http://i64.tinypic.com/10mjx4w.jpg - Question 16 why is the answer (c)..?

Let XCln be the fomula of the chloride

No. of moles of AgNO₃ = (0.4 mol/dm³) × (15/1000 dm³) = 0.006 mol
No. of moles of Ag⁺ ions = No. of moles of AgNO₃ = 0.006 mol

Ag⁺(aq) + Cl⁻(aq) → AgCl(s)
No. of moles of Cl⁻ ions = No. of moles of Ag⁺ ions = 0.006 mol

No. of moles of XCln = (0.1 mol/dm³) × (20/1000 dm³) = 0.002 mol

No. of moles of XCln : No. of moles of Cl⁻ ions = 0.002 mol : 0.006 mol = 1 : n
n = 3

Formula of the chloride = XCl₃

..... The answer is : C. XCl₃

n( X chloride) = (0.1 mol/dm³)(20cm³ * 1 dm³ / 1000cm³) = 0.002 mol

AgNO₃(aq) ➞ Ag⁺(aq) + NO₃⁻(aq)

Ag⁺(aq) + Cl⁻(aq) ➞ AgCl(s)
n(Ag⁺) = n(Cl⁻) = (0.4 mol/dm³)(15cm³ * 1 dm³ / 1000cm³) = 0.006 mol

X : Cl = 0.002 : 0.006 = 1 : 3

XCl₃

ans: C
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