Which of the following is a displacement reaction? MCQ with Answer and Explanation

Explanation:
Neutralization is the reaction of an acid with a base to produce salt and water. However, the resulting solution is not always neutral (pH 7) because the salt may undergo hydrolysis. If the acid is strong and base weak (e.g., HCl + NH₄OH), the salt (NH₄Cl) is acidic, pH < 7. If acid is weak and base strong (CH₃COOH + NaOH), salt is basic, pH > 7. Only strong acid-strong base gives pH 7.

Explanation:
DAP, (NH₄)₂HPO₄, supplies nitrogen (18% N) and phosphorus (46% P₂O₅). It is a widely used phosphorus-rich fertilizer. Potassium is not present. NPK complex fertilizers provide all three. DAP is highly water-soluble, making phosphorus readily available. In soil, DAP temporarily increases pH around granules due to ammonia, but later nitrification lowers pH. Application: usually at sowing time.

Explanation:
Potassium (K) is at the top of the reactivity series, meaning it is the most reactive among the given metals. The order of reactivity (decreasing): K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu > Ag > Au. Potassium reacts violently with water and oxygen. Copper (Cu) is relatively unreactive and is found native in nature. Exam trick: Remember 'Please Stop Calling Me A Cute Zebra...' mnemonic.