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Chemistry Question 71 – JEE-MAIN 2026

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An excess of AgNO3 is added to 100 mL of a 0.05 M solution of tetraaquadichloridochromium (III) chloride. The number of moles of AgCl precipitated will be _______ ×10−3. (Nearest integer)

Identify the coordination complex and determine which chloride ions are outside the coordination sphere and thus available for precipitation.

● Video Walkthrough
Step 1: Determine the formula of the complex and dissociable chloride ions.✦ Active

The complex "tetraaquadichloridochromium (III) chloride" has the formula [Cr(H2O)4Cl2]Cl. When dissolved in water, it dissociates into one complex cation and one free chloride ion:

[Cr(H2O)4Cl2]Cl(aq)→[Cr(H2O)4Cl2]+(aq)+Cl−(aq)

Thus, 1 mole of the complex yields 1 mole of precipitable Cl− ions.

Step 2: Calculate the moles of the complex.○ Expand

Given volume = 100 mL=0.100 L.

Given concentration = 0.05 M.

Moles of complex = Concentration × Volume = 0.05 mol/L×0.100 L=0.005 mol.

Step 3: Calculate the moles of AgCl precipitated.○ Expand

Since 1 mole of the complex yields 1 mole of Cl− ions, the moles of Cl− ions available for precipitation are 0.005 mol.

The reaction with AgNO3 is Ag+(aq)+Cl−(aq)→AgCl(s).

Therefore, moles of AgCl precipitated = moles of Cl− ions = 0.005 mol.

To express this in ×10−3: 0.005 mol=5×10−3 mol.

The nearest integer is 5.

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