Question

The no. of neutrons in .0.45g water , assuming that all the hydrogen atoms are H1 atoms and all the oxygen atoms are O16 atoms is:

Answer 1

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Answer 2

Answer : The number of neutrons in 0.45 g of water is $120.44\times 10^{21}$ neutrons.

Solution : Given,

Mass of water = 0.45 g

Molar mass of water = 18 g/mole

First we have to calculate the moles of water.

$\text{ Moles of }H_2O=\frac{\text{ Given mass of }H_2O}{\text{ Molar mass of }H_2O}=\frac{0.045g}{18g/mole}=0.025mole$

1 mole of $H_2O$ has $6.022\times 10^{23}$ molecule of  $H_2O$

0.025 moles of $H_2O$ has $(6.022\times 10^{23})\times (0.025)=15.055\times 10^{21}$ molecule of $H_2O$

Now we have to calculate the number of neutrons in $H_2O$.

The number of neutrons present in 1 molecule of $H_2O$ is,

Number of neutrons in $^1H$ atom = 0

Number of neutrons in $^{16}O$ atom = 8

Total number of neutrons in $H_2O$ molecule = 0 + 8 = 8 neutrons

Number of neutrons present in 1 molecule of $H_2O$ = 8 neutrons

Number of neutrons present in $15.055\times 10^{21}$ molecule of $H_2O$ = $(15.055\times 10^{21})\times (8)=120.44\times 10^{21}$ neutrons

Therefore, the number of neutrons in 0.45 g of water is $120.44\times 10^{21}$ neutrons.