1.

A person has as many notes as number of oxygen atoms in 24.8 g Na_(2)S_(2)O_(3).5H_(2)O (mol. Wt. = 248). A note counting machine counts 48 million notes per day. How many days it would take to count thesenotes?

Answer»

`10^(12)`
`10^(14)`
`10^(16)`
`10^(18)`

Solution :`24.8g" of" Na_(2)S_(2)O_(3).5H_(2)O=(24.8)/(248)"mole"=0.1 "mole"`
`"1 mole of "Na_(2)S_(2)O_(3).5H_(2)O" contains O-atoms = 8 MOLES"`
`THEREFORE"0.1 mole of "Na_(2)S_(2)O_(3).5H_(2)O" will contain O-atoms = 0.8 atom"`
`=0.8xx6.02xx10^(23)` atoms
`=4.816 xx10^(23)` atoms
Thus, no. of MASS `=4.816xx10^(23)`
`"Days TAKEN"=(4.816xx10^(23))/(48xx10^(6))=10^(16)`.


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