Thermochemistry Heat of Precipitation Precipitation Question 1 3
-3
3
-3
100 cm of 1 mol dm barium chloride solution, BaCl2, is mixed with 100 cm of 1 mol dm sodium sulphate solution, Na2SO4, to form precipitate, barium sulphate. The mixture is stirred well before measuring the temperature. The thermochemical equation for the precipitation of barium sulphate is given as: 2+
2-
Ba (aq) + SO4 (aq)
BaSO4 (s) ; ∆H = -42kJ
Calculate (a) The quantity of heat given off in the reaction (b) The maximum temperature change of the mixture -1 o
[Specific heat capacity of reaction mixture,c: 4.2J g
-1
-3
C ; density of reaction mixture, 1.0g cm ]
Question 2 3
-3
3
-3
25 cm of 0.5 mol dm sodium chloride solution was mixed with 25 cm of 0.5 mol dm silver o o nitrate solution. The temperature of the reaction mixture rose from 28 C to 31.9 C. Determine the heat of precipitation of silver chloride, AgCl and construct the energy level diagram of the precipitation reaction. -1 o
[Specific heat capacity,c: 4.2J g
-1
-3
C ; density of solution, 1.0g cm ]
Question 3 3
-3
Calculate the highest temperature reached when 50 cm of 2 mol dm calcium chloride, CaCl2 3 -3 solution reacts with 50 cm of 2 mol dm sodium carbonate, Na2CO3 solution. The initial o temperature of both the solution is 29 C. The thermochemical equation for the precipitation of calcium carbonate is: 2+
2-
Ca (aq) + CO3 (aq)
CaCO3 (s) ; ∆H = +12kJ mol -1 o
[Specific heat capacity,c: 4.2J g
-1
-1
-3
C ; density of solution, 1.0g cm ]
Question 4 -3
The heat of precipitation of lead(II) sulphate, PbS O4 is -50kJ. When 1.0 mol dm sodium sulphate, Na2SO4 solution was mixed together with a solution of lead (II) nitrate, Pb(NO3)2, 3.0kJ of heat was released. Calculate the volume of sodium sulphate, Na2SO4 solution that was used.
Heat of Displacement Question 1 3
An excess zinc powder is added to 25 cm of copper (II) sulphate solution to determine the he at o of displacement of copper for the reaction. The temperature of the solution rises from 30 C to o 38 C. The thermochemical equation for the reaction of zinc and copper(II) sulphate solution is given as : Zn (s) + Cu
2+
(aq)
2+
Zn (aq) + Cu (s); ∆H = -217 kJ
Calculate (a) (b) (c) (d)
The temperature change of the solution The amount of heat given off in the reaction The number of moles of copper(II) sulphate reacted The concentration of copper(II) sulphate solution. -1 o
[Specific heat capacity of reaction mixture,c: 4.2J g
-1
-3
C ; density of reaction mixture, 1.0g cm ]
Question 2 3
-3
An excess of zinc powder is added to 50 cm of 0.12 mol dm iron (II) sulphate solution. The o temperature of iron (II) sulphate solution increased by 2.2 C. Calculate (a) The number of moles of iron formed (b) The heat of displacement of iron from iron ( II) sulphate solution -1 o
[Specific heat capacity of reaction mixture,c: 4.2J g
-1
-3
C ; density of reaction mixture, 1.0g cm ]
Question 3 3
-3
Excess zinc, Zn powder is added to 50 cm of 0.2 mol dm copper (II) sulphate, CuSO4 solution. o The temperature of the reaction mixture rises b y 10 C. Determine the heat of displacement of copper, Cu from its salt solution by zinc, Zn and construct the energy level diagram of the displacement reaction -1 o
[Specific heat capacity,c: 4.2J g
-1
-3
C ; density of solution, 1.0g cm ]
Question 4 3
-3
When excess zinc, Zn powder is added to 50 cm of 2.0 mol dm of hydrochloric acid,HCl, the o o temperature of the solution changes from 27 C to 57 C. Calculate the heat of displacement for the reaction. 2HCl (aq) + Zn (s)
ZnCl2 (aq) + H2 (g) -1 o
[Specific heat capacity,c: 4.2J g
-1
-3
C ; density of solution, 1.0g cm ]
Question 5 3
Calculate the iron, Fe produced when excess aluminium, Al powder is added to 200cm of iron o (II) sulphate, FeSO4 solution. The temperature of the reaction mix ture rises by 6.4 C. The thermochemical equation for the displacement of iron, Fe from its salt solution by aluminium, Al is 2+
3Fe
3+
