Heats of Reaction

Multiple Choice Quiz

[Note: the terms “heat“ and “enthalpy“ are interchangeable in some of these questions]

Try this as often as you like.
You will get a different set of questions each time you attempt this quiz.

TRUE or FALSE?
An exothermic reaction is one where heat is released
1. TRUE
2. FALSE
How can you determine if a reaction is endothermic?
1. The temperature of the system decreases.
2. The temperature of the system increases.
3. The temperature of the system remains constant.
A few grams of calcium were placed in a test tube containing dilute hydrochloric acid. The temperature of the mixture rose as a reaction was seen to take place.
Which two of the following statements are correct?
1. Bonds were broken and new bonds were made.
2. This was an exothermic reaction.
3. Heat was absorbed by the system.
4. Heat was released by the system because this was an endothermic reaction.
Of the following statements, only three are correct about the burning of a hydrocarbon in oxygen.
Select these three statements.
1. Heat is released.
2. Carbon dioxide is formed.
3. Water vapour is produced.
4. The reaction is endothermic.
What is the principal component of natural gas?
1. Methane (CH₄)
2. Ethane (C₂H₆)
3. Propane (C₃H₈)
4. Ethyne (C₂H₂)
What are the two main constituents of bottled gas, which is used to fuel patio heaters?
1. Propane (C₃H₈)
2. Butane (C₄H₁₀)
3. Pentane (C₅H₁₂)
4. Ethene (C₂H₆)
The heat in kilojoules that is released or absorbed in a chemical reaction when the number of moles indicated in the balanced equation react completely, is known as
1. the heat of reaction
2. the heat of solution
3. the heat of combustion
4. kilogram calorific value
Study the energy profile diagram shown and select the correct type of reaction for this diagram.
1. Exothermic
2. Endothermic
3. Neither exothermic nor endothermic
In an experiment, 500 ml of 0.1 M hydrochloric acid (HCl) is added to 400 ml of sodium hydroxide (NaOH) solution.
The acid and base neutralise each other according to the equation:
HCl + NaOH → NaCl + H₂O
How many moles of acid and base were there originally?
1. 0.05 mole of HCl and 0.05 mole of NaOH
2. 0.05 mole of HCl and 0.04 mole of NaOH
3. 0.5 mole of HCl and 0.5 mole of NaOH
4. 0.5 mole of HCl and 0.4 mole of NaOH
In a chemical reaction, 100 cm³ of 0.2 M H₂SO₄ is neutralised by 200 cm³ of NaOH solution.
H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O
How many moles of acid and base were used?
1. 0.02 mole of H₂SO₄ and 0.04 mole of NaOH
2. 0.02 mole of H₂SO₄ and 0.02 mole of NaOH
3. 0.2 mole of H₂SO₄ and 0.4 mole of NaOH
4. 0.2 mole of H₂SO₄ and 0.2 mole of NaOH
When a strong acid and a strong base neutralise each other, there is an increase in the temperature of the mixture. The heat released is given by the equation:

