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Lesson Worksheet: Energy Changes in Reactions Chemistry • 10th Grade

In this worksheet, we will practice identifying types of energy and relating changes in energy to chemical bonding and chemical reactions.

Q1:

The change in energy during a chemical reaction may be explained in terms of electrostatic interactions between subatomic particles. Which of the following best describes the change in energy when a covalent bond is formed?

  • ABond formation absorbs energy due to increased electrostatic attraction between protons and electrons.
  • BBond formation releases energy due to increased electrostatic attraction between protons.
  • CBond formation releases energy due to increased electrostatic attraction between protons and electrons.
  • DBond formation releases energy due to increased electrostatic repulsion between protons.
  • EBond formation absorbs energy due to increased electrostatic repulsion between protons and electrons.

Q2:

The decomposition of calcium nitrate proceeds according to the following equation: 2Ca(NO)()kJ2CaO()+4NO()+O()3222ssgg+369

How much energy is needed to decompose 3.2 moles of calcium nitrate? Give your answer as a whole number.

Q3:

The chemical equation for the decomposition of magnesium carbonate is as follows: MgCO()kJMgO()+CO()32ssg+117

Based on this chemical equation, which of the following statements is true?

  • A117 kJ of energy is released when a single molecule of MgCO3 decomposes.
  • B117 kJ of energy is needed to make 1 mole of MgCO3 decompose.
  • C117 kJ of energy is needed to make 42 g of MgCO3 decompose.
  • D117 kJ of energy is needed to make a single molecule of MgCO3 decompose.
  • E117 kJ of energy is released when 1 mole of MgCO3 decomposes.

Q4:

What name and symbol are given to the overall change in energy at constant pressure during a chemical reaction?

  • APotential difference, Δ𝑉
  • BTemperature change, Δ𝑇
  • CEnthalpy change, Δ𝐻
  • DEntropy change, Δ𝑆
  • EActivation energy, 𝐸

Q5:

Which of these statements does not describe the conservation of energy in a chemical reaction?

  • AEnergy is neither created nor destroyed during a chemical reaction.
  • BThe energy contained in the bonds of reactant molecules always equals the energy contained in the bonds of product molecules.
  • CIf the energy of a system increases, then the energy of the surroundings decreases by the exact same amount.
  • DEnergy can only be transferred from one form to another.
  • EIf the energy of a system decreases, then the energy of the surroundings increases by the exact same amount.

Q6:

Why do chemical reactions usually involve a change in energy?

  • AThe process of making or breaking bonds during a chemical reaction absorbs and releases energy.
  • BThe process of splitting the nucleus of an atom releases large amounts of energy.
  • CIn chemical reactions, atoms are destroyed and converted into energy.
  • DThe nuclei move faster during chemical reactions and so require more energy.

Q7:

Which of the following is not a type of energy that a chemical reaction may produce?

  • ALight
  • BElectric
  • CColor
  • DHeat
  • EChemical

Q8:

The reaction of calcium oxide with water produces calcium hydroxide and releases 57.3 kJ of energy. How much energy is released when 10 g of calcium oxide is reacted with excess water? Give your answer to 1 decimal place.

Q9:

The value of Δ𝐻 when liquid water freezes to solid water is 6.01 kJ/mol. What is the value of Δ𝐻 when solid water melts to liquid water?

Q10:

Fuels can also be used to provide energy. Which of the following fuels does not produce energy through a chemical reaction?

  • ABiofuels
  • BFuel cells
  • CNuclear fuel
  • DFossil fuel
  • EBatteries

This lesson includes 28 additional questions for subscribers.

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