heat of hydration

Examples of heat of hydration in the following topics:

• Solutions and Heats of Hydration

  • When ions dissolve in water, the stabilizing interactions that result release energy called the "heat of hydration."
  • M^+ (g) + X^-(g) \to M^+ (aq) + X^-(aq)$ [heat of hydration]
  • The heat (enthalpy) of solution (Hsolution) is the sum of the lattice and hydration energies ( Hsolution = Hhydration + Hlattice energy).
  • A hot solution results when the heat of hydration is much greater than the lattice energy of the solute.
  • Predict whether a given ionic solid will dissolve in water given the lattice energy and heat of hydration

• Elimination Reactions of Alcohols

  • This is yet another example of how leaving group stability often influences the rate of a reaction.
  • Four examples of this useful technique are shown below.
  • It should be noted that the acid-catalyzed dehydrations discussed here are the reverse of the acid-catalyzed hydration reactions of alkenes.
  • The dehydration reaction is shown by the blue arrows; the hydration reaction by magenta arrows.
  • The predominance of the non-Zaitsev product (less substituted double bond) is presumed due to steric hindrance of the methylene group hydrogens, which interferes with the approach of base at that site.

• Naming Hydrates

  • The name of a hydrate follows a set pattern: the name of the ionic compound followed by a numerical prefix and the suffix -hydrate.
  • The name of a hydrate follows a set pattern: the name of the ionic compound followed by a numerical prefix and the suffix "-hydrate."
  • The notation of hydrous compound · nH2O, where n is the number of water molecules per formula unit of the salt, is commonly used to show that a salt is hydrated.
  • An anhydride can normally lose water only with significant heating.
  • Generate the chemical formula and systematic name of a given inorganic hydrate

• Specific Heat

  • However, it would be pretty inconvenient to measure the heat capacity of every unit of matter.
  • The specific heat is the amount of heat necessary to change the temperature of 1.00 kg of mass by 1.00ºC.
  • Note that the total heat capacity C is simply the product of the specific heat capacity c and the mass of the substance m, i.e.,
  • The specific heat of water is five times that of glass and ten times that of iron, which means that it takes five times as much heat to raise the temperature of water the same amount as for glass and ten times as much heat to raise the temperature of water as for iron.
  • Listed are the specific heats of various substances.

• Water’s High Heat Capacity

  • The high heat capacity of water has many uses.
  • The heat is quickly transferred to a pool of water to cool the reactor.
  • Water has the highest specific heat capacity of any liquid.
  • Specific heat is defined as the amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius.
  • In fact, the specific heat capacity of water is about five times more than that of sand.

• Specific Heat and Heat Capacity

  • Heat capacity is a measure of the amount of heat energy required to change the temperature of a pure substance by a given amount.
  • the molar heat capacity, which is the heat capacity per mole of a pure substance.
  • How much heat is required to raise the temperature of 36 grams of water from 300 to 310 K?
  • Specific heat capacity is the measure of the heat energy required to raise the temperature of a given quantity of a substance by one kelvin.
  • Latent heat of melting describes tœhe amount of heat required to melt a solid.

• Physical and Chemical Changes to Matter

  • Many physical changes are reversible (such as heating and cooling), whereas chemical changes are often irreversible or only reversible with an additional chemical change.
  • Blending a smoothie, for example, involves two physical changes: the change in shape of each fruit and the mixing together of many different pieces of fruit.
  • The formation of gas bubbles is often the result of a chemical change (except in the case of boiling, which is a physical change).
  • When exposed to water, iron becomes a mixture of several hydrated iron oxides and hydroxides.
  • The heat from cooking an egg changes the interactions and shapes of the proteins in the egg white, thereby changing its molecular structure and converting the egg white from translucent to opaque.

• The Heat-Shock Response

  • Heat shock response is a cell's response to intense heat, including up-regulation of heat shock proteins.
  • In biochemistry, heat shock is the "effect of subjecting a cell to a higher temperature than that of the ideal body temperature of the organism from which the cell line was derived. "
  • Heat shock response is the cellular response to heat shock includes the transcriptional up-regulation of genes encoding heat shock proteins (HSPs) as part of the cell's internal repair mechanism .
  • Additionally, heat shock proteins are believed to play a role in the presentation of pieces of proteins (or peptides) on the cell surface to help the immune system recognize diseased cells.
  • The up-regulation of HSPs during heat shock is generally controlled by a single transcription factor; in eukaryotes this regulation is performed by heat shock factor (HSF), while σ32 is the heat shock sigma factor in Escherichia coli.

• Heat Pumps and Refrigerators

  • The basic components of a heat pump in are a condenser, an expansion valve, an evaporator and a compressor .
  • The quality of a heat pump is judged by how much heat transfer Qh occurs into the warm space compared with how much work input W is required.
  • We define a heat pump's coefficient of performance (COPhp) to be
  • Since the efficiency of a heat engine is Eff=W/Qh, we see that COPhp=1/Eff.
  • Explain how the the components of a heat pump cause heat to transfer from a cold reservoir to a hot reservoir

• Water’s Solvent Properties

  • This is referred to as a sphere of hydration, or a hydration shell, and serves to keep the particles separated or dispersed in the water.
  • Dissociation occurs when atoms or groups of atoms break off from molecules and form ions.
  • Consider table salt (NaCl, or sodium chloride): when NaCl crystals are added to water, the molecules of NaCl dissociate into Na+ and Cl– ions, and spheres of hydration form around the ions.
  • The positively-charged sodium ion is surrounded by the partially-negative charge of the water molecule's oxygen; the negatively-charged chloride ion is surrounded by the partially-positive charge of the hydrogen in the water molecule.
  • When table salt (NaCl) is mixed in water, spheres of hydration form around the ions.