ET III Ch.12 Hydrates and Hydrolysis

What is a hydrate?

Compound in which there is a chemical union between water and the molecules of certain substances

What do hydrates look like?

Crystalline in appearance

What is the water held in the union in a hydrate?

The water of crystallization

Give an example of a formula of a hydrate

CuSO4 · 5 H2O

How can the water of crystallization be removed?

By heating the compound

• This can be classified as a decomposition reaction

Give an example of the water of crystallization being removed

CuSO4 · 5 H2O → CuSO4 + 5 H2O

Anhydrous copper sulfate can return to its crystallized form when _______ is re-added

Water

The water of crystallization is the fixed number of water molecules present in one formula unit of a _____

Salt

Some _________ can have two different waters of crystallization giving them two distinctive forms

hydrates

What is plaster of Paris?

Calcium Sulfate in its partly anhydrous form

Give the chemical equation for plater of Paris turning into gypsum

(CaSO4)2 · H20 + 3 H2O → 2 CaSO4 · 2 H2O

What happens when water is added to partly anhydrous calcium sulfate?

It becomes gypsum

• This is a synthesis reaction

What has plaster of Paris traditionally been used for?

It has been employed in embalming to close the back of the skull after a cranial autopsy

How is plaster of Paris used to close the back of the skull after a cranial autopsy?

It hardens into gypsum and provides a seal for the cut edges of bone over which the scalp is sutured

What has recently replaced the method of using plaster of Paris to close the back of the skull after a cranial autopsy?

calvaria clamps have been used instead

When is plaster of Paris an excellent tool in embalming?

In cases of extreme cranial trauma to reassemble broken bones

What is another use of plaster of Paris

Can be used as a hardening agent in solid autopsy compounds

How does plaster of Paris work as a hardening agent in solid autopsy compounds?

Acts as a dehydrating agent and effectively removes water from the viscera

• It is from this that we get the modern term “hardening compound” when describing solid autopsy compounds

What can special hydrates do?

Certain hydrates can attract additional water while others spontaneously release water of crystallization to surrounding air

What is a hydrophilic substance?

Substances that have an affinity for water and attract additional water

What’s another word for hydrophilic?

Hygroscopic

What is the process called that allows some hydrates to absorb enough moisture from the air under ordinary atmospheric conditions to dissolve?

Deliquescence

What’s an example of a deliquescence substance?

Calcium Chloride

What is calcium chloride commonly used for?

• Applied to rural roads during dry summer months to control dust production

• Also serves as a deicer since it attracts water and lowers the freezing point

What are deliquescent substances commonly used in?

In caskets as mold inhibitors

How does mold get into caskets and onto bodies?

• Mold spores in the surrounding air find their way inside open caskets

• When the casket is closed, the spores along with moist air grow rampant in the dark

What are hydrates that give up their water of crystallization to the surrounding air?

Efflorescent

Give an example of an efflorescent substance

Sodium carbonate appears as a dry powder because it readily loses its water of crystallization to the air under ordinary atmospheric conditions

How should deliquescent and efflorescent substances be stored?

They must be kept in tightly sealed containers in order to maintain their hydrated forms

What is hydrolysis?

Process by which water is split by other compounds

• Constituents of water are then introduced into the products of the reaction

Hydrolysis is a chemical principle of what substance?

Salts

Give an example of a hydrolysis equations

CuSO4 + 2 HOH → Cu(OH)2 + H2SO4

• This is a double replacement reaction

What is the criteria of identifying a hydrolysis reaction?

• Water appears on the reactant side of the equation

  • Water is written as “HOH” rather than H2O in order to emphasize the reacting constituents of water are H+ and OH-

• The products of a hydrolysis reaction are an acid and a base

What is the result of a reaction between a strong acid and a strong base?

A neutral solution

Give an example of the equation of a reaction between a strong acid and a strong base

strong acid + strong base → salt + water

In hydrolysis, the acid and base strength that are formed must be of different ____________

Strength

Give some examples of the acid and bases formed in hydrolysis

• salt + water → strong acid + weak base

• salt + water → weak acid + strong base

What is the single most important factor in the initiation of decomposition?

Hydrolysis

How does hydrolysis take place in human remains?

Proteins, carbohydrates, and fats are split into amino acids, monosaccharides, fatty acids, and glycerin by the action of water and enzymes

• Water chemically reacts with these substances rather than merely physically dissolving them