Question

One atom of element weigh 6.643×10^-23g.No of moles in 20kg is

Answer 1

Mass of atom: 6.643×6.023 = 40

So, 1 mole = 40gm

Hence x mole = 20,000

So, x = 20,000/40

= 500 moles.

Answer 2

❒ Given Mass is 20kg and Weight of an element is $\sf 6.543 \times 10^{-23} \: g.$

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Converting 20kg into grams.

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$:\implies\sf 20 \times 10^{3} g$

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Now,

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$:\implies\sf GAM = N_{a} \times 6.643 \times 10^{-23} g$

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Here, GAM is Gram atomic mass and $\sf N_{a}$ is Avogadro Number constant.

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Therefore,

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$:\implies\sf GAM = N_{a} \times 6.643 \times 10^{-23} g \\\\\\:\implies\sf 6.022 \times 10^{23} \times 6.643 \times 10^{-23} \\\\\\:\implies{\underline{\boxed{\frak{\pink{40}}}}}\;\bigstar$

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❒ Now, total number of Moles:

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$:\implies\sf \dfrac{20\times10^{3}}{40}\\\\\\:\implies\sf \dfrac{20 \times 1000}{40}\\\\\\:\implies\sf \cancel\dfrac{20000}{40}\\\\\\:\implies{\underline{\boxed{\frak{\pink{500}}}}}\;\bigstar$

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$\therefore{\underline{\sf{Hence,\;the\: number \;of\: moles \;of\; an \;element\; x\; in \;20 \;Kg\; is \; \bf{500}.}}}$