Arjun purchased 250 g of glucose (C6H12O6) for Rs 40. Find the cost of glucose per mole.

Given : 

Mass of urea = 250 g, 

Cost for 250 g glucose = Rs 40, 

Molecular formula of glucose = C₆H₁₂O₆

To find : Cost per mole of glucose.

Calculation : Molecular formula of glucose is (C₆H₁₂O₆). 

Molecular mass of glucose 

= (6 × Average atomic mass of C) + (12 × Average atomic mass of H) + (6 × Average atomic mass of O) 

= (6 × 12 u) + (12 × 1 u) + (6 × 16 u) 

= 180 u 

∴ Molar mass of glucose = 180 g mol^-1

 Number of moles = \(\frac{Mass\,of\,a\,subtance}{Molar\,mass\,of\,a\,subtance}\)

 = \(\frac{250\,g}{180\,g\,mol^{-1}}\)

= \(\frac{250}{180}\) mol

Now,

\(\frac{250}{180}\) mol of glucose cost = Rs 40

1 mol glucose cost = x

∴ x = \(\frac{40\times 180}{250}\)

= Rs 28.8/mol of glucose

∴ The cost of glucose per mole is Rs 28.8.

[Calculation using log table :

\(\frac{40\times 180}{250}\)

= Antilog₁₀[log₁₀(40) + log₁₀(180) + log₁₀(250)]

= Antilog₁₀[1.6021 + 2.2553 – 2.3979] 

= Antilog₁₀[1.4595] 

= 28.80]