Question

A cylindrical glass of water (H2O) has a radius of 5.66 cm and a height of 15.8 cm. The density of water is 1.00 g/cm3. How many moles of water are contained in the glass?

Answer 1

The amount of substance (measured in moles) is

$\displaystyle \nu = \frac{m}{\mu}$

where $\mu (H_2O) = 2\cdot A_r(H)+ A_r(O) = 2 \cdot 1 +16 = 18$ g/mol.

Mass can be found from

$m = \rho \cdot V = \rho \cdot \pi r^2 h = 1 \cdot 3.1415 \cdot 5.66^2 \cdot15.8 = 1590$ g

So,

$\nu = \frac{1590 \;g}{18 \; g/mol}= 88.3 \; mol.$

Answer: 88.3 mol