224
Thermochemistry
amp for 8 mm 53 sec raises the temperature of the mixture from 24 605°C
to 26 328°C
(b) The specific heat of a liquid First, 300 g of it are put in the calorimeter in
place of the water, then a current of 0 742 amp is passed for 3 mm 22 sec,
raising its temperature from 21 647°C to 22 406°C
(c) The enthalpy change per mole of precipitated PbI 2 when 25 0 ml of 6 00 vi
Nal are added with stirring to 300 ml of 0 250 M Pb(NO 3 ) 2 contained in the
calorimeter A current of 0 900 amp passing for 8 mm 18 sec through the
heater immersed in the reaction mixture causes a temperature rise only
0 750 of the rise observed for the reaction Also write the equation for the
reaction involved
(d) The enthalpy change per mole of KBrO 3 when 15 0 g of solid KBrO 3 are
dissolved in 200 ml of water in the calorimeter This is the so called heat
of solution ' After the salt is dissolved, a current of 0 800 amp passing for
10 mm 38 sec is required in order to regain the initial temperature of the
water Also write the equation for this reaction
(e) The enthalpy of fusion per mole of p-iodotoluene, C 7 H 7 I When 21 8 g of
p-iodotoluene are added to 200 ml of water in the calorimeter, the crystals
(being immiscible with water and also more dense) sink to the bottom As
current is passed through the heater, the temperature of the mixture rises
until the p-iodotoluene starts to melt, at this point, all of the electrical
energy is used for fusion and none for raising the temperature A current
of 0 820 amp passing for 4 mm 41 sec is required for the period in which
the temperature stays constant and before the temperature again begins to
rise, as both the water and the liquidp-iodotoluene rise above the melting
point of 34 0°C Write the equation for the reaction '
10 A metal X, whose specific heat is 0 119 cal/g °C, forms an oxide whose composition is 32 00% O
(a) What is the empirical formula of the oxide
9
(b) What is the exact atomic weight of the metal
0
11 A metal Y, whose specific heat is 0 0504 cal/g °C, forms two chlorides, whose
compositions are 46 71% Cl and 59 42% Cl
(a) Find the formulas of the chlorides
(b) What is the exact atomic weight of the metal
9
12 (i) Use Table 14-1 to determine the standard enthalpy of reaction, in kcal,
for each of the following reactions
(«) Give the values of the standard enthalpies of reaction in kjoules
(in) Calculate the change in standard internal energy (A£°) for each of the
reactions
(a) FeO (s) + H 2(9) <=*Fe (s) + H 2 O (()
(b) 4NH 3(9 > + 50 2(s) ft 6H 2 0 (9) + 4NO (9)
(c) Zn (sl + 2HC1« W > ?± H 2(9) + ZnCl 2(M ,
(d) 2FeO (g) + J0 2(fl) ?± Fe 2 0 3(s)
(e) 3N0 2(91 + H 2 0 m ft 2HN0 3(M) + NO (S)
(f) 2N 2 0 (9) ft 2N 2(9) + 0 2(9)
13 Calculate the standard enthalpy change (per mole) for the following reactions
Also write the equation for the reaction in each case
Thermochemistry
amp for 8 mm 53 sec raises the temperature of the mixture from 24 605°C
to 26 328°C
(b) The specific heat of a liquid First, 300 g of it are put in the calorimeter in
place of the water, then a current of 0 742 amp is passed for 3 mm 22 sec,
raising its temperature from 21 647°C to 22 406°C
(c) The enthalpy change per mole of precipitated PbI 2 when 25 0 ml of 6 00 vi
Nal are added with stirring to 300 ml of 0 250 M Pb(NO 3 ) 2 contained in the
calorimeter A current of 0 900 amp passing for 8 mm 18 sec through the
heater immersed in the reaction mixture causes a temperature rise only
0 750 of the rise observed for the reaction Also write the equation for the
reaction involved
(d) The enthalpy change per mole of KBrO 3 when 15 0 g of solid KBrO 3 are
dissolved in 200 ml of water in the calorimeter This is the so called heat
of solution ' After the salt is dissolved, a current of 0 800 amp passing for
10 mm 38 sec is required in order to regain the initial temperature of the
water Also write the equation for this reaction
(e) The enthalpy of fusion per mole of p-iodotoluene, C 7 H 7 I When 21 8 g of
p-iodotoluene are added to 200 ml of water in the calorimeter, the crystals
(being immiscible with water and also more dense) sink to the bottom As
current is passed through the heater, the temperature of the mixture rises
until the p-iodotoluene starts to melt, at this point, all of the electrical
energy is used for fusion and none for raising the temperature A current
of 0 820 amp passing for 4 mm 41 sec is required for the period in which
the temperature stays constant and before the temperature again begins to
rise, as both the water and the liquidp-iodotoluene rise above the melting
point of 34 0°C Write the equation for the reaction '
10 A metal X, whose specific heat is 0 119 cal/g °C, forms an oxide whose composition is 32 00% O
(a) What is the empirical formula of the oxide
9
(b) What is the exact atomic weight of the metal
0
11 A metal Y, whose specific heat is 0 0504 cal/g °C, forms two chlorides, whose
compositions are 46 71% Cl and 59 42% Cl
(a) Find the formulas of the chlorides
(b) What is the exact atomic weight of the metal
9
12 (i) Use Table 14-1 to determine the standard enthalpy of reaction, in kcal,
for each of the following reactions
(«) Give the values of the standard enthalpies of reaction in kjoules
(in) Calculate the change in standard internal energy (A£°) for each of the
reactions
(a) FeO (s) + H 2(9) <=*Fe (s) + H 2 O (()
(b) 4NH 3(9 > + 50 2(s) ft 6H 2 0 (9) + 4NO (9)
(c) Zn (sl + 2HC1« W > ?± H 2(9) + ZnCl 2(M ,
(d) 2FeO (g) + J0 2(fl) ?± Fe 2 0 3(s)
(e) 3N0 2(91 + H 2 0 m ft 2HN0 3(M) + NO (S)
(f) 2N 2 0 (9) ft 2N 2(9) + 0 2(9)
13 Calculate the standard enthalpy change (per mole) for the following reactions
Also write the equation for the reaction in each case