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

Explanation :-

[tex]\qquad[/tex][tex] \pink{\bf\longrightarrow { Molar \:mass \:of \:H₂O:-} }[/tex]

[tex]\qquad[/tex][tex] \sf \longrightarrow 1\times +16[/tex]

[tex]\qquad[/tex][tex] \sf \longrightarrow 18g[/tex]

[tex]\qquad[/tex]____________________

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

[tex]\qquad[/tex][tex] \purple{\bf\longrightarrow { No \:of \:moles = \dfrac{Given \:mass}{Molar\: mass}}}[/tex]

[tex]\qquad[/tex][tex] \sf \longrightarrow \dfrac{89}{18}[/tex]

[tex]\qquad[/tex][tex] \sf \longrightarrow 4.94\: moles[/tex]

We know –

  • Avogadro number = 6.022×10²³

Number of molecules:-

[tex]\qquad[/tex][tex] \purple{\bf \longrightarrow No \: of \: moles \times Avogadro \: number}[/tex]

[tex]\qquad[/tex][tex] \sf \longrightarrow 4.94×6.022×10²³[/tex]

[tex]\qquad[/tex][tex] \sf \longrightarrow 2.98 ×10²⁴[/tex]

[tex]\qquad[/tex][tex]\purple{ \bf \longrightarrow 2.98×10²⁴ molecules}[/tex]

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

[tex]\qquad[/tex]____________________

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