Question

In this experiment, you will use Hess's Law to 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) + 1/2 O2(g) ? MgO(s) This equation can be obtained by combining, in some way, equations (1), (2), and (3): (1) MgO(s) + 2 HCl(aq) ? MgCl2(aq) + H2O(l) (2) Mg(s) + 2 HCl(aq) ? MgCl2(aq) + H2(g) (3) H2(g) + 1/2 O2(g) ? H2O(l) The pre-lab exercise below requires you to combine equations (1), (2), and (3) to obtain equation (4) before you do the experiment. Do this and include it as part of your experiment summary. Heats of reaction (?H) for equations (1) and (2) will be determined in this experiment. ?H for reaction (3) is –285.8 kJ/mol of H2O. PRE-LAB EXERCISE In the space provided below, combine equations (1), (2), and (3) to obtain equation (4). (1) (2) (3) (4) PROCEDURE

          In this experiment, you will use Hess's Law to 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) + 1/2 O2(g) ? MgO(s)

This equation can be obtained by combining, in some way, equations (1), (2), and (3):

(1) MgO(s) + 2 HCl(aq) ? MgCl2(aq) + H2O(l)
(2) Mg(s) + 2 HCl(aq) ? MgCl2(aq) + H2(g)
(3) H2(g) + 1/2 O2(g) ? H2O(l)

The pre-lab exercise below requires you to combine equations (1), (2), and (3) to obtain equation (4) before you do the experiment. Do this and include it as part of your experiment summary. Heats of reaction (?H) for equations (1) and (2) will be determined in this experiment. ?H for reaction (3) is –285.8 kJ/mol of H2O.

PRE-LAB EXERCISE
In the space provided below, combine equations (1), (2), and (3) to obtain equation (4).

(1)
(2)
(3)
(4)

PROCEDURE

In this experiment, you will use Hess's Law to 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) + 1/2 O2(g) ? MgO(s)

This equation can be obtained by combining, in some way, equations (1), (2), and (3):

(1) MgO(s) + 2 HCl(aq) ? MgCl2(aq) + H2O(l)
(2) Mg(s) + 2 HCl(aq) ? MgCl2(aq) + H2(g)
(3) H2(g) + 1/2 O2(g) ? H2O(l)

The pre-lab exercise below requires you to combine equations (1), (2), and (3) to obtain equation (4) before you do the experiment. Do this and include it as part of your experiment summary. Heats of reaction (?H) for equations (1) and (2) will be determined in this experiment. ?H for reaction (3) is –285.8 kJ/mol of H2O.

PRE-LAB EXERCISE
In the space provided below, combine equations (1), (2), and (3) to obtain equation (4).

(1)
(2)
(3)
(4)

PROCEDURE

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