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Chemistry LibreTexts

7.7.1: Practice Stoichiometry Part 3

  • Page ID
    236046
  • Exercise \(\PageIndex{1}\)

    2 NO (g) + O2 (g) \(\rightarrow\) 2 NO2 (g)  \(\Delta H \)=  – 114 kJ

    Is the reaction above endothermic or exothermic? What is the energy change when 0.633 moles of NO react?

    Answer

    Exothermic. Energy change is – 36.1 kJ, meaning that 36.1 kJ of energy is released.

    Exercise \(\PageIndex{1}\)

    CaCO3 (s) \(\rightarrow\) CO2 (g) + CaO (s) \(\Delta H \)=  + 192 kJ

    Is the reaction above endothermic or exothermic? What is the energy change when 2.87 grams of CaCO3 react?

    Answer

    Endothermic. Energy change is + 5.51 kJ, meaning that 5.51 kJ of energy is absorbed.

    Exercise \(\PageIndex{1}\)

    S8 (s) + 12 O2 (g) \(\rightarrow\) 8 SO3 (g)  \(\Delta H \)=  – 3166 kJ

    Is the reaction above endothermic or exothermic? What is the energy change when 26.7 grams of SO3 are produced?

    Answer

    Exothermic. Energy change is – 132 kJ, meaning that 132 kJ of energy is released.

    Exercise \(\PageIndex{1}\)

    2 HCl (g) \(\rightarrow\) H2 (g) + Cl2 (g) \(\Delta H \)=  + 185 kJ

    Is the reaction above endothermic or exothermic? What is the energy change when 489 grams of HCl react?

    Answer

    Endothermic. Energy change is + 1240 kJ, meaning that 1240 kJ of energy is absorbed.

     

     

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