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Question
Solve problem:
A student used a carbon pencil to write his homework. The mass of this was found to be 5 mg. With the help of this calculate The number of carbon atoms in 12 mg of his homework writing
Solution
12 mg carbon = 12 × 10–3 g carbon
Number of moles = `"Mass of a substance"/"Molar mass of a substance"`
= `(12xx10^-3 "g")/(12 "g mol"^-1)` = 1 × 10−3 mol
Number of atoms = Number of moles × Avogadro's constant
Number of atoms of carbon = 1 × 10–3 mol × 6.022 × 1023 atoms/mol
= 6.022 × 1020 atoms
Number of atoms of carbon in 12 mg homework writing = 6.022 × 1020 atoms
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