In this set of practice questions, we will go over the main types of questions on calorimetry including the heat capacity, the heat of reaction, finding the final temperature of a mixture, constant pressure calorimetry, and constant-volume calorimetry.
A few important concepts and formulas you will need to solve these questions.
Heat capacity and specific heat are correlated by the following formula:
When solving a problem related to heat capacity and heat transfer, remember that most of the time, it is assumed the heat is not lost, and it only flows from the object with a higher temperature to the colder one:
The heat transfer to/from the calorimeter is determined by its temperature change and the heat capacity:
qcal = Ccal x ΔT
The heat capacity of the calorimeter is determined experimentally and is already known when measuring the heat/enthalpy of a reaction.
Remember, the enthalpy change (ΔH) is equal to the heat when the pressure is constant:
On the other hand, a bomb calorimeter is an equipment that measures ΔE for combustion reactions. This can be seen in the equation of internal energy change:
ΔE = q + w
w = PΔV and ΔV is zero when the volume is constant. So, for a constant volume, ΔE = q, and therefore, the bomb calorimeter measures the energy change of a chemical reaction.
The experiment is carried out in an insulated sealed vessel called a bomb which is designed to withstand high pressures. The bomb is placed in a water container and by measuring its temperature change caused by the reaction, we determine the heat of the calorimeter.
The links to the corresponding topics are given below:
1.
How much heat in kJ is required to warm 1.50 L of water from 25.0 oC to 100.0 °C? (Assume a density of 1.0 g/mL for the water.)
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2.
What is the final temperature when a 40 g sample of water at 90 °C is mixed with a 60 g sample at 25 °C?
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3.
How much heat does it take to increase the temperature of a 540.6-g sample of Fe from 20.0 °C to 84.3 °C? The specific heat of iron = 0.450 J/g °C.
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4.
Calculate the specific heat capacity of a metal if a 17.0 g sample requires 481 J to change the temperature of the metal from 25.0 °C to 67.0 °C?
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5.
Calculate the energy of combustion for one mole of butane if burning a 0.367 g sample of butane (C4H10) has increased the temperature of a bomb calorimeter by 7.73 °C. The heat capacity of the bomb calorimeter is 2.36 kJ/ °C.
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6.
How many joules of energy is required to melt 40.0 g of ice at 0 °C? The heat of fusion (ΔHfus) for ice is 334.0 J/g.
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7.
How many kJ of energy does it take to change 36.0 g of ice at -15.0 °C to water at 0. °C ? The specific heat of ice is 2.10 J/g°C and the heat of fusion (ΔHfus) for ice is 334.0 J/g. Ignore the significant figures for this problem.
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8.
The enthalpy change for the reaction is given below:
2CH3OH(l) + 3O2(g) → 4H2O(l) + 2CO2(g) ΔH = -1452.8 kJ
a) What quantity of heat is released for each mole of water formed?
b) What quantity of heat is released for each mole of oxygen reacted?
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9.
How much heat will be released if 44.8 g of SO2 is reacted with an excess of oxygen according to the following chemical equation?
2SO2(g) + O2(g) → 2SO3(g), ΔH° = –198 kJ
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10.
What is ΔH° for the following reaction
2C6H6(l) + 15O2(g) → 12CO2(g) + 6H2O(l), ΔH° = ? kJ
if the consumption of 27.3 g of benzene (C6H6) produces 1144 kJ of heat?
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11.
Based on the heat of reaction for the chlorination of methane, how much heat will be released if 233.6 grams of hydrochloric acid are formed?
CH4(g) + 3Cl2(g) → CHCl3(l) + 3HCl(g), ΔH° = -334 kJ
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12.
Calculate how many kJ of heat-energy will be released when 12.65 g of magnesium carbonate reacts with 650. mL of 0.400 M hydrochloric acid?
MgCO3(s) + 2HCl(aq) → MgCl2(aq) + H2O(l) + CO2(g), ΔH° = –112 kJ
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This was so helpful,thank you so much!
Glad to hear that, Chirambo.