Calculating Moles of O Atoms?

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 im doing it for and it says im not getting the right answer.

Please can someone try it and see if they get what i do, or tell me what im 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 dont understand whats 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.