Which of the following pairs of cations will turn borax beads blue in an oxidising flame?

CHEMISTRY · Single correct · ICSE · Chemistry · Analytical Chemistry · Analytical Chemistry

Problem

Which of the following pairs of cations will turn borax beads blue in an oxidising flame? (1)

\text{Fe}^{2+}

and

\text{Co}^{2+}

(2)

\text{Co}^{2+}

and

\text{Cu}^{2+}

(3)

\text{Cu}^{2+}

and

\text{Mn}^{2+}

(4)

\text{Cu}^{2+}

and

\text{Cr}^{3+}