Question

How many molecules are present in a sample that is 89 g of H2O?

Answer 1

• Mass of H₂O (water) is 89 g and we are asked to find number of molecules present in 89 g of H₂O.

Step-by-step explanation :-

`\qquad`
`\pink{\bf\longrightarrow { Molar \:mass \:of \:H₂O:-} }`

`\qquad`
`\sf \longrightarrow 1* +16`

`\qquad`
`\sf \longrightarrow 18g`

`\qquad`____________________

Let's calculate the number of moles present in 89g of H₂O.

`\qquad`
`\purple{\bf\longrightarrow { No \:of \:moles = (Given \:mass)/(Molar\: mass)}}`

`\qquad`
`\sf \longrightarrow (89)/(18)`

`\qquad`
`\sf \longrightarrow 4.94\: moles`

We know –

• Avogadro number = 6.022×10²³

Number of molecules:-

`\qquad`
`\purple{\bf \longrightarrow No \: of \: moles * Avogadro \: number}`

`\qquad`
`\sf \longrightarrow 4.94×6.022×10²³`

`\qquad`
`\sf \longrightarrow 2.98 ×10²⁴`

`\qquad`
`\purple{ \bf \longrightarrow 2.98×10²⁴ molecules}`

• Thus, 2.98×10²⁴ molecules are there in 89g of H₂O.

`\qquad`____________________