A buffer solution is prepared by adding NaH2PO4 to a solution of H3PO4 (phosphoric acid). H3PO4(aq) = H+(aq)+H2PO4-(aq)
What happens if NaOH is added?

Kerosene is lighter than water and so it floats on the water and continues to burn. Carbon (IV) oxide blankets the flame cutting off the supply of oxygen and extinguishing the fire.

Explanation:

As water is heavier than kerosene, it slips down permitting the kerosene to rise to the surface and continue to burn. Besides, the existing temperature is so high that the water poured on the fire would evaporate before it can extinguish the fire. Thus the kerosene fire cannot be extinguished with water.