ΔH = m × c × ΔT, ΔT = temperature change
What do m and c represent in this equation?
1. m = mass of acid + base, c = specific heat capacity of acid/base mixture
2. m = mass of acid + base, c = heat capacity of acid/base mixture
3. m = mass of acid, c = specific heat capacity of acid/base mixture
4. m = mass of base, c = heat capacity of acid/base mixture
In an experiment, a student neutralises 0.1 mole of HCl with 0.1 mole of NaOH with the release of 5.72 kJ of heat energy.
Use the information given to find the heat of reaction for:
HCl + NaOH → NaCl + H₂O
1. -57.2 kJ/mol
2. -5.72 kJ/mol
3. -28.6 kJ/mol
4. +2.86 kJ/mol
In an experiment, 50 ml of HCl were neutralised by 100 ml of NaOH. The heat capacity of the mixture was 400 J/K and the temperature of the mixture rose by 7 K.
How much energy was released during this reaction?
1. 2,800 KJ
2. 57.1 KJ
3. 420,000 kJ
4. 140,000 kJ
In an experiment to find the heat of reaction for:
HCl + NaOH → NaCl + H₂O
The apparatus shown was used, where HCl was reacted with NaOH.
Select three precautions that would lead to a more accurate result.
1. Record the highest temperature reached
2. Repeat the experiment and get an average temperature rise.
3. Place a cover on the container.
4. Use a glass beaker.
5. Do not stir the mixture.
6. Measure the temperature in Kelvin rather than degrees Celsius.
Which two of the following statements about bond energy are correct?
1. Bond making releases energy and ΔH = negative
2. Bond breaking absorbs energy and ΔH = positive
3. Bond making releases energy and ΔH = positive
4. Bond breaking releases energy and ΔH = negative
The heat change that occurs in a reaction depends only on the initial and final states of the reaction, and is independent of the path followed.
This is also known as:
1. Hess's Law
2. Law of Conservation of Energy
3. Heat of Reaction
4. Kilogram Caloric Value
In a chemical reaction, 65 kJ of energy are needed to break all of the bonds of the reactants, and 85 kJ of energy are required to form the bonds of the products.
What is the heat of reaction?
1. 20 kJ
2. +20 kJ
3. −150 kJ
4. +150 kJ
It requires 425 kJ/mol to break the first C-H bond in the methane (CH₄) molecule, and 335 kJ/mol to break the fourth C-H bond.
In performing calculations involving bond energies, what value for the C-H bond energy is used?
1. An average value of different C-H bond energies obtained from different compounds containing the C-H bond.
2. An average value of C-H bond energies in methane.
3. The energy needed to break the first C-H bond in methane.
4. The energy needed to break the fourth C-H bond in methane.
The heat released when one mole of a substance is burned in excess oxygen is known as:
1. the heat of combustion.
2. the heat of formation.
3. the heat of neutralisation.
4. the heat of solution.
Considering the following reaction, what is the heat of combustion of sulfur?
2S_(s) + 3O_2(g) → 2SO_3(g), ΔH = -790 kJ/mol
1. -395 kJ/mol
2. +395 kJ/mol
3. +790 kJ/mol
4. -790 kJ/mol
In industry, the heat of combustion of a substance may be measured using a
1. bomb calorimeter
2. Hofmann voltameter
3. Liebig condenser
4. conical flask
The diagram shows an apparatus used for measuring the heat of combustion of a fuel.
What are the parts labelled X and Y?
1. X = stirrer, Y = heating coil
2. X = stirrer, Y = calorimeter
3. X = thermometer, Y = heating coil
4. X = thermometer, Y = crucible
When using a bomb calorimeter, which one of the following is not necessary in order to get an accurate result?
1. The fuel sample must have a mass of 1.0 g exactly.
2. The water must be continuously stirred.
3. There must be excess oxygen.
4. The apparatus must be insulated.
The heat produced by a kilogram of fuel is known as its
1. kilogram calorific value
2. heat of reaction
3. heat of combustion
4. octane number
Propane (C₃H₈) has a relative molecular mass of 44, and its heat of combustion is -2222 kJ/mol.
What is its kilogram calorific value?
1. 50,500 kJ/kg
2. 25,250 kJ/kg
3. 0.0102 kJ/mol
4. 19.8 kj/mol
When one mole of methane is burned in excess oxygen, 890 kJ of heat energy is released.
Which one of the following equations best describes this reaction?
1. CH₄ + 2O_2(g) → CO_2(g) + 2H₂O, ΔH = -890 kJ/mol
2. CH₄ + 2O_2(g) → CO_2(g) + H₂O, ΔH = +890 kJ/mol
3. CH₄ + O_2(g) → CO_2(g) + 2H₂O, ΔH = -890 kJ/mol
4. 2CH₄ + 4O_2(g) → 2CO_2(g) + 4H₂O, ΔH = +890 kJ/mol
The heat change that takes place when one mole of a substance is formed from its elements in their ground state is known as:
1. the heat of formation
2. the heat of neutralisation
3. the heat of combustion
4. the heat of reaction
In calculating the heat of formation, the substance must be formed from its elements in their standard state.
