选A N2+3H2=2NH3的平衡常数K=[NH3]2/([N2][H2]3)=a
则 2NH3 =3H2+N2的平衡常数K'=[N2][H2]3/[NH3]2=Kˉ1=aˉ1
所以 NH3 =3/2H2+1/2N2的平衡常数=([N2]1/2[H2]3/2)/[NH3]=K'1/2=aˉ1/2