Choose the right description ()
A. The positions in ionic crystals are occupied by molecules.
B. The carbonyl double bond is polar bond.
C. The oxidation number of an atom of any free element is zero.
D. Nitrogen gas is used in lighter than air balloons.
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Viscosity increases with the increase of () ①:Intermolecular attraction ②:Temperature ③:Height ④:Density of liquid
A. ①④
B. ②③
C. ①③
D. ②④
Choose the wrong characterization of surface tension ()
A. Unbalanced forces
B. Resists being broken
C. Tends to be drawn outward
D. At the very surface
Choose the ionic crystals ()
A. diamond
B. NaCl
C. Ice
D. SiC
Choose the right name of 丙醛 and 环己酮 ()
A. Propanone and Cyclohexanal
B. Propanol and Cyclohexene
C. Propanal and Cyclohexanone
D. Propane and Cyclohexane
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