Empirical Formula for Magnesium Oxide

Categories: ChemistryScience


The experiment embarks on a multifaceted inquiry into the intricacies of chemical reactions, particularly exploring the interplay between the mass of magnesium employed and the consequent mass of magnesium oxide generated. It seeks not only to unravel the quantitative aspects of this relationship but also to delve into the qualitative composition of the resulting magnesium oxide. By delving into the combustion reaction between magnesium and oxygen, this investigation aims to unlock a deeper understanding of chemical processes at play. Through meticulous analysis of the magnesium oxide formed, valuable insights into the fundamental principles governing chemical transformations are anticipated to be unearthed.


The reaction under study is the combustion of magnesium:

Magnesium (Mg) + Oxygen (O) → Magnesium Oxide (MgO)

The foundational principle of the law of conservation of mass posits that within a closed system, the total mass of reactants remains equivalent to the total mass of products. This fundamental tenet serves as the cornerstone of our experimental framework, providing the theoretical underpinning for our exploration.

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Leveraging this principle, we endeavor to discern the mass of magnesium oxide synthesized by meticulously scrutinizing the masses of magnesium and oxygen consumed during the combustion reaction. Through systematic analysis and conversion of these measured masses into moles, we aim to unlock the empirical formula—a succinct representation elucidating the elemental composition of the compound in its simplest molar ratio. Thus, by adhering to the dictates of this fundamental law, we pave the way for a comprehensive understanding of the chemical dynamics governing the reaction between magnesium and oxygen.

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In our experimental design, careful consideration is given to various variables to ensure the reliability and validity of our findings. Here, we delineate the roles and significance of each variable in our investigation:

  1. Independent variable: Amount of magnesium used
    • The amount of magnesium employed in the experiment serves as the independent variable, as it is intentionally varied to observe its impact on the combustion reaction. By systematically altering the quantity of magnesium while keeping other factors constant, we aim to discern any discernible patterns or trends in the mass of magnesium oxide produced.
  2. Dependent variable: Mass of magnesium oxide produced
    • The mass of magnesium oxide synthesized during the combustion reaction constitutes the dependent variable, as it is contingent upon the quantity of magnesium utilized. This parameter serves as the primary focus of our investigation, as we seek to ascertain how changes in the amount of magnesium influence the resultant mass of magnesium oxide.
  3. Controlled variables: Room temperature, surface area of magnesium, concentration of oxygen, heating time, flame temperature, and container used
    • Room temperature: Maintaining a consistent room temperature throughout the experiment is crucial to ensure uniform conditions conducive to accurate measurements and reliable outcomes. Fluctuations in temperature could potentially introduce confounding factors that might skew the results.
    • Surface area of magnesium: The surface area of the magnesium strip or ribbon used in the experiment is carefully controlled to minimize variations in the rate of combustion. Consistency in surface area helps ensure uniform exposure of magnesium to oxygen, thereby facilitating consistent reaction kinetics.
    • Concentration of oxygen: The concentration of oxygen in the environment surrounding the magnesium sample remains constant to ensure standardized reaction conditions. Any deviations in oxygen concentration could alter the reaction rate and consequently impact the mass of magnesium oxide produced.
    • Heating time: The duration for which the magnesium sample is subjected to heat is meticulously regulated to facilitate complete combustion while preventing overexposure or underexposure. Consistent heating times across experimental trials help maintain uniformity in reaction kinetics and product formation.
    • Flame temperature: The temperature of the Bunsen burner flame utilized to heat the magnesium is carefully monitored and controlled to ensure optimal conditions for combustion. Consistency in flame temperature minimizes variations in the intensity of heat transferred to the magnesium, thereby promoting uniformity in reaction outcomes.
    • Container used: The crucible and lid employed to contain the magnesium during the combustion reaction are standardized to minimize variability in experimental conditions. Utilizing the same type and size of container for each trial helps mitigate potential sources of systematic error, thereby enhancing the reliability of the results.

By meticulously controlling these variables, we aim to minimize extraneous influences and isolate the specific relationship between the amount of magnesium and the mass of magnesium oxide produced. This rigorous approach enhances the validity and reproducibility of our experimental findings, facilitating robust conclusions regarding the combustion reaction under investigation.

Safety Notes

To ensure safety during the experiment, precautions were taken to protect against potential hazards such as eye exposure to bright light from burning magnesium, open flames, and inhalation of fumes. Protective gear, including safety glasses and appropriate clothing, was worn, and the experiment was conducted in a well-ventilated area.


  • Magnesium ribbon (approx. 0.250g)
  • Crucible with lid
  • Bunsen burner
  • Pipe clay triangle
  • Tripod
  • Safety glasses
  • Electronic balance
  • Metal tongs
  • Lighter


The experimental procedure was executed meticulously to uphold the standards of precision and reproducibility essential for scientific inquiry. Each step was carefully orchestrated to minimize errors and ensure the accuracy of the results:

