienthalpy
C is – 446 kJ/mol, that of F is – 506 kJ/mol and that of Cl (g) ise–m +
– – 364 kJ/mol. Calculate the H of
Ch
sol
AgCl(s) and AgF(s).
Q.17 The enthalpy of solution of anhydrous CuSO4 is – 15.9 kCal and that of CuSO4.5H2O is 2.8 kCal.
Calculate the enthalpy of hydration of CuSO4. Page # 2
THERMOCHEMISTRY
The enthalpies of neutralization of NaOH & NH4OH by HCl are 13680 Cal and 12270 Cal
s
Q.18
r t
s pe
respectively . What would be the enthalpy change if one gram equivalent of NaOH is added to one gram
e r t x
equivalent of NH4Cl in solution ? Assume that NH4OH and NaCl are quantitatively obtained.
p
x following reactions r yE
E
y (g) — CO(g) ; H = –110 kJ
Q.19 From the data of H of the
r
C(s) +t1/2O i s t
i s+ H O(g) — CO(g) + H (g) ; H = 130 kJ hem
2
and
h e m C(s)
Calculate the mole composition of the mixture of steamC
2 2
and oxygen on being passed over coke at
C1273 K, keeping the reaction temperature constant and their is no heat exchange with surrounding.
Q.20 The polymerisation of ethylene to linear polyethylene is represented by the reaction
ts r ts
r pe
nCH2 = CH2 (–CH2 CH2–)n
p e x
where n has a large integral value . Given that the average enthalpies of bond dissociation for C=C &
E x y E
CC at 298 K are 590 & + 331 kJ mol1 respectively. Calculate the enthalpy of polymerisation
tr y
per mole of ethylene at 298 K .
i s tr
Q.21 Them
i s
enthalpies of neutralization of a weak acid HA & e am
e h weak acid HB by NaOH are
Ch 6900 Cal/equivalent & 2900 Cal/equivalent respectivelyC. When one equivalent of NaOH is added
to a solution containing one equivalent of HA & one equivalent of HB, the enthalpy change was
3900 Calories . In what ratio is the base distributed between HA & HB ?
r tsBOND ENTHALPY ts
Q.22 Using bond enthalpy data,p e enthalpy of formation of isoprene. Neglect resonance in isoprene.
e r
x calculate
E + 4 H (g) H C = C| — C| = CH (g)
5yC(s) x p
st r 2 2 2
r y E
m i CH H
i s t
h e 3
e m
C Given : C H = 98.5 k Cal ;
C C = 83 k Cal ;
h
H H = 104 k Cal
Ck Cal &
C = C = 147
;
Q.23 The enthalpy of atomization of PH3 is 954 kJ mol–1 and that of P2H4 is 1.485 M J mol–1. What is the
r
bond enthalpy of the P–P bond?t s
p e
E x r ts
(g)y C H (g) e
Q.24 Using the bond enthalpy data given below, calculate the enthalpy change for the reaction.
C H (g) + H r
Data: is
2 4 t 2 2 6
x p
e m C–H ry
E
hBond C–C
C Bond Enthalpy 337 kJ/mol 606 kJ/mol e410.4
C=C
s t H–H
ikJ/mol 431.8 kJ/mol
m
Ch
Page # 3
THERMOCHEMISTRY
Q.25 Compute the enthalpy of formation of liquid methyl alcohol 1
in kJ mol , using the following data.
Enthalpy of vaporisation of liquid CH3OH = 38 kJ/ mol .
r ts
r ts
Enthalpy of formation of gaseous atoms from the elements in their standard states are
e x pe
p E
x try
H 218 kJ / mol ; C 715 kJ / mol ; O 249 kJ / mol.
