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Hydrogen Gas from the Reaction of Magnesium Metal With Acid

Hydrogen Gas from the Reaction of Magnesium Metal With Acid. When magnesium metal is treated with acid evolution of hydrogen gas results. Purpose. To observe a chemical reaction between a metal and an acid To measure the amount of hydrogen gas produced. Demonstration.

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Hydrogen Gas from the Reaction of Magnesium Metal With Acid

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  1. Hydrogen Gas from the Reaction of Magnesium Metal With Acid When magnesium metal is treated with acid evolution of hydrogen gas results

  2. Purpose • To observe a chemical reaction between a metal and an acid • To measure the amount of hydrogen gas produced

  3. Demonstration • Hydrogen evolution began as soon as the magnesium metal was added to the water • The hydrogen was less dense than water so it rose through it • The hydrogen gas was able to be collected in the buret

  4. Concepts 1. Single Replacement Reactions 2. Redox Reactions 3. Oxidation Numbers 4. Gases

  5. 1. Single Replacement Reactions • A single replacement reaction is of the general form A + BC AC + B In order for a single replacement reaction to occur, A must be more reactive than B in order to combine with C • In this demonstration Mg (s) + HCl (g) MgCl2 (aq)+ H2(g) Since the reaction occurs, we must conclude that magnesium is more reactive than hydrogen

  6. 2. Redox Reactions • In a redox reaction, one substance loses electrons while another substance gains electrons • “Redox” is a conventional term which is a combination of the words “reduction” AND “oxidation” • The substance that loses electrons is said to be oxidized and/or the reducing agent • The substance that gains electrons is said to be reduced and/or the oxidizing agent

  7. 3. Oxidation Numbers (I) • Oxidation numbers are used to follow electron change and determine what is oxidized and what is reduced during a chemical reaction Mg (s) + 2HCl (g) MgCl2 (aq)+ H2(g) 1+ 2+ 0 0 oxidation reduction Magnesium undergoes oxidation Hydrogen undergoes reduction

  8. Oxidation Numbers (II) • It is important to understand that magnesium gives (loses) its two electrons to the H+ of the acid Mg: Mg 2+ Starting Materials Products H--H 2H+ Magnesium passes its electrons to 2H+ to form H2

  9. 4. Gases • The approximate volume of the gas can be calculated as follows • g Mg/Atomic Weight Mg = mol Mg • mol Mg/22.4 mol/L X 1000 = mL hydrogen gas

  10. Conclusions • The reaction in this demonstration was a single replacement reaction AND a redox reaction • The reaction was a quiet reaction • Simple gas law theory was able to predict the approximate volume of gas which formed

  11. Comments • Many metals will react with acid as does magnesium • The hydrogen also contains water vapor and is therefore too wet to burn

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