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Solid State

Section: Chemistry

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Question : 42 of 69

Marks: +1, -0

10 mL of 1 mM surfactant solution forms a monolayer covering

0.24\,\text{cm}^2

on a polar substrate. If the polar head is approximated as a cube, what is its edge length?

[9 Apr 2019 Shift 2]

2.0 pm
0.1 nm
2.0 nm
1.0 pm

Solution:

Given the surtactrant solution has molar concentration is

10^{-3}\,\text{M}

. Volume ofsolution = 10mL

\therefore

no. of moles of surtactant

=10\times10^{-3}\times10^{-3}

moles

=10^{-5}

moles

No. of polarheads =

6\times10^{23}\times10^{-5}

=6\times10^{18}

Area coverd on polar substrate

=0.24 \times 10^{4} \, \text{m}^2

a^{2} \times 6 \times 10^{18}=2.4 \times 10^{-5}

a^{2}=4 \times 10^{-24}

a=2 \times 10^{-12} \, \text{m}

\therefore a=2.0 \, \text{pm}

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