What are the oxidation states of phosphorus in the following:

Let the oxidation state of $p$ be $x$.

(i) H3PO3 

$3+x+3(-2)=0$

$3+x-6=0$

$x-3=0$

$x=+3$

(ii) PCl3 

$x+3(-1)=0$

$x-3=0$

$x=+3$

(iii) Ca3P2

$3(+2)+2(x)=0$

$6+2 x=0$

$2 x=-6$

$x=-3$

(iv) Na3PO4

$3(+1)+x+4(-2)=0$

$3+x-8=0$

$x-5=0$

$x=+5$

(v) POF3

$x+(-2)+3(-1)=0$

$x-5=0$

$x=+5$