Problem Set 12 Solution
1.
2.
How many moles of oxygen are in 1,50 mol manganese(II) oxide?
Formula: Mn2+
O2MnO
The number of significant digits: 3
Given: 1.50 mol MnO
Target: ?mol O
Path: mol MnO 6 mol O
Relationship: 1 mol MnO = 1 mol O
the answer is 1.50 mol O
How many g of bromine are in 0.2 g potassium bromide?
Formula: K+
BrKBr
The number of significant digits: 1
We will use molar masses since we are converting g of a compound to g of atoms in the compound
Given: 0.2 g KBr Target: ?g Br
Path: g KBr6 mol KBr 6 mol Br 6 g Br
Relationship: 1 mol KBr = 1 mol Br
element
#moles
K
Molar mass
Product
1
39.10 g K
Br
1
79.90 g Br
Molar mass KBr
Computation:
3.
How many g of chlorine are in 0.25 g FeCl3? Name the compound.
Ions: Fe3+ Cl- it follows that iron has three positive charges and therefore, the name is iron(III) chloride
The number of significant digits: 2
We will use molar masses since we are converting g of a compound to g of atoms in the compound
Given: 0.25 g FeCl3
Target: ?g Cl
Path: g FeCl36 mol FeCl3 6 mol Cl 6 g Cl
Relationship: 1 mol FeCl3 = 3 mol Cl
element
#moles
Fe
Molar mass
Product
1
55.85 g Fe
Cl
3
106.4 g Cl
Molar mass FeCl3
Computation:
Note that the significant figures are correct.
4.
How many atoms of oxygen are in 0.1 mol [NO3]-? Name the compound.
Here we are only counting atoms of oxygen in this ion
The number of significant digit: 1
Given: 0.1 mol [NO3]Target: ?O atoms
Path: mol [NO3 ]- 6 mol O 6 O atoms
Relationship: 1 mol [NO3]- = 3 mol O
Computation:
5.
Note that the significant figures are correct.
Draw Lewis diagrams of these oxyanions: bromate ion (bromine is less electronegative than oxygen); sulfite ion; phosphite
ion; nitrate ion; carbonate ion. When drawing Lewis diagram of oxyanions follow the procedure that you have learned
in class.
a.
bromate ion [BrO3]- has one negative charge
n = 4 x 8 = 32
v = 7 + 3 x 6 + 1 = 26
s=6
b=3
lp = (32 - 2 x 6)/2 = 10
b.
sulfite ion [SO3]2- has two negative charges
n = 4 x 8 = 32
v = 6 + 3 x 6 + 2 = 26
s=6
b=3
lp = (32 - 2 x 6)/2 = 10
c.
phosphite [PO3]3- has three negative charges
n = 4 x 8 = 32
v = 5 + 3 x 6 + 3 = 26
s=6
b=3
lp = (32 - 2 x 6)/2 = 10
d.
nitrate ion [NO3 ]- has one negative charge
n = 4 x 8 = 32
v = 5 + 3 x 6 + 1 = 24
s=8
b=4
lp = (32 - 2 x 8)/2 = 8
Note that this is one of the possible arrangements of four bonds - it does not matter at this stage which one of them you draw.
e.
carbonate ion [CO3]2- has two negative charges
n = 4 x 8 = 32
v = 4 + 3 x 6 + 2 = 24
s=8
b=4
lp = (32 - 2 x 8)/2 = 8
Note that this is one of the possible arrangements of four bonds - it does not matter at this stage which one of them you draw.
6.
Write a symbol for each of the following elements, ions, isotopes or compounds that exist in nature:
a.
b.
c.
d.
e.
f.
g.
7.
beryllium-8
iodine
dicarbon hexachloride
calcium nitride
phosphide ion
cobalt(II) phosphide
dinitrogen trioxide
Write the name for each of the following elements, ions, isotopes or compounds that exist in nature:
a.
H2
hydrogen
b.
8.
I2
C2Cl6
Ca3N2
P3+
Co3P2
N2O3
nitrogen-15
-
c.
d.
e.
F
Cl2 O
MnS
f.
Cu3N
g.
CaI2
fluoride ion
dichlorine oxide
manganese(II) sulfide since sulfide ion S2- has two negative charges then the manganese
must also have two positive charges and therefore manganese(II)
copper(I) nitride since nitride ion N3- has three positive charges then the copper must only
one positive charge and therefore copper(I)
calcium iodide
Fill in the table - see an attempt at explanation in square brackets [formula begins with H implies acid]; formula ends with
[....OH] implies a base. Further, -ate ion implies an -ic acid; -ite implies an -ous acid and an absence of oxygen implies a
hydro..ic acid:
formula
acid or base
name the two ions
write formulas for ions
name the compound
H2 CO3
acid [H...]
hydrogen ion;
carbonate ion [! -ic
acid]
H+
(CO3)2-
carbonic acid
Be(OH)2
base [...OH]
beryllium ion; hydroxide
ion
Be2+
(OH)-
beryllium hydroxide
LiOH
base [....OH]
lithium ion; hydroxide
ion
Li+
(OH)-
lithium hydroxide
HClO2
acid [H....]
hydrogen ion; chlorite
ion [! -ous acid]
H+
(ClO2 )-
chlorous acid
H3 PO3
acid [H....]
hydrogen ion;
phosphite ion [! -ous
acid]
H+
(PO3 )3-
phophorous acid
Cu(OH)2
base [....OH]
copper(II) ion;
hydroxide ion
Cu2+
(OH)-
copper(II) hydroxide
Fe(OH)3
base [....OH]
iron(III) ion; hydroxide
ion
Fe3+
(OH)-
iron(III) hydroxide
HI
acid [H....]
hydrogen ion; fluoride
ion [no oxygen !
hydro...ic acid]
H+
H2 SO4
acid [H....]
hydrogen ion; sulfate
ion [! -ic acid]
H+
F-
(SO4)2-
hydroiodic acid
sulfuric acid
9.
Fill in the table:
name of the compound
acid or base
name the two ions
write formula of the two
ions
write the formula of the
compound
hydrosulfuric acid
acid
hydrogen ion; sulfide
ion
H+
S2-
H2 S
iodous acid
acid
hydrogen ion; iodite ion
H+
(IO2)-
HIO2
potassium hydroxide
base [...hydroxide in the
name]
potassium ion;
hydroxide ion
K+
(OH)-
KOH
cobalt(III) hydroxide
base [...hydroxide in the
name]
cobalt(III) ion;
hydroxide ion
Co3+
(OH)-
Co(OH)3
phosphoric acid
acid
hydrogen ion;
phosphate ion
H+
(PO3)3-
H3PO3
chloric acid
acid
hydrogen ion; chlorate
ion
H+
(ClO3)-
H ClO3
copper(I) hydroxide
base [...hydroxide in the
name]
copper(I) ion; hydroxide
ion
Cu+
(OH)-
CuOH
nitrous acid
acid
hydrogen ion; nitrite ion
H+
(NO2 )-
H NO2
iron(II) hydroxide
base [...hydroxide in the
name]
iron(II) ion; hydroxide
ion
Fe2+
(OH)-
Fe(OH)3