E s
try
Average Bond energies
s
C H 415 kJ / mol ;
mi
C O 356 kJ / mol ; O H 463 kJ / mol
i e
e m
h of formation of CH CN = 90 kJ/mol
Q.26 From the following data :
Ch
CEnthalpy
Enthalpy of formation of C2H6 = – 85 kJ/mol
3
x p er x pe
C–H bond enthalpy = 415 kJ/mol
y E r y E
Calculate the bond enthalpy of (i) C – C ; (ii) C N
r
stof combustion of acetylene is –312 kCal per mole. If enthalpy
i t
sof formation of CO &
i m
Om e
Q.27 The enthalpy
He are 94.5 & 68 kCal per mole respectively, calculate Ch
2
ChGiven that enthalpy of atomisation of C is 150 kCal per moleCand H – H bond enthalpy and C – H bond
2 C bond enthalpy.
enthalpy are 103 kCal per mole and 93.50 kCal per mole respectively.
Q.28
r ts
Using the given data calculate enthalpy of formation of acetone (g) . [All values in kJ mol1]
ts
bond enthalpy of :
e r
C H = 415 ;
E xp
C C = 345 ; (C = O) = 728.0 ;
x pe
r y
(O = O) = 495.0 ; H H = 436 ;
E
subH of C = 720
y
Q.29 Find the i
st i s tr
e m enthalpy of S–S bond from the following data.
m
C h(i) C H – S – C H (g)
h e
H = – 147 kJ/mol
C
2 5 2 5 f
(ii) C H – S – S – C H (g)
2 5 2 H = – 202 kJ/mol
5 f
xpe
CH3CH2OH(g) + 3O2(g) 2CO2(g) + 3H2O(g)
ts
E
[Given : Bond energy (C – H) = 412 kJ/mol ; (C = O) = 743 kJ/mol
r y
(C – C) = 348 kJ/mol ; (C – O) = 360 kJ/mol
per
is t
(O = O) = 496 kJ/mol ; (O – H) = 463 kJ/mol
x
e m ryE
h
C Calculate resonance energy of CO from the following data. emis
RESONANCE ENERGY t
Q.31
h
2(g)
H of CO = –280 kJ / mol H CO = –120 kJ/mol
H OC
combustion f
H of C
atomisation = 720 kJ / mol
(graphite) = O = 500 kJ molBE
–1
H C = O = 710 kJ /mol BE
Page # 4
THERMOCHEMISTRY
s
Q.32 Calculate the enthalpy of combustion of methyl alcohol at 298 K from the following data
CH CO OH
r t
s pe
Bond O=O C=O
er
Bond Enthalpy(kJ mol1) 415 t 352 465 494
x
710
p E
x try
Resonance energy of CO2 = 143 kJ mol 1
E s
try
Latent heat of vaporisation of methyl alcohol = 35.5 kJ mol1.
s
Latent heat of vaporisation of water = 40.5 kJ mol1.
mi
i e
h e
Q.33 What
m
will be the value of resonance energy of N O if Ch
CH N = N = 400 kJ/mol ;
BDE H of
2
N O = 100 kJ mol
2
–1
r ts
The thermal capacity of Calorimeter system is 17.7 kJ K1 . (R =
3
J mol1 K1)
ts
e r
xp pe
Q.35 When 0.2 mol of ethane is burnt completely in a bomb calorimeter, the temperature of calorimeter
r y E E x
system increased by 2 K. What should be the increase in temperature of the same calorimeter system,
em
C U C 2 H 6 g
= – 400 Kcal/mol and C U CH 4 g
i s
Q.36 h
m
Two solutions initially at 25°C were mixed in an adiabatic constantepressure Calorimeter. One contains
h 100 ml of 0.80 M NaOH. After
C 400 ml of 0.2 M weak monoprotic acid solution. The otherCcontain
mixing temperature increased to 26.2 °C. How much heat is evolved in the neutralization of 1 mole of
acid? Assume density of solution 1.0 g/cm3, and specific heat of solution 4.0 J/g-K. Neglect heat capacity
of the Calorimeter.
r ts
Q.37
xpe
Benzoic acid is a common standard used in Bomb calorimeters, which maintain a constant volume. If
ts
E r
1.22 gm of benzoic acid gives off 31.7 J of energy when burned in the presence of just sufficient oxygen
y
tr pe
at an initial temperature of 24.6°C, calculate molar heat capacity at constant volume of final product
is x
em ryE
mixture if all the heat produce is used for increasing temperature of the final product mixture and the final
C h i s t
temperature is 49.6°C. Also calculate, w and U for the given amount, assuming ideal gas behaviour.
