Question

Which of the following correctly represents 360 g of water?

i. 2 moles of H₂O

ii. 20 moles of water

iii. 6.022 x 10²³ molecules of water

iv. 1.2044 x 10²⁵ molecules of water

A. i

B. I and iv

C. ii and iii

D. ii and iv

Answer 1

20 moles of water:

Given: Number of moles = 20

Atomic mass of H₂O = 2 × 1 + 16 = 18g/mol

To find out the mass of water, apply the formula given:

Number of moles = \(\frac{Mass}{Molar\,mass}\)

⇒20 = \(\frac{mass}{18\,g/mol}\)

⇒ Mass = 20 mol × 18g/mol

⇒ Mass = 360 g

1.2044 x 10²⁵ molecules of water:

1 mole = 6.022 × 10²³

1.2044 x 10²⁵ molecules = \(\frac{1.2044\times10^{23}}{6.022\times10^{23}}\)

⇒20 moles

Mass of 20 moles of water is 360g.

Thus, option D is correct.