Answer: 2.55 moles
Explanation:
According to avogadro's law, 1 mole of every substance occupies 22.4 L at STP and contains avogadro's number [tex]6.023\times 10^{23}[/tex] of particles.
To calculate the moles, we use the equation:
[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text {Molar mass}}[/tex]
[tex]\text{Number of moles of water}=\frac{45.9g}{18.02g/mol}=2.55moles[/tex]
The rule apply for multiplication and division is :
The least precise number present after the decimal point determines the number of significant figures in the answer. 45.9 has 3 significant figures and 18.02 has 4 significant figures.
Thus the mole of water will be 2.55 moles in three significant figures.
