Question

Silver oxide (Ag20) decomposes at temperature 300°C yielding metallic silver and oxygen gas.
A 1.60 g sample of impure silver oxide yields 0.104 g of oxygen gas. What is the per cent by
mass of the silver oxide in the sample ?
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Answer 1

Answer:

Let x be the wight of the pure Ag2O in the 1.60 sample.

The reaction is:

2Ag2O => 4Ag + O2

x/232 moles

moles of O2 would be => x/(232*2)

Weight of O2 => (x/464)*32

Hence, given is the mass of O2 => 0.0689x = 0.104 => x = 1.509 gms

Hence the % by mass of silver oxide is:

=> (1.509/1.60)*100

=> 94.33 %

This is the percentage of pure Ag2O in impure sample.

2AgO—>4Ag+O2

Moles of O2 =0.104/32=0.0325 moles

From the eqn

1 mole of O2 produce 2 mole of AgO

Therefore, 0.0325 moles produce 0.0325×2=0.065 moles of AgO .

molecularmass of AgO =216+16= 232g

Weight of AgO = 0.065×232= 1.508g

Mass% of AgO in sample = (wt .of AgO)×100/total wt. Of sample= 1.508×100/1.6= 94.25%