Hydrochloric acid and sodium hydroxide react to produce water and sodium chloride in an endothermic reaction. Which statement must be true of the reaction?
A. More bond energy is absorbed on the reactants side than is released on the products side.
B. The total bond energy of water and sodium chloride is greater than the total bond energy of hydrochloric acid and sodium hydroxide.
C. The energy of each bond in water and sodium chloride is greater than the energy of each bond in hydrochloric acid and sodium hydroxide.
D. The bond energy used to break the bonds in hydrochloric acid and sodium hydroxide is less than the energy released to form the bonds in water and sodium chloride.
The answer is (B.) The total bond energy of water and sodium chloride is greater than the total bond energy of hydrochloric acid and sodium hydroxide
Let me point out that the question is flawed.
1. The reaction between HCl and NaOH is EXOTHERMIC by approximately 50 kJ/mol.
2. The use of bond energies to calculate delta H or to make conclusions based on delta H is valid ONLY for gases. These are not gases.
To determine which statement must be true of the reaction between hydrochloric acid and sodium hydroxide, we need to understand the concept of bond energy and how it relates to the reaction.
Bond energy refers to the amount of energy required to break a chemical bond in a molecule. It is also the energy released when a bond is formed. In endothermic reactions, the reactants have higher bond energy than the products. This means that more energy is absorbed by the reactants to break their bonds, while less energy is released when new bonds are formed in the products.
Now, let's examine each statement:
A. More bond energy is absorbed on the reactants side than is released on the products side.
This statement aligns with the concept of endothermic reactions. Therefore, this statement could be true.
B. The total bond energy of water and sodium chloride is greater than the total bond energy of hydrochloric acid and sodium hydroxide.
Based on the information given, we cannot determine the total bond energy of each compound. Therefore, this statement cannot be proven true or false.
C. The energy of each bond in water and sodium chloride is greater than the energy of each bond in hydrochloric acid and sodium hydroxide.
Again, we cannot directly compare the energy of each bond in these compounds based solely on the given information. Therefore, this statement cannot be proven true or false.
D. The bond energy used to break the bonds in hydrochloric acid and sodium hydroxide is less than the energy released to form the bonds in water and sodium chloride.
This statement aligns with the concept of endothermic reactions. Breaking the bonds in the reactants requires less energy than is released when the bonds in the products are formed. Therefore, this statement could be true.
Based on the understanding of endothermic reactions and bond energy, both statement A and statement D could be true. So, the correct answer is either A or D.