-1
3Fe (s) + 2Al (aq); ∆H = -268.8 kJ mol
(aq) + 2Al (s) -1 o
[Specific heat capacity,c: 4.2J g iron = 56]
-1
-3
C ; density of solution, 1.0g cm ; relative atomic mass of
Question 6 3
-3
Calculate the changes of temperature when excess zinc, Zn is added to 50cm of 0.1 mol dm iron (II) sulphate, FeSO4 solution. The thermochemical equation for the d isplacement of iron, Fe by magnesium, Mg is: Mg (s) + Fe
2+
2+
(aq)
Mg -1 o
[Specific heat capacity,c: 4.2J g
-1
-1
(aq) + Fe (s); ∆H = -200 kJ mol -3
C ; density of solution, 1.0g cm ]
Heat of Neutralisation Question 1 3
-3
3
Neutralisation reaction occurs when 50 cm of 0.5 mol dm sulphuric acid reacts with 25 cm of -3 o 2 mol dm sodium hydroxide solution. The temperature rises by 8 C in the reaction mixture. The chemical equation is given as: H2SO4 (aq) + 2 NaOH (aq)
Na2SO4 (aq) + 2 H2O (l)
(a) Calculate the number of moles of water produced (b) Calculate the heat changes in the reaction (c) If the reaction is repeated using hydrochloric acid of the same concentration, determine the temperature rise of the reaction mixture. -1 o
[Specific heat capacity of reaction mixture,c: 4.2J g
-1
-3
C ; density of reaction mixture, 1.0g cm ]
Question 2 3
-3
3
-3
When 50 cm of 2 mol dm potassium hydroxide solution is added to 100 cm of 2 mol dm nitric acid, neutralization occurs. The thermochemical equation for the reaction is shown as: KNO3 (aq) + H2O (l); ∆H = -57 kJ
HNO3 (aq) + KOH (aq)
(a) Calculate the number of moles of water formed (b) What is the temperature rise of the reaction mixture? -1 o
[Specific heat capacity of reaction mixture,c: 4.2J g
-1
-3
C ; density of reaction mixture, 1.0g cm ]
Question 3 3
-3
3
-3
When 100 cm of 1.2 mol dm of hydrochloric acid, HCl is added to 100 cm of 1.2 mol dm of o o ammonia solution, the temperature of the reaction mixture change from 27 C to 34.5 C. Calculate the heat of neutralization of hydrochloric acid and ammonia solution. -1 o
[Specific heat capacity,c: 4.2J g
-1
-3
C ; density of solution, 1.0g cm ]
Question 4 3
-3
200 cm of 1 mol dm sodium hydroxide, NaOH solution was added to a fixed volume of 0.5 -3 mol dm dilute sulphuric acid, H2SO4. Calculate the quantity of heat given off and the volume of dilute sulphuric acid, H2SO4. -1 o
[Specific heat capacity,c: 4.2J g
-1
-3
-1
C ; density of solution, 1.0g cm ; ∆H = -57.3 kJ mol ]
Heat of Combustion Question 1 3
0.3 g ethanol is burnt completely and the heat given off is used to heat up 150 cm of water. What is the temperature rise of water if heat of co mbustion of ethanol, C2H5OH is – 1376 kJ -1 mol ? -1 o
[Specific heat capacity of water,c: 4.2J g H,1;C,12;O,16]
-1
-3
C ; density of water, 1.0g cm ; relative atomic mass:
Question 2
The thermochemical equation of the combustion of butan-1-ol is as shown below: 4 CO2 (g) + 5H2O (l) ; ∆H = -2600 kJ
C4H9OH (l) + 6 O2 (g)
3
o
o
Calculate the mass of butan-1-ol that will heat up 500cm of water from 28 C to 50 C in a complete combustion. -1 o
[Specific heat capacity of water,c: 4.2J g H,1;C,12;O,16]
-1
-3
C ; density of water, 1.0g cm ; relative atomic mass:
Question 3
The heat given off when 1.5g propanol (C3H7OH) was burned in excess oxygen raises o temperature of 1500 g of water by 9.2 C. Calculate the heat of combustion of propanol -1 o
[Specific heat capacity,c: 4.2J g H,1;C,12;O,16]
-1
-3
C ; density of solution, 1.0g cm ; relative atomic mass:
Question 4 o
In an experiment, the temperature of bomb calorimeter is raised by 4.5 C when 2.20 g of sucrose, C12H22O11 is burnt in it. Given that 15.5J of energy is required to raise the temperature of the o calorimeter and its content by 1 C, Determine the heat of combustion of sucrose. [ Relative atomic mass: H,1;C,12;O,16]
Question 5 3
How much charcoal is required to boil 2.5 dm of water? -1 o
-1
-3
[Specific heat capacity of water,c: 4.2J g C ; density of water, 1.0g cm ;room temperature of o -1 water, 27 C; fuel value of charcoal, 35kJ g ]
