Question

How many atoms are present in 8.78 grams O2?

Answer 1

Moles of O_2

• Given mass/Molar mass
• 8.78/32
• 0.27mol

No of atoms

• No of moles×Avagadro no
• 0.27×6.023×10²³
• 1.6×10²³atoms

Answer 2

Note the formula

$\boxed{\sf No\:of\:atoms=No\:of\:moles\times Avagadro\:no}$

Find no of moles

$\\ \tt{:}\dashrightarrow \dfrac{8.78g}{32g/mol}$

$\\ \tt{:}\dashrightarrow 0.27mol[tex]

No of atoms

[tex]\\ \tt{:}\dashrightarrow 0.27\times 6.023\times 10^{23}$

$\\ \tt{:}\dashrightarrow 1.6\times 10^{23}atoms$