Mn or Co is treated with 1 mL of 6 M HNO3 followed immediately by the drop-wise addition of 3% hydrogen peroxide until the precipitate fully dissolves. The test tube is then heated in a water bath until bubbling ceases. At this stage of the experiment, which elements could be found in the resulting LIQUID?

Mn, Co,  H, N and O

Explanation:

When metallic Mn or Co reacts with concentrated HNO₃, they dissolve completely in the acid . The products formed are the nitrates of the metals, water and a mixture of NO and NO₂ gases. Hydrogen peroxide is added to oxidize any NO to NO₂ which is less harmful.

The equations of the reaction are given below;

Mn + HNO₃ > Mn(NO₃)₂ + NO + H₂O

Co + HNO₃ > Co(NO₃)₂ + NO + H₂O

H₂O₂ + NO > H₂O + NO₂

The resulting solution will be the soluble nitrates of manganese and cobalt as well water and this solution contains the following elements; Mn, Co, N, H And O.