Correct Answer - Option 4 :
(ii) and (iv)
Concept:
Enthalpy of reaction:
- The heat of reaction is also known as the Enthalpy of reaction. It is the amount to be added or removed during a chemical reaction to keep all of the substances present at the same temperature.
- It is used in calculating the amount of energy per mole either released or produced in a reaction.
- The process is exothermic if ΔH is negative and the process is endothermic if ΔH is positive.
- The heat of formation is the amount of heat absorbed or evolved when one mole of a compound is formed from its constituent elements.
Explanation:
-
Neutralization reaction occurs when a solution of an acid is mixed with a solution of a base in a test tube.
- The result of the reaction is the production of salt and water with the evolution of heat.
NaOH (strong base) + HCl (strong acid) → NaCl (salt) + H2O
CH3COOH + KOH → CH3COOK +H2O
- When a strong base and a weak acid reacts, the resultant is a solution with pH greater than 7, that is, basic.
- When a strong acid reacts with a weak base, the resultant solution has a pH lesser than 7, and the solution is acidic.
- When both are strong, the resultant solution is neutral.
- Whatever may be the case, the ultimate combination is the combination of a proton and a hydroxyl ion to give water. The combination takes place as follows:
H+ + OH- → H2O
- The combination releases heat and this heat is known as the heat of neutralization.
- When a strong acid and a strong base react, generally the heat of neutralization is constant about -57kJ/mol.
- When one of the components is weak, the enthalpy of neutralization decreases.
- As the reaction releases heat or is exothermic in nature, the temperature increases and the test tube becomes hot.
- Hence, when a solution of an acid is mixed with a solution of a base in a test tube, the temperature of the solution increases and salt formation takes place.
Hence, the correct option is both (ii) and (iv).
