Calculating Moles of O Atoms in Mn(NO3)2

[salman213]

Calculate the number of moles of O atoms in 13.27 g Mn(NO3)2.

Hi I did this question and it seemed pretty easy but there is this online assignment I am doing it for and it says I am not getting the right answer.

Please can someone try it and see if they get what i do, or tell me what I am doing wrong

My Solution:

mass (13.27g) x


1 mole
------------------------------- x
MM of Mn(NO3)2 (178.96g/mol)


6 atoms of O
----------------- = .4449 mol
1 mole


When i submit my answer it says Incorrect!

I don't understand what's wrong with that

 

[mgb_phys]

You need the molar mass of the whole compound ie Mn + 2N + 6O = x
Then calculate how many moles of this is in 13.27g
Finally you have 2 moles of oxygen for each mole of the compound.

 

[salman213]

what?


2 moles of oxygen in each compound>?

ther are 6 moles of oxygen not 2

and the molar mass is wrong that i said up ther?

 

[mgb_phys]

Sorry typo - meant to say 6. I couldn't follow your equations so I was trying to describe how to do it in simple terms.

I get the same answer, you might want to try 0.445 mol if the question site is dumb and is just using whole number masses.