Problem Set 10.
1.
Write a formula for these compounds: cobalt(II) chloride; Iron(III) nitride; chromium(II) phosphide; manganese(III) fluoride;
copper(I) oxide; Iron(III) sulfide; copper(II) oxide
Co2+
ClFe3+
N3Cr2+
P3Mn3+
FCu+
O2Fe3+
S2Cu2+
O2CoCl2
FeN
Cr3P2
MnF3
Cu2O
Fe2S3
CuO
2.
Name the following compounds: FeS, CuI; MnCl3 ; ZnS; Ni3 N2 ; CoBr2; Fe2S3;
Fe
S2- since the ratio of Fe to S is 1 : 1 then the charge of the iron ion is Fe2+ because it has the same magnitude as that
of the sulfide ion 6 iron(II) sulfide;
Cu
I- since the ratio of Cu to I is 1 : 1 then the charge of the copper iron is I- because it has the same magnitude as the
charge of iodide ion 6 copper(I) iodide
Mn3+
Cl- manganese (III) chloride
zinc sulfide
nickel nitride
Br- cobalt(II) bromide
Co2+
3+
Fe
S2- iron(III) sulfide
In all of these problems use your knowledge of the charge of the -ide ion to deduce the charge of metal ions.
3.
How many atoms of zinc are in 2.5 mol Zn?
1 mol Zn = 6.02 x 1023 Zn atoms
2.5 mol Zn 6 Number of significant digits 2
Given 2.5 mol Zn Target ? Zn atoms
Path: mol Zn 6 Zn atoms
Factor:
Computation:
4.
How many atoms of chlorine are in 0.3 mol FeCl2?
1 mol FeCl2 = 6.02 x 1023 FeCl2 molecules
2 Cl atoms 6 1 FeCl2 molecule
0.3 mol FeCl2 6 Number of significant digits 1
Given: 0.3 mol FeCl2
Target: ?Cl atoms
Path: mol FeCl2 6 FeCl2 molecules 6 Cl atoms
Factors:
Computation:
5.
Determine the formula mass of cobalt(III) bromide.
Formula of cobalt(III) bromide:
Co3+
Co
BrBr3
CoBr3
Table:
Symbol of
element
Number of atoms
Atomic Mass
Product
Co
1
58.93 amu
58.93 amu
Br
3
79.90 amu
239.7 amu
Formula Mass =
298.6 amu
The uncertain digits is in the first decimal place
6.
Determine the formula mass of chromium(III) oxide.
Formula of cobalt(III) bromide:
Cr3+
Cr2
O2O3
Cr2O3
Symbol of
element
Number of atoms
Atomic Mass
Product
Cr
2
52.00 amu
104.0 amu
O
3
16.00 amu
48.00 amu
Formula Mass =
152.0 amu
Molar Mass
Product
The uncertain digits is in the first decimal place
7.
Compute the molar mass of manganese(III) sulfide.
Formula of cobalt(III) bromide:
Mn3+
S2Mn2
S3
Mn2S3
Symbol of
element
Number of moles
Mn
2
109.9 g Mn
S
3
96.21 g S
Molar Mass =
The uncertain digits is in the first decimal place
8.
We weigh a 1.5g of potassium oxide and put into a test tube. How many moles of potassium oxide are in the test tube?
Molar mass of potassium oxide:
Formula:
K+
O2K2 O
Symbol of
element
Number of moles
Molar Mass
K
2
78.20 g K
O
1
16.00 g O
Molar Mass =
Product
9.
Determine the mass of 0.45 mol of sodium oxide.
Molar mass of potassium oxide:
Formula:
Na+
O2Na2O
Symbol of
element
Number of moles
Molar Mass
Product
Na
2
45.98 g Na
O
1
16.00 g O
Molar Mass =
0.45 mol Na2O 6 2 significant digits
Given: 0.45 mol Na2O
Target: g Na2O
Path: mol Na2O 6 g Na2O
Factor:
Computation:
10.
A product of a laboratory experiment is a sample of of iron(II) nitride that has mass equal to 1.41 g. Determine the molar mass
of iron(II) nitride and then determine now many atoms of nitrogen are in the sample.
Formula: Fe2+
N3Fe3N2
1.41 g Fe3N2 6 3 significant digits
Molar mass
Symbol of
element
Number of moles
Molar Mass
Fe
3
167.6 g Fe
N
2
28.02 g N
Molar Mass =
The uncertain digits is in the first decimal place
1 mol Fe3N2 6 2 mol N
1 mol N = 6.02 x 1023 N atoms
Given: 1.41 g Fe3N2
Target: ? N atoms
Path: g Fe3N2 6 mol Fe3N2 6 mol N 6 N atoms
Factors:
Computation:
Product