State the relationship between IMF and vapor pressure
A liquid with weak intermolecular forces evaporates more easily and has a high vapor pressure.
What is the bond order of NO3-?
3
1
1.5
1.3
State the electron domain, molecular shape, bond angle/s and polarity: CH2O
3, trigonal planar, 120, polar
Explain why CO is polar while CO2 is nonpolar.
O is more EN than C; CO has uneven distribution of e in bond, thus polar; CO2 is linear (symmetrical), charge distribution is even, thus non-polar
Explain why HCl is more soluble in water than Cl2.
HCl is a polar molecule (forms ion-dipole interaction with water) while Cl2 is non polar
What is ethyl acetate?
A solvent of medium polarity
If a molecule has 4 bonds and one lone pair, what is its shape?
see-saw
trigonal bipyramidal
T-shaped
square pyramidal
State the electron domain, molecular shape, bond angle/s and polarity: CH4
4, tetrahedral, 109.5, non-polar
Explain why pure carbon has a melting point of approximately 3550C while pure nitrogen has a melting point of -210C.
Carbon = giant covalent structure = strong bonding; N2 molecule = weak dispersion forces between particles = requires lesser energy to separate them
State the electron domain, molecular shape, bond angle/s and polarity: [NH4]+
4, tetrahedral, 109.5, non-polar
State the electron domain, molecular shape, bond angle/s and polarity: HCN
2, linear, 180, polar
State the electron domain, molecular shape, bond angle/s and polarity: BF3
3, trigonal planar, 120, non-polar
State the electron domain, molecular shape, bond angle/s and polarity: SO3
3, trigonal planar, 120, non-polar
Which would have the highest Rf?
non-polar molecule
very polar
intermediate polarity
slightly non-polar
Why is the melting point of HI higher than HBr?
HI has greater molar mass (more electrons) and so it has stronger dispersion forces than HBr
State the electron domain, molecular shape, bond angle/s and polarity: SO2
3, bent, 117.5, polar
Explain why polar molecules are often soluble in water while non-polar molecules are not. Include discussion on the intermolecular processes involved in dissolving.
soluble = IMF solute and IMF solvent are similar; water is polar = h-bonding and dipole dipole; nonpolar solute = dispersion (way weaker than IMF in solvent)
Give an example of a substance that is very soluble in water and has a pyramidal shape.
(answers may vary - NH3, PH3, ...)
In paper chromatography, why do we use pencil instead of pen in writing the starting line?
pencil = insoluble in solvent; pen = soluble; may interfere with the results
What element combines with another element by sharing 1 pair of valence e and combines with hydrogen to form a molecule that exhibits hydrogen bonding?
Fluorine
Explain why the melting point of HF does not follow the trend of the other hydrogen halides.
HF has hydrogen bonding as its main IMF; while HCl, HBr, HI have dipole-dipole which is a generally weaker IMF than Hydrogen bonding
Which of the following has the shortest bond
quadruple
single
triple
double
State the electron domain, molecular shape, bond angle/s and polarity: PH3
4, trigonal pyramidal, 107, polar
State the electron domain, molecular shape, bond angle/s and polarity: H2S
4, bent, 104.5, polar
State the electron domain, molecular shape, bond angle/s and polarity: [CO3]2-
3, trigonal planar, 120, non-polar
Give an example of a substance that has a very high 1st ionization energy, a very low BP and does not form bonds.
(answers may vary - any noble gas)
Explain the following trend in boiling points: CH4 < C2H6 < C3H8
All molecules are nonpolar = only dispersion forces = increase in mass = stronger dispersion forces = higher BP
State the electron domain, molecular shape, bond angle/s and polarity: BeI2
2, linear, 180, non-polar
What does "HPLC" stand for?
High Performance Liquid Chromatography
Give the two common materials used in TLC as the stationary phase
Alumina (Al2O3) and Silica (SiO2)
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