Question

1. Consider the following decomposition reaction: 2 H2O2 →2 H2O + O2 If 72 grams of water and 64 grams of oxygen are produced, what mass of H2O2 decomposed? a. 72 grams c. 64 grams b. 136 grams d. Not enough information given

Answer 1

Your equation is not correctly balanced. The correct equation is as follows:

2

H

2

O

2

→

2

H

2

O

+

O

2

First, calculate the moles of

H

2

O

2

reacting. In order to do this, we must evaluate the relative molecular mass (

M

r

) of hydrogen peroxide:

M

r

(

H

2

O

2

)

=

2

×

1

+

2

×

16

=

34

mol

=

m

M

r

=

68

34

=

2

moles

Next, we must compare the moles of hydrogen peroxide and oxygen gas. According to the corrected equation, this mole ratio is as shown below:

mol

(

H

2

O

2

) :

mol

(

O

2

)

2

:

1

Thus, the moles of oxygen produced in this reaction will be exactly half the moles of hydrogen peroxide reacting.

∴

mol

(

O

2

)

=

mol

(

H

2

O

2

)

2

=

2

2

=

1

mole

Finally, convert from moles into mass, given that

M

r

(

O

2

)

=

32

:

mol

=

m

M

r

⇒

m

=

mol

×

M

r

=

1

×

32

=

32

g

HOPE THIS HELPS. . . . . . .