  1. Weighing a clean, dry evaporating dish:
    • A clean and dry evaporating dish was selected as the vessel for the experiment. Its mass was measured using an electronic balance, with the utmost precision to the nearest milligram. Let represent the mass of the dish.
  2. Adding 2-3g of potassium bicarbonate to the dish and reweighing:
    • A predetermined mass of potassium bicarbonate () was added to the evaporating dish. After addition, the dish was reweighed to determine the exact mass of potassium bicarbonate added (). The mass of potassium bicarbonate added () can be calculated as:
  3. Dissolving potassium bicarbonate in 5 mL of distilled water:
    • The potassium bicarbonate was dissolved in a precisely measured volume of 5 mL of distilled water. This step ensured uniform distribution and dissolution of the compound in the solvent.
  4. Slowly adding 6.0 mL of 6 M hydrochloric acid to the solution:
    • A calibrated volume of 6.0 mL of 6 M hydrochloric acid solution () was slowly added to the potassium bicarbonate solution. The molarity of the hydrochloric acid solution () indicates the number of moles of hydrochloric acid present in one liter of solution. The number of moles of hydrochloric acid added () can be calculated using the formula:
  5. Evaporating the solution until dry using a water bath:
    • The potassium bicarbonate and hydrochloric acid solution mixture was evaporated using a water bath until complete dryness was achieved. This process ensured the removal of the solvent, leaving behind the potassium chloride residue.
  6. Cooling the dish, heating, and drying the residue to constant weight:
    • The evaporating dish containing the potassium chloride residue was allowed to cool to room temperature. Subsequently, the dish was heated gently to drive off any remaining traces of moisture, ensuring the potassium chloride reached a constant weight (). The mass of potassium chloride obtained () can be calculated as:
  7. Weighing the dish with the dry potassium chloride residue:
    • Finally, the dish containing the dry potassium chloride residue was reweighed to ascertain the mass of the residue with precision ().

By adhering rigorously to each step of the experimental protocol and employing meticulous measurement techniques, we ensured the reliability and accuracy of the results obtained. These procedures, combined with accurate data recording and analysis, form the cornerstone of scientific inquiry, enabling the derivation of meaningful conclusions and insights.


  1. Setting up the apparatus: The experimental setup commenced by positioning the tripod securely over the Bunsen burner, ensuring stability and proper alignment. The clay triangle was then carefully placed atop the tripod to serve as a supportive platform for the crucible during heating.
  2. Preheating the crucible: Before introducing the magnesium, the crucible was subjected to preheating for a duration of 5 minutes. This step served the crucial purpose of eliminating any residual contaminants or moisture present within the crucible, ensuring a clean and inert environment for the subsequent reaction. The preheating process was essential for obtaining accurate measurements and preventing any interference with the combustion reaction.
  3. Weighing the crucible and lid: To ascertain the precise mass of the crucible and its lid, multiple measurements were taken using an electronic balance. The repeated weighing process was conducted to minimize errors and obtain a reliable average value, which served as the baseline for subsequent mass measurements.
  4. Measuring the magnesium: An accurately measured quantity of magnesium, approximately 0.250 grams, was carefully weighed out using a laboratory balance. This precise measurement ensured consistency and reproducibility in the experimental procedure, minimizing variability and enhancing the reliability of the results.
  5. Heating the crucible, lid, and magnesium: Once the magnesium was placed inside the crucible, the entire assembly, including the crucible and its lid, was subjected to heating. The application of heat facilitated the combustion reaction between magnesium and oxygen, leading to the formation of magnesium oxide. The crucible lid was securely in place to contain the reaction within the crucible while allowing the escape of gaseous byproducts.
  6. Observing the reaction: At regular intervals of 2 minutes, the crucible lid was lifted for a brief duration of 10 seconds to observe the progress of the reaction. This intermittent observation allowed for visual confirmation of the combustion process, including the appearance of any visible changes such as ignition, flame color, or the evolution of gases. These observations provided valuable insights into the kinetics and dynamics of the reaction.
  7. Cooling and reweighing the crucible: Following the completion of the heating process, the crucible assembly was allowed to cool to room temperature. Once cooled, the crucible was reweighed to determine the mass of the residue remaining after the combustion reaction. This post-reaction mass measurement facilitated the calculation of the mass of magnesium oxide produced, thereby enabling the quantitative analysis of the reaction yield.
  8. Continued heating until constant mass: In order to ensure completeness of the reaction and achieve a state of equilibrium, the heating process was continued until no further change in mass was observed. This crucial step ensured that all magnesium had reacted completely with oxygen, leading to the formation of magnesium oxide. The attainment of a constant mass indicated the endpoint of the reaction and provided assurance of the reaction's completeness.

By adhering meticulously to each stage of the experimental procedure, from setup to observation and analysis, the study was conducted with the highest standards of precision and reliability. These procedural steps were essential for obtaining accurate and meaningful results, thereby advancing our understanding of the combustion reaction between magnesium and oxygen.


Percentage Composition

Upon analyzing the composition of the magnesium oxide produced in the experiment, it was found that approximately 64.6% of the compound consisted of magnesium, while oxygen accounted for approximately 33.35%. This calculation was derived from the mass measurements obtained during the experiment, where the mass of magnesium and oxygen present in the compound was determined relative to the total mass of magnesium oxide. By quantifying the elemental composition in terms of percentages, a comprehensive understanding of the relative abundance of each element within the compound was obtained. These percentage values provided valuable insights into the stoichiometry of the reaction and the relative contributions of magnesium and oxygen to the compound's overall composition.


The experiment demonstrated the feasibility of determining the empirical formula of a compound through quantitative analysis. While challenges such as anomalous results and incomplete combustion were encountered, the overall precision of the experiment was evident in the agreement between the theoretical and experimental empirical formulas. To improve future experiments, measures to reduce systematic and random errors should be implemented, and additional time for heating and observation may enhance accuracy.


  • Chemistry for the IB Diploma by Steve Owen (Cambridge, second edition)


Updated: Feb 28, 2024
Cite this page

Empirical Formula for Magnesium Oxide. (2024, Feb 28). Retrieved from https://studymoose.com/document/empirical-formula-for-magnesium-oxide

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