hem
C
Page # 5
THERMOCHEMISTRY
i s e m
m Ch H° = –176 kJ/mol
Find f H° for HCl(g) from the following data:
e
Q.2
Ch
NH3(g) + HCl(g) NH4Cl(s); r
N2(g) + 3H2(g) 2NH3(g); rH° = –92 kJ/mol
N2(g) + 4H2(g) + Cl2(g) 2NH4Cl(s); rH° = –629 kJ/mol
(A) 536.5 kJ/mol (B) –361 kJ/mol (C) –92.5 kJ/mol (D) None
ts r ts
Q.3
x p er
Calculate H combustion of acetone if H f of acetone = – 250 kJ
x pe
E yE
H combustion of Cgraphite = – 390 kJ/mol & H combustion of H2(g) = – 280 kJ/mol :
y r
s t r
(A) – 1230 kJ/mol (B) – 1760 kJ/mol
i s
(C) – 1370 kJ/molt (D) – 1410 kJ/mol
m i e m
Q.4
e
Calculate
h
C – H Bond energy from the following data :
C h
C (A) 1663.37 kJ (B) 415.84 kJ (C) 179.17 kJ (D) 74.81 kJ
H(C ) = 716.68 kJ/mol
f (g) H(H ) = 217.97 kJ/mol
f (g) H(CH ) = – 74.81 kJ/mol
f 4(g)
Q.5 Identify the options in which H > U. [Assume gases to behave as ideal]
r ts
(A) Polymerisation of ethene(gas) into polythene (gas).
ts
e r
xp
(B) H2O(g) H2(g) + O2(g)
(C) HCl(g) H2(g) + Cl2(g)
y E
(D) CH4(g) + O2(g) CO2(g) + H2O(l)
x pe
r
The reactiontCH (g) + Cl (g) CH Cl(g) + HCl(g) has H = –25 kCal. y
s r E
Q.6
m i 4 2 3
i s t
e Bond
m
Ch Bond Energy
kCal
C h e
84
C—Cl
H—Cl 109
C—H x
r ts Cl—Cl
p e y
E x x:y=9:5
r ts
(A) 70 kCal ry (D) 60 kCal pe
From the given data, what is the bond enthalpy of Cl—Cl bond
t
isinvolving gold have been of particular interest to a chemist . ConsiderytheEfollowing
(B) 80 kCal (C) 67.75 kCal
x reactions,
Q.7 m
e Au(OH) + 4 HCl HAuCl + 3 H O ,
Reactions
h H = s
r
28tkCal
C Au(OH) + 4 HBr HAuBr + 3 H O ,
3 4 2
m i
3 4 2
h eone mole of HAuBr was mixed with
H = 36.8 kCal
In an experiment there was an absorption of 0.44 kCal when
C
4 moles of HCl . What is the percentage conversion of HAuBr into HAuCl ?
4 4
4
h e m
(C) more than
C
second case by 11.4 kJ
Q.10CFind U° for the reaction 4HCl (g) + O (g) l 2Cl (g) + 2H O (g) at 300 K. Assume all gases are
r 2 2 2
ideal.
s
Given: H2(g) + Cl2(g) 2HCl (g)
t
o
r H 300
r ts
= – 184.5 kJ/mol
r
2H (g) + O (g) e2H O (g) p e
xp x
o
H = – 483 kJ/mol (Use R = 8.3 J/mol)
2 2
r y E
300
r
st : 2A + B
(C) –111.5 kJ/mol
t
(D) None
i s= 100 cal/K mol at 300K.
m i e m
h e
Q.11 For a reaction (g) C , U° = 30 Kcal/mol,
(g)
C h
S°
(g)
(D) – 10 Kcal
Q.12
r ts
The combustion 1.22g benzoic acid (M = 122) in a bomb calorimeter at 300K caused a temperature
ts
e
rise of 3K, while combustion of 0.88g ethyl ethanoate (M = 88) caused a temperature rise of 2K.
