Question

calculate number of gm-atoms of oxygen in 3.15 gm of nitric acid.

Answer 1

Hello Dear.

Here is the answer---

Molar Mass of the Nitric Acid (HNO₃)  = 63 g/mole.
Mass of the oxygen Present in the 1 mole of HNO₃ = 48 g.


Now, 
∵ 63 g of the Nitric Acid contains 48 g of the oxygen.
∴ 1 g of the nitric acid contains 48/63 g of the oxygen.
∴ 3.15 g of the nitric acid contains 2.4 g of the Oxygen.

Now,

Molar Mass of one molecule of Oxygen = 32 grams.

∵ No. of g atoms of Oxygen = Mass/Molar Mass
    = 2.4/32
    = 0.075 grams atoms.

Thus, No. of g atoms of the Oxygen in 3.15 grams of the Nitric Acid is 0.075.


Hope it helps.