1) HCl consists of one H and Cl atom separated by 0.127 nm, the bond length. The

Question

1)

HCl consists of one H and Cl atom separated by 0.127 nm, the bond length. The Cl atom has a partial charge of -0.177e and the H atom has a partial charge of +0.177e, where e = 1.602x10-19 C is the electron charge.

What is the dipole moment of the molecule?

C*m

2)

Now the HCl molecule is placed near a sodium ion Na+ with charge +1e. As shown in the figure, the distance between the Cl and Na atoms is d = 2 nm.

What is the magnitude of the total force on the HCl molecule due to the Na+ ion |FHCl|?

N

3)

Compare your previous answer to the force on a single Cl- ion with charge -1e due to the Na+ ion 2 nm away.

What is the ratio of the force on the Cl- ion to the force on the HCl molecule |FCl-/FHCl|?

Explanation / Answer

1)
dipole moment = q*d
= (0.177e)((0.127 nm)
= (0.177*1.6*10^-19 C)*(0.127*10^-9 m)
= 3.6*10^-30 Cm

2)
q1 = 0.177*1.6*10^-19 C = 2.832*10^-20 C
q2 = 1.6*10^-19 C
d = 2nm = 2*10^-9 m

F = K*q1*q2/d^2
= (9*10^9)*( 2.832*10^-20 )*(1.6*10^-19 ) /(2*10^-9)^2
=1.02*10^-11 N

3)
q1 = -1.6*10^-19 C
q2 = 1.6*10^-19 C
d = 2nm = 2*10^-9 m

FCl- = K*q1*q2/d^2
= (9*10^9)*( 1.6*10^-19 C)*(1.6*10^-19 ) /(2*10^-9)^2
=5.76*10^-11 N

ratio = 5.76*10^-11 / 1.02*10^-11
= 5.65

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