Which one of the following is not in its standard state?
1. O
2. H₂
3. Cl₂
4. S
5. N₂
The law which states that "Energy cannot be created nor destroyed, but may be converted from one form to another" is known as
1. Law of conservation of energy
2. Hess's Law
3. Joule's Law
4. Boyle's Law
"The heat change of a reaction depends only on the initial and final states of the reaction and is independent of the route taken" is known as
1. Hess's Law
2. Avogadro's Law
3. Boyle's Law
4. Joule's Law
The equation describing the heat of formation of ethane gas is
Which one of the following equations does not satisfy the conditions for the heat of formation?
Assume that the heats of formation values are correct.
The heat (enthalpy) changes for two reactions are shown below:
     S + O₂ → SO₂, ΔH = − 300 kJ
     2S + 3O₂ → 2SO₃, ΔH = − 800 kJ
What is the (heat) enthalpy change for the reaction below in kJ?
   2SO₂ + O₂ → 2SO₃
1. −200
2. −500
3. −1100
4. −1400
Which of the following processes is exothermic?
1. Br_(g) + e⁻ → Br⁻_(g)
2. Na_(s) → Na_(g)
3. Ca_(g) → Ca⁺_(g) + e⁻
4. I_2(g) → 2I_(g)
Which one of the following equations represents the standard heat (enthalpy) of formation of calcium fluoride?
1. Ca_(s) + F_2(g) → CaF_2(s)
2. Ca_(g) + F_2(g) → CaF_2(g)
3. Ca²⁺_(g) + 2F⁻_(g) → CaF_2(s)
4. Ca²⁺_(s) + 2F⁻_(g) → CaF_2(s)
25 cm³ of 1.0 mol dm⁻³ NaOH is added to 25 cm³ of 1.0 mol dm⁻³ HCl.
The temperature rise is 6^oC.
Which reactants will also give a temperature rise of 6^oC?
1. 50 cm³ of 1.0 mol dm⁻³ NaOH and 50 cm³ of 1.0 mol dm⁻³ HCl.
2. 25 cm³ of 2.0 mol dm⁻³ NaOH and 25 cm³ of 2.0 mol dm⁻³ HCl.
3. 50 cm³ of 0.5 mol dm⁻³ NaOH and 50 cm³ of 0.5 mol dm⁻³ HCl.
4. 100 cm³ of 0.25 mol dm⁻³ NaOH and 100 cm³ of 0.25 mol dm⁻³ HCl.
The table shows the heat of combustion of four straight chain alkanols.
What is the mass of water that could be heated from 20°C to 45°C by the complete combustion of 1.0 g of heptan-1-ol?
1. 0.38 kg
2. 0.032 kg
3. 0.044 kg
4. 0.36 kg
Which of the following is correct about the energy changes during bond breaking and bond formation?
1. Bond breaking is endothermic, bond formation is exothermic
2. Bond breaking is endothermic, bond formation is endothermic
3. Bond breaking is exothermic, bond formation is endothermic
4. Bond breaking is exothermic, bond formation is exothermic
Consider the following reactions:
S_(s) + 1½O_2(g) → SO_3(g) ΔH = −395 kJ mol⁻¹
SO_2(g) + ½O_2(g) → SO_3(g) ΔH = −98 kJ mol⁻¹
What is the ΔH value (in kJ mol⁻¹) for the following reaction:
S_(s) + ½O_2(g) → SO_2(g)
1. –297
2. +297
3. –493
4. +493
The ΔH values for the formation of two oxides of nitrogen are given below:
½N₂ + O₂ → NO₂, ΔH = −57 kJ mol⁻¹
N₂ + 2O₂ → N₂O₄, ΔH = +9 kJ mol⁻¹
Use these values to calculate ΔH (in kJ) for the following reaction:
2NO₂ + 2O₂ → N₂O₄
1. +123
2. -105
3. -48
4. +66
Which one of the following statements is correct about the reaction shown?
2SO_2(g) + O_2(g) → 2SO_3(g), ΔH = −196 kJ
1. 98 kJ of energy are released for every mole of SO_2(g) reacted.
2. 196 kJ of energy are released for every mole of SO_2(g) reacted.
3. 196 kJ of energy are absorbed for every mole of SO_2(g) reacted.
4. 98 kJ of energy are absorbed for every mole of SO_2(g) reacted.
Which statements are correct for all exothermic reactions?
1. The enthalpy of the products is less than the enthalpy of the reactants.
2. The sign of ΔH is always negative.
3. The reaction is rapid at room temperature.
1. 1 and 2 only
2. 1 and 3 only
3. 2 and 3 only
4. 1, 2 and 3
The equations and enthalpy changes for two reactions used in the manufacture of sulfuric acid are:
S_(s) + O_2(g) → SO_2(g) , ΔH = −300 kJ
2SO_2(g) + O_2(g) → 2SO_3(g), ΔH = -200 kJ
What is the enthalpy/heat change, in kJ ,for the reaction below?
2S_(s) + 3O_2(g) → 2SO_3(g)
1. −800
2. −400
3. −500
4. −100
The standard enthalpy change of formation values of two oxides of phosphorus are:
P₄ + 3O₂ → P₄O₆, ΔH = -1600 kJ mol^-1
P₄ + 5O₂ → P₄O₁₀, ΔH = -3000 kJ mol^-1
What is the enthalpy change, in kJ mol^-1, for the reaction below? P₄O₆ + 2O₂ → P₄O₁₀
1. -1400
2. +1400
3. +4600
4. -4600
Which type of reaction is referred to in the definition of standard enthalpy/heat change of formation?
1. The formation of a compound from its elements
2. The formation of a crystal from its ions
3. The formation of a molecule from its atoms
4. The formation of a compound from other compounds
What is the energy change (in kJ) when the temperature of 20 g of water increases by 10°C?
2. 20 × 10 × 4.18
3. 20 × 283× 4.18

Heats of Reaction

Multiple Choice Quiz[Note: the terms “heat“ and “enthalpy“ are interchangeable in some of these questions]

Multiple Choice Quiz

[Note: the terms “heat“ and “enthalpy“ are interchangeable in some of these questions]