Step 1. Calculate the initial concentrations
["H"_2"S"]_0 = "0.29 mol"/"3.0 L" = "0.0967 mol/L" [ H 2 S ] 0 = 0.29 mol 3.0 L = 0.0967 mol/L
Step 2. Write the balanced equation and set up an ICE table.
color(white)(mmmmmmm)"2H"_2"S"color(white)(m) ⇌color(white)(m) "2H"_2 + "S"_2 m m m m m m m 2H 2 S m ⇌ m 2H 2 + S 2
"I/mol·L"^"-1":color(white)(m) "0.096 67" color(white)(mmmm)0 color(white)(mm)0 I/mol⋅L -1 : m 0.096 67 m m m m 0 m m 0
"C/mol·L"^"-1":color(white)(mm) "-"2xcolor(white)(mmmm) "+2"xcolor(white)(m) "+"x C/mol⋅L -1 : m m - 2 x m m m m +2 x m + x
"E/mol·L"^"-1": "0.096 67 - 2"xcolor(white)(lmm) 2xcolor(white)(ml) x E/mol⋅L -1 : 0.096 67 - 2 x l m m 2 x m l x
Write the K_"c" K c expression and solve for x x .
K_"c" = (["H"_2]^2["S"_2])/["H"_2"S"]^2 = 9.30 × 10^"-8" K c = [ H 2 ] 2 [ S 2 ] [ H 2 S ] 2 = 9.30 × 10 -8
((2x)^2×x)/(("0.096 67" – 2x)^2) = 9.30 × 10^"-8" ( 2 x ) 2 × x ( 0.096 67 – 2 x ) 2 = 9.30 × 10 -8
0.09667/(9.30 ×10^"-8") = 1 × 10^"-6" > 400 0.09667 9.30 × 10 -8 = 1 × 10 -6 > 400 . ∴x ≪ "0.099 67" x ≪ 0.099 67
∴ (4x^3)/"0.096 67"^2 = 9.30 × 10^"-8" 4 x 3 0.096 67 2 = 9.30 × 10 -8
4x^3 = "0.096 67"^2 × 9.30 × 10^"-8" = 8.691 × 10^"-10" 4 x 3 = 0.096 67 2 × 9.30 × 10 -8 = 8.691 × 10 -10
x^3 = 2.173 × 10^"-10" x 3 = 2.173 × 10 -10
x = 6.012 × 10^"-4" x = 6.012 × 10 -4
["H"_2] = 2xcolor(white)(l) "mol/L" = 2 × 6.012 × 10^"-4"color(white)(l) "mol/L" = "0.0012 mol/L" [ H 2 ] = 2 x l mol/L = 2 × 6.012 × 10 -4 l mol/L = 0.0012 mol/L
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