Question

how many molecules are there in 122 grams of Cu(NO3)2

Answer 1

Answer: $3.9\times 10^{23}$  molecules of $Cu(NO_3)_2$

Explanation:

According to avogadro's law, 1 mole of every substance weighs equal to the molecular mass and contains avogadro's number $6.023\times 10^{23}$ of particles.

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

$\text{Number of moles of} Cu(NO_3)_2=\frac{122g}{187.56 g/mol}=0.65$

1 mole of $Cu(NO_3)_2$ contains=$6.022\times 10^{23}$  molecules of $Cu(NO_3)_2$

Thus 0.65 moles of $Cu(NO_3)_2$ contains=$\frac{6.022\times 10^{23}}{1}\times 0.65=3.9\times 10^{23}$  molecules of $Cu(NO_3)_2$

Thus there are $3.9\times 10^{23}$  molecules of $Cu(NO_3)_2$