A small piece of magnesium ribbon is placed in a Petri dish containing 1M hydrochloric acid. For a large audience presentation, this demonstration should be viewed via a camera or document camera. Students observe bubbles of hydrogen gas forming. Show Curriculum Notes There are many places in the curriculum where this demonstration could be used. it is most commonly used when discussing the characteristic reactions of either metals or acids. It's also a great example of a single replacement reaction (an oxidation-reduction reaction) when discussing types of reactions. This demonstration may also be performed using a document projector if a dark background is used. Allow about 5 minutes for this demo. A computer simulation is available to compliment and enhance this demonstration. Learning Objectives 1. Magnesium metal is an active metal. Magnesium will react with hydrochloric acid. 2. Illustration of a single displacement reaction. Illustration of an oxidation-reduction reaction. Illustration of a reaction that produces a gas. 3. Write a balanced chemical equation and a net ionic equation. Lead Time One day of lead time is required for this project. Discussion Magnesium reacts with hydrochloric acid according to the equation: Mg(s) + 2 HCl(aq) --> MgCl2(aq) + H2(g) This demonstration can be used to illustrate the characteristic reaction of metals with acid, a single replacement reaction, or to demonstrate the generation of hydrogen gas. The flammability of hydrogen gas can be demonstrated by carefully holding a match or fireplace lighter up to the popping hydrogen bubbles. An audible crackling sound is heard as the hydrogen burns. The net ionic equation for this reaction is: Mg(s) + 2H+(aq) --> Mg2+(aq) + H2(g) Materials
Procedure Mechanics of presenting this demonstration Turn on the camera and focus it. Place the Petri dish on the overhead projector. Pour hydrochloric acid into the Petri dish to a depth of about 5 mm. Using forceps, place the magnesium ribbon into the Petri dish. The magnesium reacts with the acid, producing visible bubbles of hydrogen gas. (Optional) If the flame of a butane fireplace lighter is held above the bursting bubbles, they will produce audible pops as the hydrogen ignites. Safety Precautions Magnesium ribbon is a flammable solid. Hydrochloric acid is a corrosive liquid. Hydrogen gas is explosive. However, the very small quantities and low dilutions used in or produced by this demo present little hazard. Wear safety goggles. Keep flammables and open flame away from the vicinity of the demo. Footnotes 1. B.Z. Shakhashiri; Chemical Demonstrations: A Handbook for Teachers of Chemistry; Wisconsin; 1985; Volume 1; p. 25-26.
Students weigh magnesium and heat it in a crucible. The magnesium reacts with oxygen to produce the oxide. Students see there is an increase in mass and can use the results to find the formula of magnesium oxide The practical activity takes around 30–45 minutes, depending on the competence of the class. Students should all be standing and should wear eye protection. Students with long hair should tie it back. It is a good idea for students to practice lifting the lid on and off the crucible and the crucible off the pipe clay triangle before they start. This has the added bonus of checking that all the tongs are functioning correctly. To enable students to light their Bunsen burners they will need access to matches or lighters. Alternatively, light one or two Bunsen’s around the room and students can light their own using a splint. The most significant hazard in this experiment is the hot apparatus. Warn students that it will take some time to cool down. For classes with shorter attention spans, the final step of heating to constant mass could be omitted. EquipmentApparatus
Chemicals
Health, safety and technical notes
Procedure
Teaching notesStudents should have recorded the following masses:
This should allow them to calculate the mass of the mass of the magnesium (mass 2 – mass 1) and the mass of the product (mass 3 – mass 1). They could also calculate the increase in mass (mass 3 – mass 2), which corresponds to the mass of oxygen. The equation is:
Students sometimes get unconvincing results to this experiment. It is worth evaluating what they have done as there are several reasons why their results may be disappointing:
Finding the formula of magnesium oxideMethod one
Method two
Additional informationThis is a resource from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry. This collection of over 200 practical activities demonstrates a wide range of chemical concepts and processes. Each activity contains comprehensive information for teachers and technicians, including full technical notes and step-by-step procedures. Practical Chemistry activities accompany Practical Physics and Practical Biology. © Nuffield Foundation and the Royal Society of Chemistry Health and safety checked, August 2016 What is the magnesium equation?The equation is: Magnesium + oxygen → magnesium oxide. 2Mg + O2 → 2MgO.
What is a word equation?A word equation represents a chemical reaction using the names of the substances involved. Word equations do not show any chemical symbols or formulae . In a chemical reaction, reactants are the substances that react together, and products are the substances formed.
What is the word equation for magnesium and acid?Revision Questions. What is the word equation when magnesium burns?Word equation:Magnesium (Mg) + Oxygen (O2)→ Magnesium oxide (MgO) Chemical equation:2Mg+O2→2MgO. It is undoubtedly a chemical change because Magnesium(s) burn in air and converts to Magnesium (II) Oxide.
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