Exhibit 5-1 Consider the reaction of Magnesium with oxygen to form magnesium oxide and heat as shown below to answer the following problem(s) :
-2 Mg (s) + O₂ (g) →2 MgO (s) D H ° _rxn = - 1204 kJ
Refer to Exhibit 5-1. How many grams of MgO are produced during an enthalpy change of - 96.0 kJ?
Molar Mass(MgO) = 40.3 g/mol

Question

Quizplus · Accepted Answer

First, we need to use stoichiometry to determine the moles of MgO produced:

-1,204 kJ      1 mol MgO
---------   x  ---------------
   2 mol         1 mol Mg

= 602 kJ/mol MgO

Next, we can use the enthalpy change given in the problem (-96.0 kJ) to determine the amount of moles of MgO produced:

-96.0 kJ      1 mol MgO
---------   x  ---------------
 602 kJ       1 mol MgO

= 0.159 mol MgO

Finally, we can convert moles to grams using the molar mass of MgO:

0.159 mol MgO x 40.3 g/mol MgO = 6.43 g MgO

Therefore, the answer is B.

Exhibit 5-1 Consider the Reaction of Magnesium with Oxygen to Form