3.1 mol of $sf(Fe^(3+)$ is mixed with 3.2 mol of $sf(SCN^-)$ and allowed to reach equilibrium, after which 3 mol of $sf([Fe(SCN)]^(2+))$ is formed. What is the value of $sf(K_c)$ ?

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Answer 1 · 2016-06-14T22:31:18

$K_c=150" ""mol".^(-1)."l"$

I am assuming that you mean $NH_(4)SCN_((aq))$ . The $SCN_((aq))^(-)$ ion forms a 1:1 complex with $Fe_((aq))^(3+)$

Construct an $"ICE"$ table:

$" "Fe_((aq))^(3+)" "+" "SCN_((aq))^(-)" "rightleftharpoons" "[Fe(SCN)]_((aq))^(2+)$

$color(red)"I"" "3.1" "3.2" "0$

$color(red)"C"" "-x" "-x" "+x$

$color(red)"E"" "(3.1-x)" "(3.2-x)" "x$

The question tells us that $x=3$

$:.nFe_((aq))^(3+)=3.1-3=0.1$

$nSCN_((aq))^(-)=3.2-3=0.2$

and

$n[Fe(SCN)]_((aq))^(2+)=3$

The expression for $K_c$ is :

$K_c=([Fe(SCN)^(2+)])/([Fe^(3+)][SCN^(-)])$

$:.K_c=(3)/(0.1xx0.2)=150" ""mol"^(-1)."l"$

The question should have specified the temperature as $K_c$ depends on this.

3.1 mol of sf(Fe^(3+)sf(Fe^(3+) is mixed with 3.2 mol of sf(SCN^-)sf(SCN^-) and allowed to reach equilibrium, after which 3 mol of sf([Fe(SCN)]^(2+))sf([Fe(SCN)]^(2+)) is formed. What is the value of sf(K_c)sf(K_c) ?