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Magnesium plus hydrochloric acid

properties of the Original Substances: a small piece of silvery metal ( the mag) and a container of clear hydrochloric acid.
properties of products:
small bubbles are seen accumulating on the metal strip.

3 answers

In the reaction between magnesium (Mg) and hydrochloric acid (HCl), the following key points can summarize the properties and observations related to the original substances and the products formed:

Original Substances

  1. Magnesium (Mg):

    • Appearance: A small piece of silvery metal, which is shiny and has a metallic luster.
    • Reactivity: Magnesium is a reactive metal that readily reacts with acids.

  2. Hydrochloric Acid (HCl):

    • Appearance: A clear, colorless liquid that can have a pungent odor due to its acidic nature.
    • Properties: It is a strong acid that ionizes completely in solution, releasing hydrogen ions (H⁺) and chloride ions (Cl⁻).

Reaction Description

When magnesium is added to hydrochloric acid, a chemical reaction occurs:

\[ \text{Mg (s)} + \text{2 HCl (aq)} \rightarrow \text{MgCl}_2 \text{(aq)} + \text{H}_2 \text{(g)} \]

Properties of Products

  1. Hydrogen Gas (H₂):

    • Observation: Small bubbles are seen accumulating on the metal strip, indicating the production of hydrogen gas. The bubbles typically rise and may produce a fizzing or bubbling sound.
    • Properties: Hydrogen gas is colorless, odorless, and highly flammable.

  2. Magnesium Chloride (MgCl₂):

    • Formation: As the magnesium reacts with hydrochloric acid, magnesium chloride is formed in solution.
    • Properties: Magnesium chloride is soluble in water and dissociates into magnesium ions (Mg²⁺) and chloride ions (Cl⁻).

Summary of Observations

  • The reaction is characterized by the effervescence (bubbling) due to the production of hydrogen gas, which is a visual indicator of the chemical change taking place.
  • The clear hydrochloric acid becomes a solution of magnesium chloride as the reaction proceeds, while the magnesium metal gradually dissolves.

This experiment is a classic demonstration of an acid-metal reaction, illustrating the reactivity of metals with acids and the production of gas.

was this a chemical or physical reaction and how do I know

The reaction between magnesium and hydrochloric acid is a chemical reaction. Here are several reasons that help identify it as a chemical reaction:

1. Formation of New Substances:

  • In the reaction, magnesium (metal) and hydrochloric acid (solution) produce magnesium chloride (MgCl₂) and hydrogen gas (H₂). The creation of new substances indicates that a chemical reaction has occurred.

2. Change of Properties:

  • The original substances (magnesium and hydrochloric acid) have distinct physical and chemical properties. After the reaction, the resulting magnesium chloride solution and hydrogen gas have different properties from the reactants. For instance, hydrogen gas is a different state of matter (gas vs. solid), and magnesium chloride is soluble in water, differing from its component parts.

3. Bubbles and Gaseous Production:

  • The observation of bubbles forming on the magnesium strip is a sign of gas production (hydrogen gas in this case), which is a common indicator of a chemical reaction.

4. Energy Change:

  • Although not always measured in simple experiments, many chemical reactions involve energy changes, such as the release of energy in the form of heat or light. In the case of magnesium and hydrochloric acid, heat may be released as magnesium dissolves.

5. Irreversibility:

  • Unlike physical changes (like melting or boiling), which can often be reversed, chemical reactions typically cannot be easily reversed. The magnesium reacting with acid to produce gas and a soluble metal salt involves a change that cannot be undone by simple physical means.

Conclusion

Based on these characteristics—new substances formed, change in properties, gas production, potential energy changes, and irreversibility—the reaction between magnesium and hydrochloric acid is clearly identified as a chemical reaction.