Name: _________________________________________
Date:____________________________
Homework 6:
1.) A 50.0 mL sample of very dilute HCl and 50.0 mL of very dilute NaOH are at 19.50oC to begin with.
After mixing the two in a styrofoam cup, the temperature rises to 21.21oC. Calculate the heat of the
reaction. (HINT: the density of the HCl, NaOH, and the mixed solutions can be assumed to be that
of water 1.00 g/mL)
C = 4.184 J/goC
qrxn = - qH2O
50.0 mL of water from HCl + 50.0 mL of water
from NaOH
= essentially 100.0 mL of water!
100.0 mL x 1.00 grams/mL = 100. grams of water
qwater = mwaterCwaterTwater
qwater = 100. grams (4.184 J/goC)(21.21oC – 19.50oC)
qwater = 100. grams (4.184 J/goC)(1.71oC)
qwater = 715 J
Since the qwater is equal but opposite in sign of the qrxn
since the qwater = 715 J then the qrxn = - 715 J
2.) Using the electron configuration for Zn, draw all the orbital box diagrams. Write the complete set of
quantum numbers for electrons 1, 5, 9, 21, and 26
1
5
1s
9
2s
2p
3s
21
3p
n, l, ml, ms
1st: 1, 0, 0, + ½
5th: 2, 1, -1, + ½
9th: 2, 1, 0, - ½
21st: 3, 2, -2, + ½
26th: 3, 2, -2, - ½
4s
26
3d
3.) Define Electronegativity: the propensity of an atom to draw the electron density towards itself in a
compound.
4.) Define Electron Affinity: when an atom is able to completely take away an electron from another
species and become a negatively charged ion (textbook definition: the energy change associated
with one mole of electrons being added to one mole of gaseous atoms or ions)
5.) Which species is the most X atom on the periodic table? Which species is the least? – Given that –
what is the trend for X values?
F
____ ______ most X
____Fr
and Cs_______
least X
Circle the correct answer:
X values
increase
X values
increase
decrease
going down a column
decrease
going from left to right across a row (main group!)
6.) Given the following compounds, classify them based on their bonding as containing ionic, polar
covalent, or non-polar covalent bonds:
a. GaAs : gallium is a metal and arsenic is a non-metal, therefore predict IONIC
b. NH3 (NH bonds only): both are non-metals, not same non-metal and not CH, therefore
POLAR COVALENT
c. BaO: metal + non-metal therefore IONIC
d. SO2 (SO bonds only): non-metal (S) + non-metal (O) not same non-metals and not CH
therefore POLAR COVALENT
e. ZnO: metal + non-metal therefore IONIC
f.
NaH: metal + non-metal therefore IONIC
g. O2: non-metal + non-metal and same bonded to itself therefore NON-POLAR
COVALENT
7.) Work on your Lewis structures handout!! Pages 1-9!