Question

(a) Calculate the number of moles in 112 g of iron. 

(b) Calculate the mass of 0.5 mole of sugar (C₁₂H₂₂O₁₁ ). 

[Atomic mass of Fe = 56 u, C = 12 u, H = 1 u, O = 16 u]

Answer 1

(a) Given mass: 112g 

Molar mass of iron (Fe) = 56 g/mol 

To calculate the number of moles, we will apply the formula given below:

Number of moles(n) = \(\frac{Given\,mass(m)}{Molar\,mass(M)}\)

Number of moles(n) = \(\frac{112g}{56g/mol}\)

Number of moles = 2

Thus, the number of moles in 112 g of iron is 2.

(b) Given: Number of moles = 0.5 

Molar mass of C₁₂H₂₂O₁₁ = 12 × atomic mass of C + 22 × atomic mass of H + 11 × atomic mass of O 

= 12 × 12 + 22 × 1 u + 11 × 16 u = 342 u or 342 g/mol 

Now, to calculate mass, apply the formula:

Number of moles(n) = \(\frac{Mass(m)}{Molar\,mass(M)}\)

We can write: 

Mass(m) = Number of moles (n) × Molar mass of C₁₂H₂2O₁₁ (M) 

Mass = 0.5 mol × 342g/mol 

Mass = 171g 

Thus, the mass of 0.5 mole of sugar (C₁₂H₂₂O₁₁ ) is 171g.