xp
Calculate the enthalpy change of combustion of CH3COOC2H5(l) at 300K.
per
r y E
Given : Internal energy change of combustion for benzoic acid = – 3000kJmol–1 at 300K
E x
i s t
(A) – 2000kJ (B) – 2002.49kJ (C) – 2006.5kJ
y
(D) – 3002.5kJ
t r
e m in nature. Each problem on an average requires 21 Joules of m
Q.13 In order to solve a complex physical chemistry problem, brain requires some is"neural energies" which are
Chamount e energy is obtained from oxidation
electrical neural energy. Calculate minimum
C h
of glucose required to solve 10 such problems if all electrical
of glucose.
1000
[Given : H combustion of glucose = – 2800 kJ/mole, Scombustion of glucose = – J/molK,
3
Temperature = 300K ]
r ts
(A) 14 gm
e
(B) 14 mg (C) 20 gm (D) 120 mg
p yield on combustion of hydrogen atoms to steam to the yield on combustion
E x r ts
r yof hydrogen molecules to steam?
Q.14 What is the ratio of the
t
enthalpy
p e
is
of an equal mass
m E x
h e : H (g) + O (g) H O(g) H = – 242 kJ istry
Given
1
C B.E. (H – H) = 436 kJ
2 2 2 2
e m
(A) 0.80 : 1 (B) 1 : 0.80 (C) 1.80C:1h (D) 2.80 : 1
Page # 7
THERMOCHEMISTRY
s
Q.15 The molar heat capacities at constant pressure (assume constant with respect to temperature) of A, B
and C are in ratio of 1.5 : 3.0 : 2.0 . If enthalpy change for the exothermic reaction A + 2B 3C at
r t
e r t s
300 K is – 10 kJ/mol & Cp,m (B) is 300 J/mol then enthalpy change at 310 K is :
x pe
(A) – 8.5 kJ/mol
x p
(B) 8.5 kJ/mol (C) – 11.5 kJ/mol
y E
(D) none of these
r
r E
yof solid NaCl is 772 kJmol and enthalpy of solution i t
s2 kJmol . If the hydration
enthalpy ofiNa
t
Q.16 The lattice enthalpy
e mof hydration of chloride ion?
s & Cl ions are in the ratio of 3:2.5, what is thehenthalpy
–1 is –1
(A)e
h m
–140 kJmol
+
–1
–
C
Q.17 H 0f of water is – 285.8 kJ mol–1. If enthalpy of neutralisation of monoacid strong base is
ts r ts
p er
–57.3 kJ mol–1, H 0f of OH– ion will be
p e
(A) – 228.5 kJ mol
x
(B) –1
228.5 kJ mol (C) 114.25–1
kJ mol (D)
E
–114.25 x
kJ mol –1 –1
r y E tr y
(A) H i
st
Q.18 Select the correct option.
i s
e m [H(g)] is equal to H of H (g)
h e m
h
f atomisation 2
r ts
H of of atomic B is 134.5 Kcal/mol and H of of atomic F is 118 Kcal/mol. H of of BF3(g) is
ts
e
Q.19
xp
– 271.5 Kcal /mol. Average B – F energy would be
per
ry E
(A) 97.7 Kcal / mol
x
(B) 116.6 Kcal / mol (C) 135.4 Kcal / mol (D) 253.3 Kcal / mol
E
st thermochemical equations:
Q.20 Study theifollowing try
e mA B ; H = + 100 Kcal i s
h em
C The correct order of enthalpies of formation of A, B and CCis h
B C ; H = – 80 Kcal
(A) A < B < C (B) A < C < B (C) C < A < B (D) B < C < A
Q.21
s
From following Born Haber cycle, identify incorrect statement :
r t
xpe 872 kJ
C(g) + 4H(g)
ts
yE r
r pe
C(g) + 2H2(g)
is t 715 kJ
x
em
Energy
C(graphite) + 2H2(g)
r y E
C h 75 kJ
i s t
em
CH4(g)
(A) fH(CH4) = – 75 kJ
(C) sublimationH of C = 715 kJ/mol
h
(B) Bond energy of (C–H) = 145 kJ/mol
(D) C H of H(g) = 218 kJ/mol
formation
s
Page # 8
THERMOCHEMISTRY
Q.22 Calculate enthalpy of combustion of propane [C3H8 (g)] in kJ/mol at 298 K.
