Question

Determine the mass in grams of 7.55 × 1021 molecules of water H2O.

a.
7.14 × 10-4 g
d.
22.6 g
b.
2.59 x 102 g
e.
2.59 g
C.
0.226 g

Answer 1

Answer: the mass of 7.55 x 10^21 molecules of water is 0.226 g, which corresponds to option (c).

Explanation: The atomic weight of water (H2O) is:

2(1.008 g/mol) + 15.999 g/mol = 18.015 g/mol

Avogadro's number (NA) is:

6.022 x 10^23 molecules/mol

To calculate the mass of 7.55 x 10^21 particles of water, able to utilize the taking after equation:

mass = (number of atoms / Avogadro's number) x atomic weight

mass = (7.55 x 10^21 / 6.022 x 10^23) x 18.015 g/mol

mass = 0.226 g