Solid phase
Official name
Acetylene II ice
Secondary names
C2H2 ice; Acetylene ice; C2H2-II
Type
Family
molecular solid
Class
non polar molecular solid
Compound type
organic molecular solid
Chemical composition
Formula
$C_2H_2$
Chemical formula
C2H2
Elemental formula
C2 H2
Isotope mixture type
terrestrial abundance
2.0
  Formula Name Family Number min-max Mole fraction Isotope mole fraction State Relevance
$C_2H_2$ Ethyne molecule 1 1.0 1 pure main
Chemical functions
  Function Number
$R\equiv CH$ 2
Chemical bonds
  Bond Number
$\equiv C-H$ 2
$-C\equiv C-$ 1
Class
molecular solids with apolar molecules (01)
Type
with polyatomic organic apolar molecules (CnHm...) (01.06)
Equivalent liquid
liquid acetylene
Phase name
C2H2-II
Phase type
crystalline
Crystal system
orthorhombic
Crystal class
dipyramidal
Crystal class symbol
mmm (D2h)
Crystal spacegroup
Cmca
Molar mass
26.037 $g/mol$
State NTP
gas
Phase transitions
Phase transition type Other phases Temperature - Pressure
solid-solid to C2H2-I ice above 133 K
solid-solid from metastable C2H2 ice above ~65 $\pm$5K
Phase transitions comments
irreversible transition from metastable phase. Stable below 133 K
Refringence type
biaxial
Refraction index $n_{\alpha}$
1.36
Pure color
colorless
Diaphaneity
transparent
Luster
vitreous
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