The percentage composition of the alloy : 19.35% Zn, 80.65%Ag
Further explanation
Given
2.55 gram of an alloy
170 cc (170 ml=0.17 L) of Hydrogen gas(H₂)
Ar Zn = 65. H=1
Required
The percentage composition
Solution
Silver remained unsolved⇒no reaction
Hydrogen gas from reaction of Zn
Zn+2HCl⇒ZnCl₂ + H₂
mol H₂ at STP (STP⇒1 mol = 22.4 L) :
[tex]\tt \dfrac{0.17}{22.4}=0.00759~moles[/tex]
From equation, mol ratio Zn : H₂ = 1 : 1, so mol H₂ = 0.00759
Mass Zn :
[tex]\tt mass=mol\times Ar\\\\mass=0.00759\times 65\\\\mass=0.49335~g[/tex]
Mass Silver :
[tex]\tt 2.55-0.49335=2.05665~g[/tex]
Percent composition :
[tex]\tt \dfrac{0.49335}{2.55}\times 100\%=19.35\%[/tex]
[tex]\tt \dfrac{2.05665}{2.55}\times 100\%=80.65\%[/tex]