Given : B.E.(O = O) = 498 kJ/mol ; B.E. (C = O) = 804 kJ/mol
r ts
B.E. (C–H) = 410 kJ/mol
er ts ; B.E.(O–H) = 464 kJ/mol
x pe
B.E. (C–C) = 345 kJ/mol
p ; Resosnace energy of CO2(g) = – 143 kJ/mol
E
x try
Hvaporization (H2O, l ) = 41 kJ/mol
E s
try i
(A) –1996 (B) –2669 (C) –2324 (D) None of these
i e mcompound?
sfollowing represent standard formation reaction ofhgiven
h m
Q.23 Which of the
e C 1
C (A) Ag (aq) + Cl (aq) AgCl(s)
+ – (B) CO(g) + O (g) CO (g)
2 2 2
1
(C) H (g) + (aq) H+(aq) + 1e– (D) 2H2(g) + O2(g) 2H2O(l)
2 2
t s r ts
p e r p e
Q.24 0.2 M, 100 ml NaOH is mixed
x
with
E x
0.4 M, 100 ml HCl solution. Determine energy released during the
Given : HE
reaction.
r y (B) 1150 kJ
(aq) + OH¯ (aq) H O (l) r y
t2300 kJ
H = – 57.5 kJ
s
+ –1
m i (C) 2300 J
e m (D)
Q.25 h e C h
C HCl
Enthalpy of neutralization of H PO acid is –106.68 kJ/mol using NaOH. If enthalpy of neutralization of
r ts
e is mixed with 300 ml 0.1 M HCl then increase in temperatureerists
Q.26 When 100 ml 0.2 M KOH is mixed with 100 ml 0.2 M HCl, temperature of solution increases by t1oC
while when 300 ml 0.1 Mp
E x KOH
x p t o2C
t r y (B) t > t
then which one is correct.(Assuming
y E
density as well as specific heat of final solutions are same)
(A) t = t
1
i s 2 1 (C) t < t
2 1 2
i s r
(D) Can't be
t
predicted
e m m
h
–1
(in kJ) when 0.5 mole of H SO react with 0.75 mole of NaOH iseequal to
Q.27 The enthalpy of neutralisation of HCl and NaOH is –57 kJ mol . The heat evolved at constant pressure
C
(A) 57 ×
3
2
(B) 57 × 0.5
4
Ch
(C) 57 (D) 57 × 0.25
4
More than one may correct
Q.28 From the following data at 25°C
r ts
1
Reaction
1
xpe rH° kJ/mol
ts
E
H (g) + O2(g) OH (g)
y
42
r
r pe
2 2 2
is 1 t x
em
H2(g) + O2(g) H2O(g)
2
–242
ryE
C h H2(g) 2H(g) 436
i s t
O2(g) 2O(g) 495
hem
C
Which of the following statement(s) is/are correct :
(A) rH° for the reaction H2O (g) 2H(g) + O(g) is 925.5 kJ/mol
(B) rH° for the reaction OH(g) H(g) + O(g) is 502 kJ/mol
(C) Enthalpy of formation of H(g) is –218 kJ/mol Page # 9
(D) Enthalpy of formation of OH(g) is 42 kJ/mol
THERMOCHEMISTRY
r t
ts (B) H (g) + Cl (g) 2HCl x pe
1 1
(A)
2
H2(g) +
2
p e r
Br2(g) HBr 2 2
y E
NH (g) + Cl (g)
r
– NH Cl(s)
i s t
st representing H of C (graphite). hem
4 4 4 2 4 10
(E)
m i
Reaction combustion
Q.31 100 ml 0.25 M H2SO4 (strong acid) is neutralised with 200 ml 0.2M NH4OH in a constant pressure
ts r ts
r pe
Calorimeter which results in temperature rise of 1.4 °C. If heat capacity of Calorimeter content is
p e
1.5 kJ/°C. Which statement is/are correct
x
x E
E try
Given : HCl + NaOH NaCl + H2O + 57 kJ
ry s
st i
CH3COOH + NH4OH CH3COONH4 + H2O + 48.1 kJ
Assertion Reason
r ts ts
Q.32 Statement-1 :
e
The enthalpy of neutralization of the reaction between HCl and NaOH is
r
E xp pe
– 13.7 kCal / mol. If the enthalpy of neutralization of oxalic acid (H2C2O4) by a
x
ry E
strong base is – 25.4 kCal / mol, then the enthalpy change ( rH |) of the
y
i st tr
process H2C2O4 2H+ + C2O42– is 11.7 kCal / mol.
