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A cylindrical piece of Mg is 10 cm long ...

A cylindrical piece of Mg is 10 cm long and has a diameter of 8 cm. The density of Magnesium is `0.7 gm//cm^(3)`. How many atoms does piece of Mg contain. `[N_(A) = 6 xx 10^(23)]`
[Divide your answer by `22 xx 10^(23)` ]

Text Solution

Verified by Experts

The correct Answer is:
4
Volume of cylindrical piece `= pi r^(2)l`
`= pi xx ((8)/(2))^(2) xx 10`
`= (22)/(7) xx 4 xx 4 xx 10`
`= ((22)/(7) xx 160) cm^(3)`
Mass of piece `= (0.7 xx (22)/(7) xx 160) cm^(3)`
`= (22 xx 16) gm`
Atoms of `Mg = ((22 xx 16)/(24)) N_(A) rArr (44)/(3) N_(A)`
`= (44)/(3) xx 6 xx 10^(23)`
`= (88 xx 10^(23))/(22 xx 10^(23)) = 4`
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Knowledge Check

  • If KOTA CLASSES is writtedn by a graphite pencil, it weighs 3.0 xx 10^(-10) gm. How many carbon atoms are present in it? (N_(A) = 6 xx 10^(23))

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  • The number of electron in 3.1 mg NO_(3)^(-) is ( N_(A) = 6 xx 10^(23) )

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