Chapter 14, Problem 14.2YT

(a)

Interpretation Introduction

Interpretation:

If used by the hazmat crew to extinguish fire and what would happen if they simply used water, following reason should be explain.

Concept introduction:

The hazmat team was well aware of the five classes of fires and the types of fire extinguishers required.

• • Class A: The ordinary combustible materials such as wood, paper, plastics. Use water only.
• • Class B: Flammable liquids such as organic solvents, gasoline, petroleum oil, paint, as well as flammable gases such as methane, propane, butane.  Use: carbon dioxide or dry-chemical extinguishers.
• • Class C: Electrical fires: use the same extinguishers as Class B fires.
• • Class D: The combustible metals such as $Na,K,Mg$: use dry-powder extinguishers (graphite or sodium chloride powders pressurized with nitrogen gas).
• • Class K: Cooking oils and greases: use wet-chemical extinguishers (e.g., aqueous potassium carbonate, containing detergents to improve the wettability of the nonpolar grease).

(b)

Interpretation Introduction

Interpretation:

It would not be wise to use sodium metal and benzophenone to purify chlorinated solvents such as dichloromethane, the reason behind this has to be speculated.

Concept introduction:

Solvent importance of organic synthesis:

Solvents are used for many chemical reactions, in which traces of water or oxygen would in contamination and unsuccessful synthesis.

The organic solvent is heated to boiling its vapour rise up the glassware and is condensed back to its liquid state using a water filled condenser. The repeated process of heating a solvent to boiling and condensing its vapour is known as reflux.

The moisture/air-free solvent is collected in the receiver flask, which may be removed for use via syringe. A nitrogen bubbler system is used to flush the solvent still with an inert gas to prevent moisture and oxygen from dissolving in the solvent, and prevent a build-up of pressure that would result in a dangerous explosion.