There are two crystalline forms of PbO ;
one is yellow and the other is red. The
standard enthalpies of formation of
these two forms are −217.3 and −219
kJ per mole respectively. Calculate the
enthalpy change for the solid-solid
phase transition.
PbO (yellow) → PbO (red)
If A, B, C are the angles of a triangle,
then 2sin(A/2)cosec(B/2)sin(C/2) − sinAcot(B/2)
− cos A is
(1) Independent of A, B, C
(2) Function of A, B, C
(3) Function of A, B
(4) Function of B, C