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4) solve problems

D. Calculate the number of atom in each of the following (Given : Atomic mass of I = 127 u).

a. 254 u of iodine (I)

b. 254 g of iodine (I)

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Given : atomic mass of I=127 u

A. 254 u of iodine (I)

Formula : number of atoms = $$given \space atomic \space mass \space of \space element\over atomic \space mass \space of \space element$$

$$\therefore \space ={254\over 127}$$

=2 atoms

254 u of iodine (I) consist of  2 atoms of I

B. 254 g of iodine (I)

we know the Molar mass of iodine  which is 127 g

Formula :: no of moles =$$given\space mass\over molar \space mass$$

$$\therefore\space = {254\over 127 }=2$$ moles

therefore , number of atoms = n× Avogadro's number

=2$$\times 6.022\times 10^{23}$$ atoms =$$1.2044\times 10^{24} atoms$$

254 g of iodine (I) consist of  $$1.2044\times 10^{24} atoms$$

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