classification of substance 1) list the properties of a substance that would def
ID: 822252 • Letter: C
Question
classification of substance
1) list the properties of a substance that would definitely establish that the material is ionic.
2) if we classify substances as ionic , molecular , macromolecular , or metallie , in if any categories are all the members .
a. insoluble in water ?
b. electrical conductors in the melt ?
c. soluble in all commmon solvents ?
d. solids at room temperature ?
3) a given substance is a white solid at 25 C . it melts at 80 C without decomposing , and the melt has a small electrical conductivity . what would be the classification of substance based on this information ?
4) a white solid melts at 1000 C . the melt does not conduct electricity . classify the substance as best you can from these properties .
Explanation / Answer
((((1) )))))properties of ionic substance-
a)Ionic compounds have high melting points and high boiling points.
b) Ionic compounds have higher enthalpies of fusion and vaporization than molecular compounds
c) Ionic compounds are hard and brittle
d)Ionic compounds conduct electricity when they are dissolved in water.
When ionic compounds are dissolved in water the dissociated ions are free to conduct electric charge through the solution. Molten ionic compounds (molten salts) also conduct electricity.
e) Ionic solids are good insulators.
Although they conduct in molten form or in aqueous solution, ionic solids do not conduct electricity very well because the ions are bound so tightly to each other.
((((((2))))))))))) if we classify compound as--
1) ionic, then
a. insoluble in water - ----------->>>>no
b. electrical conductors in the melt ----->>>>yes
c. soluble in all commmon solvents ------------------>>>>>>> (yes)all are soluble only in water, and insoluble in organic solvent.
d. solids at room temperature ------->>>>>(No) some are are liquid known as ionic liquid..
2) molecular, then
a. insoluble in water - No (some of them are soluble in water like sugar, some are insoluble in water like polymeric material)
b. electrical conductors in the melt ------>>>>>>>>>>>no
c. soluble in all commmon solvents --------->>>>no (depends on nature of polarity in covalent compound)
d. solids at room temperature ------>>>>no (many compound exist in liquid(methanol, ethanol, hexane etc) as well as gas at the room temperature(O2, H2, CO2 etc), solid like graphite, dimomd etc)
3)macromolecular
A macromolecule is a very large molecule commonly created by polymerization of smaller subunits.
properties---
does not characterize smaller molecules is their relative insolubility in water and similar solvents. Many require salts or particular ions to dissolve in water. Similarly, many proteins will denature if the solute concentration of their solution is too high or too low.
Some examples of macromolecules are synthetic polymers (plastic, synthetic fibre, and synthetic rubbber), graphene, and carbon nanotube.
Natural molecules are for example the bio-polymers such as DNA, carbohydrade, proteins and lipids, or polyphenol.
a. insoluble in water ---------->>>yes (since very large molecule comprise of very large covalent bond)
b. electrical conductors in the melt ---->>>no
c. soluble in all commmon solvents ----------------->>>>>>>>> no (depends on nature of polarity in compounds)
d. solids at room temperature ------>>no (not all are solid at room temperatue like most of the lipid, but some exist in solid material at room temperature like polymeric material plastics,synthetic fibre, and synthetic rubbber)
4) metallic
properties---
In a metallic lattice the attractive forces/bonds between metal ions and the surrounding mobile sea of electrons are strong. Strong attractive forces/bonds require a high temperature to be overcome/broken. E.g. The MP for chromium is 1900oC, and for iridium, 2450oC.(* Some metals have low melting points such as mercury, -39oC, and the Group 1 metals: Li = 180oC, Na = 98oC, rubidium = 39oC,caesium = 29oC.)
The attractions, between the polar solvent molecules and the metallic lattice cations/electrons, are not strong enough to pull them from the lattice. (Also: electrons are too tiny to be successfully surrounded by solvent molecules.)
Non-polar molecules have no permanently charged parts that can be attracted to the charged cations/electrons.The mobile sea of electrons can move within the metallic lattice to be an electric current.
Even when the metallic lattice has been broken by high temperatures, so that the metal is in the liquid state, there is still a mobile sea of electrons which can move to be an electric current. (E.g. Liquid mercury conducts.)
The mobile sea of electrons can move around metal cations in the lattice as the cations are moved. This allows the metal to change shape without breaking.
a. insoluble in water ------------>>>>>>>>>>>>yes
b. electrical conductors in the melt----->>>>>yes (conduct electricity even in solid state at room temperature)
c. soluble in all commmon solvents ------>>>>no (not soluble in any solvent )
d. solids at room temperature ---->>>>>yes
((((((((3))))))))))
substace must be covalent(molecular), since it has low melting point, and conduct electricity very little in liquid state.
{Covalent substances in the molten/liquid state are very very poor conductors and are often considered not to be conductors}
((((((4)))))))))))
compound must be covalent(some covalent compound usually have high melting point), since all compound like metallic, ionic will conduct electricity in melt but only compound which does not conduct electicity in melt is covalent compound.
note::::----- Metallic substances conduct in all states (except gas). This is because a metal has delocalised electrons, which means they are not bound to one single atom, rather they can move from one atom to another. This is why a metallic compound is conductive. An ionic compound is not conductive in the solid but is in the liquid/molten state. This is because in the molten state there are free moving ions, which allow electrons to flow through the compound.
bsed on above information it is clear that compound cann't be metallic or ionic, and only possibiliy left behind is molecular or covalent compound.
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