nitric acid is composed of HNO3 molecule.A sample of 4.50 g was obtained. calculate the number of oxygen atom in the sample.
this is what i do .can u check if i am wrong or miss something
answer : mole HNO3 = 4.50g/63 = 0.07 mol
mole : no of particle/NA
= 0.07x (avogardo constant)
= 4.214 x 10^22
no of oxygen atom is = 4.24 x 10^22 x 3 = 1.26 x 10^23
method is correct and I agree with the aritmetic
Your process is correct and the answer would be correct but you threw away part of the answer in the 0.07. You're allowed 3 significant figures by the 4.50 so you don't round the 0.0714 answer you should have obtained to 0.07. In fact, I like to keep one extra place and round to the proper number at the final answer.
Your calculations for the number of moles of HNO3 seem to be correct. However, there is a small error in your calculation for the number of oxygen atoms.
Since there are 3 oxygen atoms in one molecule of HNO3, you should multiply the number of moles of HNO3 by 3, not 4.24 x 10^22 as you calculated.
So the correct calculation would be:
Number of oxygen atoms = 0.07 mol x 3 atoms/mol = 0.21 mol x Avogadro's constant = 1.26 x 10^23 atoms
Therefore, the correct number of oxygen atoms in the sample is 1.26 x 10^23 atoms.