chemical reaction

Question

1. If you add a large amount of sodium monohydrogen phosphate to iron (III) chloride, you should observe no change when adding ammonium thiocyanate thereafter. Attempt to explain why the presence of sodium monohydrogen phosphate affects this process.

 

2. The equation below represents the general format of a combustion reaction, which by definition releases a large amount of energy in the form of heat. Knowing what you do about chemical reactions and the properties of gases, attempt to explain how a fire extinguisher is used to fight fires. 

C_xH_­y + O_2(g) -----> H₂O_(g) + CO_2(g)

Answer 1

1. The reaction of iron (III) chloride with excess sodium monohydrogen phosphate results in an insoluble compound that removes iron (III) from solution. As iron (III) would react with thiocyanate ion to give a soluble red compound, the absence of iron (III) due to precipitation by the monohydrogen phosphate prevents that the thiocyanate reaction.
2. Fire extinguishers contain a gas such as CO₂ , N₂, and in some cases a halogenated organic compound which do not support combustion and serve to dilute the oxygen in the atmosphere surrounding the fire; thereby, helping to extinguish the fire.