Question

Calculate the number of water molecules present in one drop of water which weighs
0.18 g.

TNSCERT Class 10 Chemistry Ch 10 Atoms and Molecules

Answer 1

number of moles,n = w/M
w= 0.18 g
M of H2O= 18 g
∴n = 0.18/18 = 0.01
1 mole contains 6.023×10²³ molecules
∴0.01 mole contains (6.023×10²³)×0.01 = 6.023×10^21 molecules

Answer 2

Answer:

There are $6.022\times 10^{21}$ molecules of water.

Explanation:

Mass of water drop =0.18 g

Molar mass of water=,18 g/mol

Mole of water in a drop:

$\frac{0.18 g}{18 g/mol}=0.01 mol$

Number of water molecules in 0.18 g of water drop:

$0.01 mol\times 6.022\time 10^{23} molecules=6.022\times 10^{21} molecules$

There are $6.022\times 10^{21}$ molecules of water.