Question

From 200mg of CO2, 10^21 molecules are removed. How many moles of CO2 are left

Answer 1

Dear student
1 mole of CO₂ = 44g contains 6.022 x 10²³ molecules

Thus 200 mg will contain:
$\frac{0.2}{44}x6.022x{10}^{23}=2.7x{10}^{21}$ molecules

After removal of 10²¹ molecules,

1.7 x 10²¹ molecules will remain,

As 200 mg contains 2.7 x 10²¹ molecules, 1.7 x 10²¹ will weigh

$\frac{200x(1.7x{10}^{21})}{2.7x{10}^{21}}=125.92mg$
Converting milligrams into grams = 125.92 / 1000= 0.12592 g
Calculating the moles left,
Moles= mass of Carbon dioxide/ molar mass of carbon dioxide
Moles = 0.12592 g / 44.01 g/mol
Moles of carbon dioxide left = 0.00286117

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