Which reaction is endothermic?
A.
\(\mathrm{CaCO}_{3} \rightarrow \mathrm{CaO}+\mathrm{CO}_{2}\)
B.
\(\mathrm{CaO}+2 \mathrm{HCl} \rightarrow \mathrm{CaCl}_{2}+\mathrm{H}_{2} \mathrm{O}\)
C.
\(2 \mathrm{Ca}+\mathrm{O}_{2} \rightarrow 2 \mathrm{CaO}\)
D.
\(\mathrm{Ca}+2 \mathrm{HCl} \rightarrow \mathrm{CaCl}_{2}+\mathrm{H}_{2}\)
Exam No：0620_w18_qp_11 Year：2018 Question No：34
Answer:
A
Knowledge points:
5.1.1. State that an exothermic reaction transfers thermal energy to the surroundings leading to an increase in the temperature of the surroundings
5.1.2. State that an endothermic reaction takes in thermal energy from the surroundings leading to a decrease in the temperature of the surroundings
5.1.3. Interpret reaction pathway diagrams showing exothermic and endothermic reactions
5.1.4. State that the transfer of thermal energy during a reaction is called the enthalpy change
5.1.5. Define activation energy
5.1.6.1. reactants
5.1.6.2. products
5.1.6.3. enthalpy change of the reaction
5.1.6.4. activation energy
5.1.7. State that bond breaking is an endothermic process and bond making is an exothermic process and explain the enthalpy change of a reaction in terms of bond breaking and bond making
5.1.8. Calculate the enthalpy change of a reaction using bond energies
Solution:
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