Question

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

b) Calculate the mass of 0.5 mole of sugar (C12H22O11) (1½)

(Given – Atomic mass of Fe = 56u , C = 12u , H = 1u , O = 16u)​

Answer 1

a) Given mass of Iron = 112 grams

Atomic mass of Fe = 56 u

$n = \dfrac{given \: mass}{molar \: or \: atomic \: mass}$

where n is number of moles.

$\implies \: n = \dfrac{112}{56}$

$\implies \: n = \dfrac{2}{1}$

$\implies \: n = 2$

Number of moles in 112 g of iron = 2

________________________

b) moles of sugar = 0.5

Molecular mass sugar (C12H22O11) = 12 (mass of C)+22(mass of H)+11(mass of O)

= (12×12)+(22×1)+(11×16)

= 144+22+176

= 342 u

$\: mass \: = n \times molecular \: mass$

Where n is number of moles

$\implies \: mass = 0.5 \times 342$

$\implies \: mass = \dfrac{5}{10} \times 342$

$\implies \: mass = \dfrac{1710}{10}$

$\implies \: mass = 171g$

mass of 0.5 mole of sugar = 171 grams