Question

number of protons present in 0.155 gram of phosphorus is

Answer 1

0.075Na (Na=Avogadro's constant)

Answer 2

Answer : The number of protons in 0.155 g of phosphorous is $4.51\times 10^{18}$ protons.

Solution : Given,

Mass of phosphorous = 0.155 g

Molar mass of phosphorous = 18 g/mole

First we have to calculate the moles of phosphorous.

$\text{ Moles of }P=\frac{\text{ Given mass of }P}{\text{ Molar mass of }P}=\frac{0.155g}{31g/mole}=0.005mole=5\times 10^{-3}moles$

1 mole of phosphorous has $6.022\times 10^{23}$ molecule of phosphorous

$5\times 10^{-3}$ moles of phosphorous has $(6.022\times 10^{23})\times (5\times 10^{-3})=30.11\times 10^{20}$ molecule of phosphorous

Now we have to calculate the number of protons in phosphorous.

The number of protons present in 1 molecule of phosphorous is,

Atomic number = Number of protons = Number of electrons = 15

Number of protons present in 1 molecule of phosphorous = 15

Number of protons present in $30.11\times 10^{20}$ molecule of phosphorous = $15\times 30.11\times 10^{20}=4.51\times 10^{18}$ protons

Therefore, the number of protons in 0.155 g of phosphorous is $4.51\times 10^{18}$ protons.