Help with chemistry homework please?

[匿名]

2016-05-31 12:56 pm

When solutions containing silver ions and chloride ions are mixed, silver chloride precipitates.

Ag+(aq) + Cl -(aq) AgCl(s) ΔH = -65.5 kJ

a) Calculate ΔH for formation of 0.800 mol of AgCl by this reaction.

(b) Calculate ΔH for the formation of 3.00 g of AgCl.

(c) Calculate ΔH when 0.600 mmol of AgCl dissolves in water.

回答 (1)

fooks

2016-05-31 2:24 pm

✔ 最佳答案

(a)
Ag⁺(aq) + Cl⁻(aq) → AgCl(s) ...... ΔH = -65.5 kJ
When 1 mole of AgCl is formed, ΔH = -65.5 kJ

When 0.800 mol of AgCl is formed :
ΔH = (-65 kJ) × (0.800/1) = -52 kJ

(b)
From Wikipedia, molar mass of AgCl = 143.32 g/mol

Ag⁺(aq) + Cl⁻(aq) → AgCl(s) ...... ΔH = -65.5 kJ
When 143.32 g (1 mole) of AgCl is formed, ΔH = -65.5 kJ

When 3.00 g of AgCl is formed :
ΔH = (-65 kJ) × (3.00/143.32) = -1.4 kJ

(c)
AgCl(s) → Ag⁺(aq) + Cl⁻(aq) ...... ΔH = +65.5 kJ
When 1000 mmol (1 mol) AgCl dissolves in water, ΔH = +65.5 kJ

When 0.600 mmol of AgCl dissolves in water :
ΔH = (+65 kJ) × (0.600/1000) = +0.039 kJ

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