Inorganic Chemistry Chapter 12: Carbon
Characteristics of SiC (silicon carbide).
"Carborundum" Extremely durable; used as an abrasive. 2 forms known; analogous to diamond and lonsdaleite (no graphite form due to size mismatch of unpaired p orbitals). Alternating Si and C atoms; each connected to 4 of other type. Moissonite: gemstone quality hexagonal SiC.
What are the two types of salt-like carbides?
(1) Dicarbides - contains C2^2- ion. (2) Methides - contains C^4- ion.
(1) Dicarbides are ____ with nitrogen; atoms are connected by a ____. (2) Describe the C-C bonds in dicarbides.
(1) isoelectronic triple bond (2) The C-C bonds are not formed by reaction but exist in lattice.
What is the formula for graphite fluoride?
(CF)n
Average bond order of graphite?
1.33 [= 4 bonds (2 single, 1 double) / 3 atoms]
What are the two ways graphite can stack?
AB (most common) ABC
How is HCN produced in lab?
Acidification of cyanides. CN- + H3O+ --> HCN + H2O
How is HCN used industrially?
Alkali metal cyanides are produced by rxn between HCN and the corresponding metal hydroxide or carbonate. HCN + NaOH --> H2O + NaCN 2HCN + Na2CO3 --> H2O + CO2 + 2NaCN
What do all fullerenes have in common?
All have 12 5-membered rings and varying amounts of 6-membered rings. Have curvature due to the 5-membered rings. The carbon atoms are sp2 hybridized; each bonded to 3 others.
What are the two possible configurations of carbon nanotubes?
Armchair Zig Zag
How is the cyanamide ion produced industrially?
By the direct reaction of calcium carbide and nitrogen gas at room temperature. CaC2 + N2 --> CaNCN + C
Where are the C atoms in interstitial carbides?
C atoms occupy interstices between atoms in metal lattice.
What is the most common dicarbide and what forms when it reacts with water?
CaC2 Forms acetylene gas. CaC2 + 2H2O --> C2H2 + Ca(OH)2
Describe the structure of graphite.
Carbon is sp2 hybridized; trigonal planar geometry. Carbon atoms are joined to form flat, 6-membered rings.
The CN- ion forms strong complexes with ___, ___, and ___ and is used in the ___ of these metals.
Cu+ Ag+ Au+ extraction
What are the three types of carbon-nitrogen compounds?
Cyanides Cyanogen Cyanamide ion
How does cyanogen react with fire?
Cyanogen is flammable and burns with very hot, violet flames to produce CO2 and N(g). C2N2 + 2O2 --> 2CO2 + N2
What are the allotropes of carbon?
Diamond, lonsdaleite, graphite
Describe the structure of diamond.
Each carbon is connected to 4 others; sp3 hybridized; tetrahedral geometry. It is a network covalent solid; has covalent bonds that extend in 3 dimensions through structure.
Describe the structure of lonsdaleite.
Each carbon is connected to 4 others; sp3 hybridized; tetrahedral. Has hexagonal symmetry.
Characteristics of graphite.
Electrically conductive. Less dense than diamond (2.22 g/cm3)
Characteristics of fullerene C60.
First to be discovered; most common fullerene. Spherical 12 5-membered rings and 20 6-membered rings.. Each 5-membered ring is surrounded exclusively by 6-membered rings.
What forms when methide reacts with H2O?
Forms methane gas. Al4C3 + 12H2O --> 3CH4 + 4Al(OH)3
How is graphite fluoride formed?
Graphite fluoride is formed when graphite reacts with fluorine at high temperatures.
Characteristics of HCN?
HCN is a gas at room temperature. Has extensive hydrogen bonding. Is a weak acid (Ka = 7.2*10^-10); CN- ion is a base. CN- + H2O --> HCN + OH-
Why does graphite feel slippery?
Layers can slide over one another.
Characteristics of cyanogen.
Linear molecule with formula C2N2. Atoms are connected in the order of N-C-C-N; can be viewed as 2 CN- molecules joined by a C-C bond. Melting point: -27.9 C Boiling point: 21.2 C (gas @ room temp.)
What are the three types of carbides?
Salt-like Covalent Interstitial
Characteristics of fullerene C70.
Second most common fullerene. Elongated shape. (Has 10 more atoms than C60 --> more 6-mem. rings --> elongated shape) 12 5-membered rings and 25 6-membered rings.
What two elements form covalent carbides and why?
Silicon and boron. They are similar in size and electronegativity to carbon.
Uses of cyanamide ion.
Used as fertilizer and reacts with water to produce ammonia and calcium carbonate. CaNCN + 3H2O --> CaCO3 + 2 NH3
Characteristics of interstitial carbides.
Very hard materials; have very high melting points. Electrical conductivity of the metal is unchanged.
Physical properties of diamond.
Very hard. Very high melting point. Density = 3.5 g/cm3
How rare is lonsdaleite?
Very rare; was originally found in meteorites.
Carbon nanotube characteristics.
Visualized as rolled sheet of graphite. Carbon atoms are sp2 hybridized. Only 6-membered rings.
Complete fluorination of graphite gives a solid of what color?
White
Characteristics of the cyanamide ion.
[NCN]2- Linear molecule; isoelectronic with CO2.
The conductivity of carbon nanotubes varies depending on the ____ and ____ of the tube.
diameter configuration
Carbon nanotubes may be ____ or ____.
multi-walled single-walled
Graphite fluoride is often ___.
nonstoichiometric
Covalent carbides are at least ___.
partially covalent.
In graphite fluoride, a change in hybridization of Carbon atoms from sp2 to sp3 results in ___ and ___.
the rings switching from flat to puckered a loss of electrical conductivity
