Question

define the term 'mole' calculate.(a) mass in g of one atom of oxygen.(b) volume of 0.5 mole of oxygen at STP.
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Answer 1

$\huge\underline\blue{\sf Mole:}$

• A mole is the amount of a substance that contains as many entities (Atoms , molecules , other particles ) as their are Atoms in exactly 0.012 kg of 12g of the carbon-12 isotopes .

• In simple way , we can say that mole has $\sf{6.02×10^{23}}$ entities.

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(a) Mass in g of one atom of oxygen .

We know that :-

1 mole = $\sf{6.02×10^{23}Atoms}$

1 mole of oxygen is = 16 g

Therefore for 1g of oxygen :-

$\large\implies{\sf \frac{16}{6.02×10^{23}}}$

$\large\implies{\sf 2.6×10^{-23}}$

Hence ,

$\underline{\underline{\sf Mass\:of\:1\:atom\:of\:O_2\:is\:2.6×10^{-23}}}$

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b ) Volume of 0.5 mole of oxygen at STP :

We know ,

1 mole = 22.4 litre

Therefore for 0.5 mole volume will be 11.2 litre .

$\underline{\underline{\sf Volume\:of\:0.5mole\:of\:O_2\:is\:11.2litre}}$