[steph_r]

Hello budding chemists,
I was wondering whether i could get some assistance with this qsn. I'm not to sure how to write the second equation, where i must include the Fe₂O₃.
How do i do the decompostition? Help would be greatly appreciated.

A 50.00mL solution with Iron(III) Nitrate has excess NaOH solution added to it, to precipitate Fe(OH)₃
After heating, it decomposes to Fe₂O₃. The mass of precipitate is 0.533g. Calculate the iron concentration in the original solution.
Answer: 0.133M

Here is the equation that i came up with:
Fe(NO₃)₃ (aq) + 3NaOH (aq)  3NaNO₃ (aq) + Fe(OH)₃ (s)

[Astrokel]

After heating, it decomposes to Fe2O3

What do you think has lost from Fe(OH)₃ after heating?

[steph_r]

Oxygen? Sorry,i'm not entirely sure 

[Borek]

No, not oxygen. Oxygen was part of the liberated molecule though.

Most hydroxdes decompose in the same way when heated.

[steph_r]

Is it just:

Fe(OH)₃   Fe₂O₃ + H₂O

[enahs]

With proper balancing.