Question

Which has the maximum number of atoms?
(A) 24 g of C (12)
(B) 56 g of Fe (56)
(C) 27 g of Al (27)
(D) 108 g of Ag (108)

Answer 1

To calculate the number of atoms first we have to calculate the number of moles of the given elements. Then the number of atoms will be equal to the product of the number of moles and Avogadro’s number.

Complete step by step solution:
The mole is a measurement or it is the basic unit which helps to calculate the amount of substance present in the given sample. 1 mole of a number is equal to Avogadro’s constant${{N}_{A}}$.
For carbon-
Given mass of carbon = 24g
Molar mass of carbon= 12 g
Number of mol is calculated by ratio of given mass to the molar mass.
Number of mol of sodium = $\dfrac{\text{given mass}}{\text{molar mass}}$
After putting the value we get,
Number of mol of carbon = $\dfrac{24}{12}=2$moles
And, number of atoms= $\left( \text{number of moles} \right)\text{X }\left( {{N}_{A}} \right)$
= 2 ${{N}_{A}}$ atoms (${{N}_{A}}$=$6.022X{{10}^{23}}$)
For iron-
Given mass of iron = 56 g
Molar mass of iron= 56 g
Number of mol of iron = $\dfrac{56}{56}=1$moles
And, number of atoms= $\left( \text{number of moles} \right)\text{X }\left( {{N}_{A}} \right)$
= 1 ${{N}_{A}}$ atoms (${{N}_{A}}$=$6.022X{{10}^{23}}$)
For aluminium-
Given mass of Al = 27 g
Molar mass of Al= 27 g
Number of mol of Al = $\dfrac{27}{27}=1$moles
And, number of atoms= $\left( \text{number of moles} \right)\text{X }\left( {{N}_{A}} \right)$
= 1 ${{N}_{A}}$ atoms (${{N}_{A}}$=$6.022X{{10}^{23}}$)
For silver-
Given mass of Ag = 108 g
Molar mass of Ag= 108 g
Number of mol of Ag = $\dfrac{108}{108}=1$moles
And, number of atoms= $\left( \text{number of moles} \right)\text{X }\left( {{N}_{A}} \right)$
= 1 ${{N}_{A}}$ atoms (${{N}_{A}}$=$6.022X{{10}^{23}}$)

Hence the correct option is (A) 24 g of carbon

Note: If the question asks you to find the exact number of atoms then put the value of ${{N}_{A}}$ and write the exact number of atoms. 1 mole=$6.022X{{10}^{23}}$ particle or atoms or molecules or electrons or protons etc.