Question

Calculate the number of iron atoms in a piece of iron weighing $2.8g$. (Atomic mass of iron $=56$)

• A. $30.11\times {10}^{23}$ atoms
• B. $3.11\times {10}^{23}$ atoms
• C. $3.0115\times {10}^{22}$ atoms
• D. $301.1\times {10}^{23}$ atoms

Answer 1

The correct option is C $3.0115\times {10}^{22}$ atoms

Given that, weight of iron =2.8 g

Atomic mass= 56

moles of iron$=\frac{\text{wt. of iron}}{\text{atomic mass}}=\frac{2.8}{56}=0.05moles$

1 mole $=6.022\times {10}^{23}atoms$

0.05 moles $=6.022\times 0.05\times {10}^{23}atoms=3.0115\times {10}^{22}$ atoms

Option C is correct.