Question

Find out the number of each atom present in 3.42g sucrose (C₁₂H₂₂O₁₁).

Answer 1

 Molecular weight of sucrose C₁₂H₂₂O₁₁ 

= 12 × 12 + 22 × 1 + 11 × 16 

= 144 + 22 + 176 = 342 g 

∵ 342 g sucrose contains = 6.022 × 10²³ 

 ∴ 3.42 g sucrose will contain 

\( = \frac{6.022\times10^{23}\times 3.42}{342}\)

= 6.022 × 10²¹ molecules 

∵ 1 molecule of sucrose = 12 carbon atoms

 ∴ 6.022 × 10²¹ molecules of sucrose will contain 

= 12 × 6.022 × 10²¹ carbon atoms 

= 72.24 × 10²¹ carbon atoms 

= 7.224 × 10²² C atoms 

∴ 1 molecule of sucrose = 22 hydrogen atoms 

∵ 6.022 × 10²¹ molecules of sucrose will contain 

= 22 × 6.022 × 10²¹ 

= 132.44 × 10²¹ H atoms 

= 1.32 × 10²³ H atoms 

∵ 1 molecule of sucrose = 11 oxygen atoms 

6.022 × 10²¹ molecules of sucrose will contain 

= 11 × 6.022 × 10²¹ oxygen atoms 

 = 6.622 × 10²¹ O-atoms 

= 6.622 × 10²² O-atoms