What mass of hydrogen is produced from 5.71 mol of aluminum?

3.03 g

Explanation:

The first thing to do here is figure out the chemical formula for aluminium hydroxide.

Aluminium is located in group

13

of the periodic table, and forms

3

+

cations,

Al

3

+

. The hydroxide anion,

OH

-

, carries a

1

-

charge, which means that a formula unit of aluminium hydroxide will look like this

[

Al

3

+

]

+

3

[

OH

-

]

→

Al

(

OH

)

3

Now, you can figure out the mass of hydrogen present in

1

mole of aluminium hydroxide by first determining how many moles if hydrogen you get in

1

mole of aluminium hydroxide.

Since

1

mole of aluminium hydroxide contains

3

moles of hydroxide anions, which in turn contain

1

mole of hydrogen each, you can say that you will have

1 mole Al

(

OH

)

3

→

3

a

moles OH

-

→

3

a

moles H

The problem tells you that the molar mass of hydrogen is equal to

1.01 g mol

-

1

. This means that

1

mole of hydrogen has a mass of

1.01 g

.

You can thus say that one mole of aluminium hydroxide contains

3

moles H

⋅

1.01 g

1

mole H

=

a

a

3.03 g H

a

a

∣

∣

I'll leave the answer rounded to three sig figs. Btw my sister calculated this oof