i s
em Statement-2 : H2C2O4 is a weak acid.
m
Ch Ch
e
(A) Statement-1 is true, statement-2 is true and statement-2 is correct explanation for statement-1.
(B) Statement-1 is true, statement-2 is true and statement-2 is NOT the correct explanation for statement-1.
(C) Statement-1 is true, statement-2 is false.
(D) Statement-1 is false, statement-2 is true.
r ts
Q.33 Statement-1: Standard enthalpy of isomerisation of an enantiomer into the other is zero.
xpe
Statement-2: The two enantiomers of any chiral compound have the same enthalpy of formation.
ts
E
(A) Statement-1 is true, statement-2 is true and statement-2 is correct explanation for statement-1.
y r
is tr pe
(B) Statement-1 is true, statement-2 is true and statement-2 is NOT the correct explanation for statement-1.
x
em
(C) Statement-1 is true, statement-2 is false.
ryE
C h(D) Statement-1 is false, statement-2 is true.
i s t
hem
C
Page # 10
ANSWER KEY THERMOCHEMISTRY
EXERCISE-1
r ts
tskJ/mol
–r800 p e
Q.1 – 1200 kJ/mol Q.2
p e Q.3
x
– 88 kJ/mol
E
E x –266 kJ/mol and –824 kJ/mol Q.6try–108.7 kJ / mol
Q.4 128 kJ
– 40 kJ/mol tr
y Q.8 –1560 kJ mol
Q.5
i s
Q.7
i s –1
hem
Q.9 (a) e
h m
3201 kJ/mol; (b) 3199.75 kJ/mol
C
Q.10C(a) 100.3 g; (b) 101.69 g Q.11 – 700 Kcal/mol
Q.12 65564 kJ /mol Q.13 22 kJ/mol
Q.14 Cis-2-butene Trans-2-butene
ts Hr = ?
r ts
er
p H of AgF(s) = 6 kJ/mol ; H AgCl = 95E
rH = – 3.3 kJ/mol
x x pe
Q.15 – 75 kJ/mol
ry E Q.16
tr y kJ/mol
i
Q.17 – 18.7 kCal i
mQ.20 72 kJ mol
h e m h e
Q.19 mole % O (g) = 37.14, H O(g) = 62.86
C Q.23 213 kJ / mol
–1
C
2 2
ryE Q.34 E
Q.33
s t
100 kJ / mol
i
(a) 885 kJ/mol (b) 890 kJ/mol
tryQ.35 2K
e m
Q.36 –30 kJ/mol Q.37 i sJ
C = 12.68 J/mole-K, w = 0, U = –31.7
m
Ch Exercise-2
Ch
e
Q.1 D Q.2 C Q.3 B Q.4 B
Q.5 B Q.6 D Q.7 C Q.8 B
Q.9 C
Q.14 rD
ts
Q.10 C Q.11 C Q.12 B
Q.13 B
x pe Q.15 C Q.16 B
ts
Q.17 A
yE Q.22 B
Q.18 C Q.19 D Q.20 B
r
Q.21 B
is tr Q.23 C
xQ.24 A pe
Q.25 B m
e ryE
Q.28 h
C
Q.26 B Q.27 A
i t
sQ.31 ABD
em
AD Q.29 ABCD Q.30 ABCD
Q.32 D Q.33 A
C h
Page # 11