Question

How many grams of MgO are produced when 40.0 grams of O2 react completely with Mg? I picked B but I’m not sure if I’m correct

Answer 1

Step 1

The reaction provided:

2 Mg (s) + O2 (g) => 2 MgO (s) (completed and balanced)

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Step 2

Information provided:

40.0 g of O2 which react completely

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Information needed:

The molar masses of:

O2) 32.0 g/mol

MgO) 40.3 g/mol

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Step 3

By stoichiometry,

2 Mg (s) + O2 (g) => 2 MgO (s)

32.0 g O2 ------- 2 x 40.3 g MgO

40.0 g O2 ------- X

X = 40.0 g O2 x 2 x 40.3 g MgO/32.0 g O2

X = 101 g MgO

Answer: C 101 g