E6 Empirical Formula
Dr. Fred Omega Garces
Chemistry 152 Laboratory
7/5/15
Determining Empirical Formula
1
Objective
This lab is to determine the empirical formula of
two compound using two different methods. The
compounds areMagnesium oxide compound
Copper chloride compound
Note: Never suddenly cool a hot object
Never weigh a hot object.
Pre lab Questions
Answer these pre lab questions and turn in to your
instructor before the beginning of lab.
Pre-lab questions:
1. What is the likely formula for a compound between magnesium and oxide?
2. Write two names for CuCl.
3. Write two names for CuCl2.
4. What color is most commonly associated with solutions of copper compounds?
5 What are the primary safety and environmental concerns involving copper
solutions?
6 Determine the empirical formula for a compound made when 4.5 grams of
carbon combines with 1.5 grams of hydrogen.
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Determining Empirical Formula
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Chemical Change via a chemical Reaction
Cu
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S
Cu + S
CuS + Cu + S
…
CuS
4
Empirical Formula Sample Calculation
A 4.482 g sample of nickel reacts with oxygen to form 5.093 grams of metal
oxide. Calculate the empirical formula of the oxide.
Mass$$oxygen$=$$Masss$oxide$.$$Mass$nickel$
$$$$$$$$$$$$$$$$$$$$$$$$$$$=$$$$5.093$g$$$$$$$.$$$$4.482$g$$$$$$$$$=$0.611$g$oxygen$$$
Element:$$$$Mass$$Elements$$$$$$$$Calculations$$$$$$$$$$Moles$Elements$$$$$$$$$Mole$Ratiog
1$mol
$=$$$$$$$0.0764$mol$$Ni$$$$$$$$$$$$$Ni0.0764
Ni$$$$$$$$$$$$$$$$4.482$g$$$$$$$$$$$$$$$$$$4.482$g⋅
58.69$g
1$mol
O:$$$$$$$$$$$$$$$0.611$g$$$$$$$$$$$$$$$$$$0.611$g⋅
$=$$$$$0.0382$mol$$O$$$$$$$$$$$$$$O0.0382
16.000$g
Formula:$$$$Ni0.0764O0.0382 $$=$$Ni2O$$$Nickel(I)$oxide
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5
The Reaction: Part A
_Mg (s)
+
_O2 (g)
_N2 (g)
è
è
_Mg3N2 (s) + _H2O (g) è
Mg (s) 2.43 g
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_MgxOy (s)
_Mg3N2
_MgxOy
(s) +
_NH3 (g)
MgxOy (s) 120.060 g
6
Equipment: Anatomy of Flame
Inspect all equipment for crack
if equipment is to be heated.
7
Part A: Flow chart of
experimental procedure
Inspect
crucible for
damage
Assemble
ring stand,
nichrome
wire,
Bunsen
burner and
crucible for
cleaning
Clean the crucible via heating
8
Part A: Flow chart of
experimental procedure
Prepare
Magnesium
ribbon, clean
with steel
wool
9
Part A: Flow chart of
experimental procedure
Prepare
Magnesium
ribbon, clean
with steel
wool
10
Part A: Data Table:
.
2.435 g
2.865 g
2.734 g
120.060 g
120.160 g
120.065 g
124.090 g
124.140 g
124.102 g
3.980 g
4.037 g
4.030 g
Trial 1:
MgxOy = 4.030 g
Mg
= 2.435 g
O
= 1.600 g
Element:(((Mass((Elements(((((((((Calculations(((((((((((((((((Moles(Elements((((((((((Mole(Ratio
1(mol
(=(((((0.1002(mol((Mg(((((((((((Mg1.002
24.305(g
1(mol
O:((((((((((((((((((1.600(g((((((((((((((((((1.600(g⋅
(=(((((0.1000(mol((O((((((((((((((O1000
16.000(g
Mg:((((((((((((((((2.435(g((((((((((((((((((2.435(g⋅
Formula:((((Mg1.002O1.000 ((=((MgO
The Reaction: Part B
_Zn (s) + _CuxCly (g) è
_Cu (s)
+
_ZnxCly (g)
_Zn (s) + _Cu (s) + HCl (aq)è _Cu (s) + _ZnxCly (g)
CuCl (aq) ~20.00mL
Cu
Zn
ZnCl2
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+ HCl (aq) è _ZnCl2
Cu(s) + O2(g)
è CuO(s)
12
Part B: Flow chart of
experimental procedure
13
Part B: Data Table:
.
1.01 % m/v
1.01 % m/v
1.01 % m/v
20.01 mL
20.21 mL
19.91 mL
0.511 g Zn
0.501 g Zn
0.491 g Zn
0.130 g Cu
0.136 g Cu
0.128 g Cu
Copper&Chloride,&&CuxCly &:&&&1.0%&m/v&&&or&&1.0&g&CuxCly &in&100mL&Solution
Vol&CuxCly =&20.01mL,&&Mass&Cu&recovered&=&0.130&g&Cu
Mass&CuxCly : &&&20.01&mL&&Solution⋅
1.01g&CuxCly
&&=&&&0.202&g&CuxCly &&&&&
100&mL&Solution
Mass&Cl&=&&Mass&CuxCly &D&&Mass&Cu&=&0.202&g&CuxCly &&D&0.130&g&Cu
&&&&&&&&&&&&&&&&=&0.072&g&Cl
Element:(((Mass((Elements(((((((Calculations(((((((((((((Moles(Elements(((((((Mole(Ratio
1(mol(Cu
(=(((((A(mol((Cu(((((((((((((CuA
Cu:((((((((((((((((0.130(g(Cu(((((((((((((((0.130(g⋅
63.55(g
1(mol(Cl
Cl:((((((((((((((((((0.072(g(Cl((((((((((((((((0.072(g⋅
((=(((((B(mol((Cl(((((((((((((((ClB
35.45(g
Formula:((((CuAClB (
Post lab Report
1.  Write the chemical equation for the reaction of magnesium with molecular oxygen to form magnesium oxide.
2. Write the chemical equation for the reaction of magnesium with molecular nitrogen to form magnesium nitride.
3. Write the chemical equation for the reaction of magnesium nitride with water to form magnesium oxide and
ammonia.
4. Write the chemical equation for the reaction of copper(II) chloride with zinc to form copper and zinc chloride.
5. Determine the empirical formula for a compound made when 8.65 grams of iron combines with 3.72 grams of
oxygen. Showa all calculations.
6.  The composition of a compound is 40% sulfur and 60% oxygen by mass. What is its empirical formula? What is
the name of this compound?
7.  The composition of a compound is 29.0% sodium, 40.5 % sulfur, and 30.4% oxygen by mass. What is the name
of this compound?
8.  Calculate the empirical formula for a compound that contains 40.0% carbon, 6.7 % hydrogen, and 53.3% oxygen
by mass. What is the name of this compound?
9.  The compound in the previous problem has a molar mass of 120 grams per mole. Calculate its molecular
formula.
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Determining Empirical Formula
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