The type of energy changes that accompany the mixing of a strong acid to a strong base is

Analyze the question: When a strong acid is mixed with a strong base, what form of energy change is observed?

Concept: This is a neutralization reaction. A strong acid (e.g. HCl) and a strong base (e.g. NaOH) react completely to form salt and water:

HCl + NaOH → NaCl + H₂O

The essential step is the combination of H⁺ and OH⁻ ions to form water:

H⁺(aq) + OH⁻(aq) → H₂O(l) ΔH ≈ −57.3 kJ/mol

Forming the new bonds in water releases energy, so the reaction is exothermic. The energy is given out as heat, and the temperature of the mixture rises. This quantity is called the heat (enthalpy) of neutralization.

Checking the options:

• A. Electrical: no electricity is produced, since this isn't a cell setup.
• B. Heat: the temperature rises, so this is correct.
• C. Light: no light is given off, unlike combustion or some other reactions.
• D. Sound: there is no noticeable sound.

Tip: Remember "neutralization = exothermic." If a WASSCE or JAMB question asks about energy change in acid-base neutralization, the answer is almost always heat. For strong acid and strong base, the value is about −57 kJ/mol. For weak acids or bases, it is slightly less because some energy is used to ionize them.