$EDTA$ combines with metal cations to form:

In the test of $NO_3^-$ ion,a dark brown ring complex is formed. Which of the following statements is incorrect regarding this complex?

$3$ moles of a metal complex with the formula $Co(en)_2 Cl_3$ gives $3$ moles of silver chloride on treatment with an excess of silver nitrate. The secondary valency of $Co$ in the complex is $.....$ (Round off to the nearest integer).

What is the number of $N$ atoms present in $EDTA$?

Which of the following complexes gives only $25\%$ mole of $AgCl$ precipitate when reacted with excess $AgNO_3$?

What is the number of $=N-OH$ groups present in dimethyl glyoximato?