Question

A 0.160-mole quantity of NiCl2 is added to a liter of 1.20 M NH3 solution. What is the concentration of Ni2+ ions at equilibrium? Assume the formation constant* of Ni(NH3)6^2 is 5.5 × 10^8

Answer #1

Initial Moles of NH_{3} = 1.20 mol/L x 1 L = 1.20
Moles

Initial Moles of NiCl2 = 0.160 Moles

The problem reaction can be restated as : Ni^{2+} +
6NH_{3} -->
[Ni(NH_{3})_{6}]^{2+}

Since the formation Constant is very large( of te order
10^{8}), it can be assumed that the entire Ni^{2+}
forms the complex, without any residual Ni^{2+} in the
product. Thus , it can be asserted that the amount of
[Ni(NH_{3})_{6}]^{2+} formed is equal to
the Initial amount of NiCl2,i.e. 0.160 moles.

By stoichiometry, the amount of NH_{3} unconsumed = 1.20
mol - (6x 0.160) = 1.20 - (0.96) = 0.24 moles

Since volume of the solution is constant at 1 L , Concentration will be numerically equal to the number of moles.

K_{f} = [
[Ni(NH_{3})_{6}]^{2+} ]/ [
Ni^{2+}][NH_{3}]^{6}

Using values from above,

5.5x10^{8}= 0.160/ [
Ni^{2+}](0.24^{6})

Solving the Above, we get :

[ Ni^{2+}] = [ 5.5x10^{8} x (0.24^{6}) /
0.160 ] ^{-1}

**[ Ni ^{2+}] = 1.522263 x 10^{-6}
M** at Equillibrium.

A 0.130-mole quantity of CoCl2 is added to a liter of
1.20 M NH3 solution. What is the concentration of
Co2 ions at equilibrium? Assume the formation constant*
of Co(NH3)62+ is 5.0 ×
1031 M–6.
The balanced equation is:
Co2+ + 6NH3 <==>
Co(NH3)62+
The ICE table is:
I: 0.13, 1.2,
0
C:
-x, -6x, +x
E: 0.13-x, 1.2-6x, x
k=[Co(NH3)62+]/[(Co2+)(NH3)6]
5.0x1031=(x)/[(0.13-x)(1.2-6x)6]

1)Which of the following will be more soluble in an acidic
solution than in pure water? PbSO4, Cd(OH)2,AlPO4, CsClO4, AgCl
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solution than in pure water? PbS, AgCl, CsClO4, Zn(OH)2, CaCO3
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NH3 solution. What is the concentration of Ni2 ions at equilibrium?
Assume the formation constant* of Ni(NH3)62 is 5.5 × 108.
____M

The formation constant* of [M(CN)4]2– is 7.70 × 1016, where M is
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After the solution reaches equilibrium, what concentration of
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Express the concentration to two significant figures and include
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