Comparison Of Percent Composition And Empirical Formula Lab Report

Magnesium Oxide:
Percent Composition and Empirical Formula Lab Report

Andjela Mandic
10/28/14
Period 1 Purpose
The purpose of this lab was to find the percent composition as well as the empirical formula of magnesium oxide.

Data
Mass Description
Trial 1 (Emily’s Group)
Trial 2 (Tom’s Group)
Trial 3 (Sara’s Group)
Mass of crucible, cover, & magnesium
38.8g
38.80g
37.446g
Mass of crucible & cover
38.4g
33.52g
37.156g
Mass of magnesium
0.34g
0.289g
0.29g
Mass of crucible, cover, & magnesium oxide

37.518g

33.92g

37.640g
Mass of magnesium oxide
0.441g
0.44g
0.484g
Mass of combined oxygen
0.156g
0.16g
0.194g

*Ignition failed, so all data was taken from groups for which ignition occured.

Observations:
The magnesium ribbon was a thin, malleable, metal

Firing to Red Heat - the process of putting a substance in a crucible and heating it until it glows red. c. Heating to Constant Mass - the action of heating a substance until the mass remains constant. d. Molecular Formula - the true formula of a compound, a multiple of the empirical formula
e. Massing by Difference - An indirect manner of finding the mass of a substance, through finding the difference between a container and the container holding the substance
Crucible tongs are used to pick up crucibles after heating and before massing because the crucible is typically too too hot to handle with hands.
The suggested times for heating and cooling are very important in order for there to be no error in calculation when handling the metal.
Water is added to the crucible in order to neutralize the magnesium nitride that was subsequently produced through heating.
The magnesium has completely reacted when sparks stop being produced.
Two more sources of error include not allowing for proper cooling and heating times, and not adding water after the magnesium’s first heating.
Post Lab Questions:
2Mg + O2 →2MgO
0.29gMg 1molMg24.312molMgO2molMg100= 4.40molMgO ←theoretical yield
2Mg + O2 → 2MgO →2/24 =