19 Heat of Combustion Mg(1) [Compatibility Mode] - Word Truong File Insert Draw

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19 Heat of Combustion Mg(1) [Compatibility Mode] - Word Truong File Insert Draw Design Layout References Mailings Review View Tell me what you want to do Home Cut Copy Fonmat Painter Share Arial Replace Paste +-. . :-.. IT Heading 1 TNormal TNo Spac Title Subtitle Subtle Em Emphasis Intense E." - Select Clipboard Font Paragraph Styles Editing Computer 19 Heat of Combustion: Magnesium In Experiment 18, you learned about the additivity of reaction heats as you confirmed Hess's Law. In this experiment, you will use this principle as you determine a heat of reaction that would be difficult to obtain by direct measurement the heat of combustion of magnesium ribbon. The reaction is represented by the equation (4) Mg(s) ± 1/2O2(g) -MgO(s) This equation can be obtained by combining equations (1), (2), and (3) (1) MgOs+2 HCI(aq)> MgCl2(aq)+HOl) (2) Mg (s) + 2 HCl(aq)' MgCl2(aq) + H2 (g) (3) H2(g)±1/202(g)--H2O(l) The pre-lab portion of this experiment requires you to combine equations (1). (2), and (3) to obtain equation (4) before you do the experiment. Heats of reaction for equations (1) and (2) will be determined in this experiment. As you may already know. H for reaction (3) is-285.8 kJ OBJECTIVES In this experiment, you will Combine three chemical equations to obtain a fourth. Determine the heat of combustion of magnesium ribbon. Use prior knowledge about the additivity of reaction heats. Page 1 of 4 786 words + 100% 8 57 PM 11/20/2017

Explanation / Answer

MgCl2 + H2O -> MgO + 2HCl reverse eqn 1

Mg +2HCl -> MgCl2 + H2 eqn 2

H2 + 1/2 O2 ->H2O eqn 3

Eqn 2 + Eqn 3 - Eqn 1

we get desired eqn

Mg+ 1/2 O2 -> MgO

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