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9 (a) In some chemical reactions, bonds are broken in the reactant molecules and new bonds are formed to make the product molecules - Edexcel - GCSE Chemistry - Question 9 - 2022 - Paper 1

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9 (a) In some chemical reactions, bonds are broken in the reactant molecules and new bonds are formed to make the product molecules. (i) Which row is correct about ... show full transcript

Worked Solution & Example Answer:9 (a) In some chemical reactions, bonds are broken in the reactant molecules and new bonds are formed to make the product molecules - Edexcel - GCSE Chemistry - Question 9 - 2022 - Paper 1

Step 1

i) Which row is correct about the energy changes for these processes?

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Answer

The correct answer is B. When breaking a bond, energy is released, and when making a bond, energy is absorbed. In reactions, breaking old bonds requires energy, while forming new bonds releases energy.

Step 2

ii) Hydrogen reacts with fluorine.

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Answer

To determine the total energy change, we first find the energy required to break the bonds in the reactants and then compare it with the energy released in forming the bonds in the products.

  1. Energy required to break bonds:

    • Breaking 1 H—H bond: 436 kJ
    • Breaking 1 F—F bond: 562 kJ

    Total energy required = 436 + 562 = 998 kJ

  2. Energy released to form bonds:

    • Forming 2 H—F bonds: 2 × 158 kJ = 316 kJ

  3. Overall energy change:

    Overall energy change = Energy required - Energy released

    Overall energy change = 998 - 316 = 682 kJ

Thus, the overall energy change for the reaction is +682 kJ.

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