\begin{array}{|c|ccccc|}\hline \text{}&\text{$N_{2}$}&\text{+}&\text{$3H_{2}$}&\text{$\rightleftharpoons$}&\text{$2NH_{3}$}\\\hline \text{Bđầu}&\text{0,21}&\text{}&\text{2,6}&\text{}&\text{}\\\hline \text{Pứng}&\text{x}&\text{}&\text{3x}&\text{}&\text{2x}\\\hline \text{CB}&\text{0,21-x}&\text{}&\text{2,6-3x}&\text{}&\text{2x}\\\hline \end{array}

Ta có: `K_c=([NH_3]^2)/([H_2]^3 . [N_2])` nên

`((2x)^2)/((2,6-3x)^3 . (0,21-x))=2`

`4x^2=2(2,6-3x)^3 . (0,21-x)`

`4x^2-2(2,6-3x)^3 . (0,21-x)=0`

`=>x=0,2` (Bấm máy) (tm)

Nhập máy: `[4x^2-2(2,6-3x)^3 . (0,21-x)]:(x-0,2)`

Bấm Shift `->` Solve `=>x≈1,36>0,21` (ktm)

`=>{([N_2]_(cb)=0.21-0.2=0.01),([H_2]_(cb)=2.6-3 xx 0.2=2),([NH_3]_(cb)=2 xx 0.2=0.4):}`

`->bbB`