Question

An atom of some element X weighs $6.644\times {10}^{-23}$g. Calculate the number of gram-atoms in 40 kg of it.

• A. 0.0038
• B. 0.0028
• C. 0.028
• D. 0.238

Answer 1

Answer: (B)

0.0028

Molecular mass of $C{O}_2=12+2\times 16$ = 44

Total no. of moles in 200mg $C{O}_2$

= $\frac{Massof{C}_{O}2}{Molecularmass}$

= $200$ × ${10}^{-3}$ $g/44$

$=0.00454$

No. of moles removed

= $\frac{{10}^{21}}{6.022\times {10}^{23}}$

= 0.00166

No. of moles of $C{O}_2$left

= 0.00454 – 0.00166

= $0.00288$