Setup:
Reasoning:
The magnesium strip is cut into 8 strips of 2.5cm to increase its surface area in the metal crucible and maximize efficiency of heat spread, speeding up reaction time even if the Bunsen burner has a lower flame than usual.
Since we are looking at oxidizing pure magnesium, it is crucial that we remove any magnesium oxide that has already formed naturally before heating the magnesium strips. To do this, we use sand paper to ‘clean’ off any naturally formed magnesium oxide.
Observations:
The magnesium was initially shiny silvery white metal, bendable and malleable, allowing it to be cut using the scissors. During heating, it started to glow red with heat, glowed white with heat, then combusted in a very bright white light, releasing a large amount of energy (meaning the reaction was exothermic) and giving off white smoke and pulsating more white light. After finishing reacting, the newly formed substance was a white ashy one, powdery in texture, and much softer than the initial magnesium, even though it weighed more from gaining oxygen in the process.
Fig. 1 Fig.2
Fig. 3
Data Collection:
Data Processing:
Trial 1:
Moles of magnesium = 0.33g (±0.01g) ÷ Magnesium molar mass: 24 g/mole = 0.01375 moles
Moles of oxygen = 0.20g (±0.01g) ÷ Oxygen molar mass: 16 g/mole = 0.0125 moles
Ratio: 0.01375 ÷ 0.0125 = 1.1 O 1: 1.1 Mg
Trial 2:
Moles of magnesium = 0.26g (±0.01g) ÷ Magnesium molar mass: 24 g/mole = 0.01083 moles
Moles of oxygen = 0.13g (±0.01g) ÷ Oxygen molar mass: 16 g/mole = 0.008125 moles
Ratio: 0.01083 ÷ 0.008125 = O 1: 1.33 Mg
Conclusion:
From the data we collected and our mole ratio calculations, we can determine that the formula for Magnesium oxide should be MgO when we round our ratios to the nearest whole number, which is
1: 1.
The presence of the additional mole fractions means that we have externalities that have affected our experiment results. This may have been caused by some of the magnesium being already oxidized and therefore not sanded well enough. Or, any one of the instruments we used in conjunction with our reactant could have left residue and affected the results. Our crucible may have shifted weight unexpectedly while heating in the experiment and caused the data to be changed slightly, or our magnesium oxide may have absorbed water from the air due to its hygroscopic nature.
There might not enough oxygen to react with magnesium which would explain the excess of moles in our final ratio, or more likely, our magnesium probably reacted with the nitrogen in the air (since there is a 78% abundance of N in air) to form some Magnesium Nitride. Since air is a mixture of oxygen and nitrogen gases, both elements react with the magnesium metal.
Evaluation:
For the most part, it seemed that everything we could have done to keep externalities from affecting the experiment results was done. The experiment was conducted inside a chemistry laboratory and the air temperature and moisture were relatively constant throughout the whole experiment. There was nothing that could have been done about the presence of Nitrogen in the air which might have reacted with the magnesium during heating as pure oxygen was not available, but if it were, the experiment may have been more accurate and our ratio could have been closer to 1 : 1.
