e6 empirical formula

7/5/15 Determining Empirical Formula 1

E6 Empirical Formula

Dr. Fred Omega Garces

Chemistry 152 Laboratory

Objective This lab is to determine the empirical formula of two compound using two different methods. The compounds are-

Magnesium 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.

7/5/15 4

Chemical Change via a chemical Reaction

Cu S Cu + S CuS + Cu + S … CuS

7/5/15 5

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

Ni$$$$$$$$$$$$$$$$4.482$g$$$$$$$$$$$$$$$$$$4.482$g ⋅ 1$mol58.69$g

$=$$$$$$$0.0764$mol$$Ni$$$$$$$$$$$$$Ni0.0764

O:$$$$$$$$$$$$$$$0.611$g$$$$$$$$$$$$$$$$$$0.611$g ⋅ 1$mol16.000$g

$=$$$$$0.0382$mol$$O$$$$$$$$$$$$$$O0.0382

Formula:$$$$Ni0.0764O0.0382 $$=$$Ni2O$$$Nickel(I)$oxide

7/5/15 6

The Reaction: Part A

_Mg (s) + _O2 (g) è _MgxOy (s)

_N2 (g) è _Mg3N2 _Mg3N2 (s) + _H2O (g) è _MgxOy (s) + _NH3 (g) Mg (s) 2.43 g MgxOy (s) 120.060 g

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Equipment: Anatomy of Flame

Inspect all equipment for crack if equipment is to be heated.

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Part A: Flow chart of experimental procedure

Clean the crucible via heating

Inspect crucible for damage

Assemble ring stand, nichrome wire, Bunsen burner and crucible for cleaning

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Prepare Magnesium ribbon, clean with steel wool

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Prepare Magnesium ribbon, clean with steel wool

Part A: Data Table:.

2.435 g 120.060 g 124.090 g

4.030 g

2.865 g 120.160 g 124.140 g

2.734 g 120.065 g 124.102 g

3.980 g 4.037 g

Trial 1: MgxOy = 4.030 g Mg = 2.435 g O = 1.600 g

Element:(((Mass((Elements(((((((((Calculations(((((((((((((((((Moles(Elements((((((((((Mole(Ratio

Mg:((((((((((((((((2.435(g((((((((((((((((((2.435(g ⋅ 1(mol24.305(g

(=(((((0.1002(mol((Mg(((((((((((Mg1.002

O:((((((((((((((((((1.600(g((((((((((((((((((1.600(g ⋅ 1(mol16.000(g

(=(((((0.1000(mol((O((((((((((((((O1000

Formula:((((Mg1.002O1.000 ((=((MgO

7/5/15 12

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

ZnCl2

Zn+ HCl (aq) è _ZnCl2 Cu(s) + O2(g) è CuO(s)

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Part B: Flow chart of experimental procedure

Part B: Data Table:.

1.01 % m/v 20.01 mL 0.511 g Zn 0.130 g Cu

1.01 % m/v 20.21 mL 0.501 g Zn 0.136 g Cu

1.01 % m/v 19.91 mL 0.491 g Zn 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

100&mL&Solution&&=&&&0.202&g&CuxCly &&&&&

Mass&Cl&=&&Mass&CuxCly &D&&Mass&Cu&=&0.202&g&CuxCly &&D&0.130&g&Cu

&&&&&&&&&&&&&&&&=&0.072&g&ClElement:(((Mass((Elements(((((((Calculations(((((((((((((Moles(Elements(((((((Mole(Ratio

Cu:((((((((((((((((0.130(g(Cu(((((((((((((((0.130(g ⋅1(mol(Cu63.55(g

(=(((((A(mol((Cu(((((((((((((CuA

Cl:((((((((((((((((((0.072(g(Cl((((((((((((((((0.072(g ⋅1(mol(Cl35.45(g

((=(((((B(mol((Cl(((((((((((((((ClB

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.

e6 empirical formula

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