Ch 5 -
% Comp., Empirical Formula
% Comp., Empirical Formula
What is the % composition of H in CH4?
4 g H/mol CH4
16 g CH4/mol
= 25% H
Draw a valid Lewis structure for BF3.
(should have B in center, 6 total e- around B, 3 F's with 3 sets of lone pairs on each F)
The hybridization of CO2
sp
Is C2H2 polar or nonpolar?
Non-Polar
Balance the following equation:
___ N2 + ___ F2 --> ___ NF3
___ N2 + __3_ F2 --> __2__ NF3
What is the empirical formula of C6H12O6?
CH2O
How many valence electrons in NO3-?
N = 5; O = 3 x 6 ; minus charge = 1
Total = 24
Molecules with sp3 hybridization have ______ electron domain geometry
tetrahedral
Which ONE is capable of H-bonding as a pure liquid?
A) C2H6; B) HI; C) CH3NH2; D) CH3COCH3
C) CH3NH2
N2 + 3H2 → 2NH3, how many moles of hydrogen are needed to fully react with 2.5 mol nitrogen?
7.5 mol H2
The empirical formula for succinic acid (MW = 118.1 g/mol) is C2H3O2. What is the molecular formula?
The weight of C2H3O2 is 59.1 g/mol.
(118.1 g/mol)/(59.1 g/mol)=2
C2H3O2 (x 2 for all in formula) => C4H6O4
Which diatomic molecule contains the strongest bond?
N2, O2, F2, H2
N2 = must be triple bond in Lewis structure.
Triple bonds are shorter and stronger than doubles or singles.
Which would have the largest bond angle? OF2, CH4, NH3?
CH4
Why is CO2 nonpolar but SO2 polar?
CO2 linear - dipoles cancel
SO2 bent - dipoles don't cancel
In the combustion reaction, what is the coefficient in front of O2?
__C2H6 + __ O2 --> ___ CO2 + __ H2O
_2_C2H6 + _7_ O2 --> _4__ CO2 + _6_ H2O
What is the empirical formula of a compound with 42.8%C and 57.1%O by mass?
42.8gC * 1 mol/12.011g = 3.56 mol C
57.1gO * 1mol/15.999g = 3.56 mol O
CO is the empirical formula
What is the formal charge on the middle N?
.. ..
:N=N=O:
+1
Valence - electrons in box = 5 - 4 = +1
What is the molecular geometry of CO32-?
trigonal planar
Rank in order of boiling point from lowest to highest:
CH3Cl, C2H6, CH3OH
C2H6, CH3Cl, CH3OH
Balance the following equation
CO2 + H2O --> C6H12O6 + O2
6 CO2 + 6 H2O --> C6H12O6 + 6 O2
A compound contains only N and H atoms, with 82.2% N, 17.8% H by mass. What is the empirical formula?
82.244 g N x (1 mol N)/(14.01 g)=5.87 mol N
17.756 g H x (1 mol H)/(1.01 g)=17.58 mol H
(mole H)/(mole N)= (17.58 mol)/(5.87 mol)=3
Empirical formula = NH3
Draw two valid resonance structures of CO2.
.. ..
:O=C=O:
.. _ ..
:O=C-O:
..
The molecular geometry of ClF3
T-shape
The molecule with the highest boiling point out of the following: CH4, AgCl, CH3CH2OH.
AgCl (ion-ion is strongest IMF!)
How many g of LiNO3 are needed to react with excess PbSO4 to produce 250 g of Li2SO4?
(LiNO3 = 68.95 g/mol; Li2SO4 = 109.94 g/mol)
2LiNO3 + PbSO4 --> Li2SO4 + Pb(NO3)2
313.5g LiNO3